Structuras August2024.pdf mes de octubre

artículos variados sobre calculo estructural

1. steel
Biomimicry
in Design
ATLAS TUBE EXPANDS ITS
When Las Vegas’ most iconic entertainment venue required difficult-to-source HSS
to meet its lofty goals, Atlas Tube rose to the occasion. Since its debut in September
2023, Las Vegas’ Sphere at the Venetian Resort has drawn audiences from around
the world seeking an immersive experience that engages all senses.
atlastube.com
Photo Credit: Sphere Entertainment
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INSIDE: Biomimicry at The Leaf 30
Circular Construction 10
Washington Univ. Research Building 48
Changes to ASCE 7-22 Flood Loads53STRUCTURE
AUGUST 2024
NCSEA | CASE | SEI

2. ATLAS FABRICATES THE FUTURE
The venue’s massive, semispherical frame sits just south of
Sands Avenue and east of Las Vegas Boulevard. The
Sphere’s revolutionary design takes up 750,000
square feet and comfortably seats 18,500
concertgoers. It boasts an eye-catching
steel frame that has quickly become a
landmark representative of the world-class
entertainment and recreation that
Las Vegas has to offer.
To meet the Sphere’s aesthetic
requirements, the engineering design
called for unique sizes of round
hollow structural sections (HSS).
Atlas Tube was chosen as a partner
due to its ability to quickly tool up,
produce, and deliver those unique
sizes within North America.
Atlas’ Engineering Support team had
worked with fabricator W&W | AFCO
on challenging projects before, and
the existing partnership paved the way
for collaboration that made the project a
success. Achieving the intended vision of the
Sphere required HSS sizes that are listed in the
AISC Steel Manual but have never been rolled by
Atlas Tube. Atlas invested in the necessary tooling
to create the full range of required sizes for W&W,
ultimately producing 2,460 tons of HSS for the project.
The strict quality standards of Atlas’ 100% domestically made steel
combined with its wealth of experience and expertise with custom tooling
and logistics helped W&W | AFCO deliver the project on time.
750,000
SQUARE FEET
18,500
SEATS
2,460
TONS OF HSS
Photo Credit: Sphere Entertainment
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Scan for a downloadable copy of the project highlight. More on the design and
engineering of Las Vegas’ Sphere is covered in Modern Steel Construction and
Informed Infrastructure. To learn more about Atlas or to discuss your design
ambitions, call 800.733.5683 or visit atlastube.com
Owner: Sphere
Entertainment Company
General Contractor:
MSG LV Construction LLC
Architect: Populous
Structural Engineer:
Severud Associates
Erection Engineer:
Stanley D. Lindsey and
Associates Ltd.
Steel Team
Fabricator and Erector:
W&W | AFCO Steel
Detailer: Prodraft Inc.
Bender-Rollers: Max Weiss Co.;
Chicago Metal Rolled Products
Casting Manufacturer:
Cast Connex
Though simple from the outside, the Sphere is composed
of several interacting structural systems:
• A pile-supported foundation
• A structure supporting interior seating and vertical
transportation
• The parametrically designed exterior skeleton, known
as the geosphere
• A domed roof below the geosphere that supports an
all-encompassing screen over the concert venue
The round HSS members of the geosphere are connected
to custom nodes produced by Cast Connex, which
reduced fabrication cost and provided precise, repeatable
geometry at each of the many connection points.
These parts work in perfect balance to create a unique,
jaw-dropping superstructure that greatly benefits from the
HSS compact profile and its unique ability to accomplish
the engineering and architectural goals of the project.
In addition to the Sphere itself, the venue features a
1,200-foot-long off-site pedestrian bridge with a unique
serpentine pattern that connects the Sphere to the larger
Las Vegas Strip. The bridge features a metal walking
deck and a metal deck roof, founded on pipe piles just
like the Sphere.
Ultimately, Atlas Tube’s ability to quickly set up custom
tooling for uncommon sizes of HSS, close relationships
with fabricators, and its speed of delivery helped to make
the Sphere one of the world’s premier concert venues
and a contemporary American icon.
PARTNERS
Photo Credit: Sphere Entertainment
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3. 3AUGUST 2024
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Claremont Engineers Inc., Oakland, CA
[email protected]
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Schaefer, Cincinnati, Ohio
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AISC, Littleton, CO
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Walter P Moore, Houston, TX
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Pennoni, Pittsburgh, PA
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Vice President Engineering & Advocacy, Masonry
Concrete Masonry and Hardscapes Association (CMHA)
Jessica Mandrick, PE, SE, LEED AP
Gilsanz Murray Steficek, LLP, New York, NY
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Cool Country Engineering PLLC,Cabot, AR
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Cast Connex Corporation, Davis, CA
Evans Mountzouris, PE
Retired, Milford, CT
Kenneth Ogorzalek, PE, SE
KPFF Consulting Engineers, San Francisco, CA (WI)
John “Buddy” Showalter, PE
International Code Council, Washington, DC
Eytan Solomon, PE, LEED AP
Silman, New York, NY
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Architect: Pelli Clarke & Partners, and
Adamson Associates
Structural Engineer: Thornton Tomasetti,
and Schlaich Bergermann Partner
Structural Steel: Skanska
Photography by Jason O’Rear Photography
CUSTOM CASTING
Scan the QR-Code
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1 2 3
1
2
3

5. AUGUST 2024 5
FEATURES
Contents
AUGUST 2024
MULTI-PURPOSE MARVEL
By Kevin Shelley, AIA, LEED AP, Scott Clore, PE, and Michael Roach, PE
Structural engineers and architects collaborated on a year-round
multi-purpose venue at Indiana’s historic pavilion.
38
SUPPORTING A COMMUNITY AT
ASTERI ITHACA By Cody Gibbens, PE
The project delivered a conference center as well as affordable housing to
the growing city.
44
BIOMIMICRY AT THE LEAF
By David Bowick, P.Eng.
The structural systems and details of “The Leaf" at Canada’s Diversity
Gardens, Assiniboine Park in Winnipeg, reflect biophilic design.
30
READY TO MEET
CHANGING NEEDS
By Kurt Bloch, SE, and Julie Shaw, PE
The structural systems at the new Washington University School of
Medicine Jeffrey T. Fort Neuroscience Research Building needed to
accommodate ever-evolving needs of the research groups.
48

7. AUGUST 2024 7
Publication of any article, image, or advertisement in STRUCTURE
®

magazine does not constitute endorsement by NCSEA, CASE,
SEI, the Publisher, or the Editorial Board. Authors, contributors,
and advertisers retain sole responsibility for the content of their
submissions. STRUCTURE magazine is not a peer-reviewed
publication. Readers are encouraged to do their due diligence
through personal research on topics.
COLUMNS and DEPARTMENTS
In Every Issue
3 Advertiser Index
62 Industry News
66 NCSEA News
68 CASE in Point
70 SEI Update
70 Anchors Guide
16
62
10
56
Codes & Standards
Balustrade Design Loads: Failures, Fatalities, Research, & Global Design Practices
By Richard Green, SE, PE, P.Eng.,CPEng, IntPE
53
Code Updates
Major Changes to ASCE 7-22 Flood Loads
By William L. Coulbourne, PE; Daniel Cox, Ph.D; and Jessica Mandrick, PE, SE
24
Structural Design
Equilibrium Without Statics
By Edmond Saliklis, Ph.D, PE
20
Structural Design
New Design Tools Available for CLT
By Matt Kantner, PE, SE
16
Structural Sustainability
Designing New Structures for Deconstruction to Get a Circular Economy
By Steven Anastasio, PE
10
Structural Sustainability
Circular Construction By Alexis Feitel, PE, and Dan Bergsagel, C.Eng., MICE
9
Editorial
Giving Back Through Disaster Response By Andrew Lovenstein, PE, SI
59
Codes & Standards
The Gold Standard in Steel Design
By Margaret Matthew, PE, and Yasmin Chaudhry, PE
73
Structural Forum
Improv and the Engineer
By Mark Riley, Ph.D.
28
Structural Influencers
Duane Miller

9. STRUCTURE magazine AUGUST 2024 9
O
ne of the things that I enjoy about being
a professional engineer is the sense of
community. As with all communities, there
is a social contract where along with the ben-
efits to be gained is a responsibility to give
back. The benefits gained include sharing our
collaborative knowledge to strengthen build-
ing codes and industry standards, as well as
receiving continuing education to keep cur-
rent with our profession. As for giving back
to the community, one way that I’ve found to
help our larger community is through disaster
response. There are two primary ways to help
with disaster response, and I have been active
in both for many years.
SEER Responder
When a natural disaster has a large area of
effect, many buildings may become damaged.
The local Building Departments, as well as state
or regional Emergency Operations Centers
have to check buildings to make sure they are
habitable and/or have to be evacuated
until repairs are made. SEER volunteers
make a quick evaluation of the homes or
commercial structures, notify the owners
of the building’s status, and provide that
status to the local Building Department.
How to Join: The first step is to take
one of two classes on how to evaluate
structures. One class is “When Disaster
Strikes,” presented by The International
Code Council (ICC). The other class
is the California Office of Emergency
Services’ Safety Assessment Program.
These classes are offered several times
a year by industry groups, including
local state structural engineers associa-
tions. NCSEA offers training through its
CalOES Safety Assessment Program, which
is compliant with the requirements of the
Federal Resource Typing Standards for engi-
neer emergency responders. The next training
will take place this fall.
The ICC and NCSEA together created the
Disaster Response Alliance, which maintains a
single, national database of skilled volunteers
willing to help with response and recovery
activities. After taking one of the two classes
on how to evaluate structures, a volunteer can
sign up to be placed in this database, which
is located at the Disaster Response Alliance
website: Disasterresponse.org/register.
How the Process Works: After a natural
disaster, the local Building Departments
or Emergency Operation Centers (AHJ)
determine how many SEER volunteers will
be needed. They will then reach out to the
Disaster Response Alliance, which will review
the database of volunteers. After the volunteer
has been contacted and agreed to be deployed,
they will travel to the area of the natural disaster
and work with the Building Departments to
evaluate the buildings. The inspection plan and
locations will be provided to the volunteers by
the local Authority Having Jurisdiction (AHJ).
The volunteers will conduct their inspections
on the structures designated by the AHJ and
report their data back to the AHJ each evening.
Typical deployment occurs a couple weeks after
the natural disaster for a week or two.
Who Can Volunteer: A volunteer does
not have to be a Professional Engineer, but
Professional Engineers are greatly appreciated. A
volunteer must complete one of the two classes
listed above, and the volunteer must be signed
up on the Disaster Response Alliance database.
USAR Responder
Urban Search and Rescue (USAR) teams
deploy after natural disasters, such as earth-
quakes and hurricanes. They also respond after
a building collapses. The teams are organized
by individual states. Some state teams are also
designated to be Federal Government FEMA
teams. USAR teams are typically made up of
firefighters who conduct rescue operations,
as well Structural Specialists, who assist the
rescuers with the evaluation of buildings,
monitor damaged buildings while rescue
efforts are under-
way, and provide
advice on shoring
damaged elements
of the structure so
that the rescuers are
in the safest conditions possible. Other special-
ists on a USAR team include medical doctors,
rescue dog handlers, experts in crane lifting,
and drone pilots.
How to Join: The first step is to find the
closest Urban Search and Rescue team. Every
USAR team has a lead Structural Specialist
whose name can be found by contacting the
USAR team. A volunteer should contact the
Lead Structural Specialist and express interest
in joining the team.
After joining a team, the volunteer will be
sent to Structural Specialist Training con-
ducted by the U.S. Army Corps of Engineers.
This training is a week-long class focused on
using building monitoring equipment, shor-
ing techniques and guidelines, and hands-on
experience in conducting building evaluations
and search operations.
How the Process Works: After a natu-
ral disaster or building collapse, states and
FEMA will activate the USAR teams. This
can actually occur before the disaster, in the
case of a hurricane. The Structural Specialists
deploy with the rescue teams to conduct
search and rescue operations. Some FEMA
teams deploy internationally for disaster
response, as well. When a USAR team is
activated, the team and all its gear are loaded
onto transportation and sent to the affected
area. A typical deployment can last between
one and three weeks.
Who Can Volunteer: A volunteer must
be a professional engineer with experience
in buildings, construction, and building
evaluations.
Disasters happen, and we as engineers are
uniquely qualified to help save additional
lives and infrastructure by ensuring rescue
and recovery efforts are performed safely.
Volunteering is rewarding both on a profes-
sional and personal level. ■
EDITORIAL
Giving Back Through Disaster Response
By Andrew Lovenstein, PE, SI
Andrew Lovenstein, PE, SI, is a Senior Engineer at J.S. Held
LLC in Ft Lauderdale, FL. He has extensive experience
evaluating the structural condition of existing buildings and
has performed evaluations after hurricane, flood, fire, vehicle
impact, mold, and sinkhole activity.
Engineers are needed as disaster response volunteers to help with
building evaluations.

10. STRUCTURE magazine 10
Circular
Construction
A city-owned site in Boulder, Colorado, is a success
story for deconstruction, stockpiling, and reuse of
structural steel.
By Alexis Feitel, PE, and Dan Bergsagel, C.Eng., MICE
structural SUSTAINABILITY
B
oulder, Colorado, is one North American city advancing circu-
lar economy practices. Aiming to reduce its emissions by 80%
by 2050 and become “zero-waste,” Boulder passed Deconstruction
Ordinance 8366 in 2020, which requires residential and commercial
deconstruction projects to divert 75% of materials by weight from
landfills, via recycling or reuse. This case study describes Boulder’s
exemplary circular economy project, focusing on the deconstruction,
stockpiling, and reuse of salvaged structural steel from the Boulder
Community Hospital for Boulder’s new Fire Station 3.
A circular economy prioritizes sharing, leasing, reusing, repairing, and
recycling existing materials and products (i.e. structural components)
for as long as possible, reducing environmental impacts compared to
the prevailing linear economy, which relies on a limitless supply of
cheap, easily accessible materials and energy. Extending the lifecycle
of construction products prevents waste to landfill, resource extrac-
tion, and embodied carbon emissions associated with manufacturing.
Often, buildings are demolished and their components landfilled—
not because they are in deterioration but because they have lost their
aesthetic or functional value. Many buildings are deemed too costly
to convert to a new occupancy type, requiring major structural modi-
fications and material replacement. The building may no longer have
value, but what about its components?
Components such as structural steel beams and columns can be
recovered through deconstruction, which is the intentional disassembly
of a building or structure to prevent damage to components. Although
a typical hot-rolled structural steel section contains 93% recycled
content on average, 89% of the product’s manufacturing emissions are
attributed to the melting and processing of the raw material, billet cast-
ing, and rolling to shape according to the American Institute of Steel
Construction’s industry average Environmental Product Declaration
(EPD). The emissions from high-energy processes to produce molten
steel and form shapes are avoided by reusing components directly.
While some companies such as Rheaply, Building Ease, and All for
Reuse have developed material exchange databases for non-struc-
tural salvaged components, North America lacks circular economy
infrastructure and at-scale salvaged material markets. A few North
American municipalities have reuse and landfill diversion legislation,
mainly for non-structural materials or dimensional lumber. This
policy landscape contrasts with Europe’s recent policies and expan-
sion of commercial markets that enable structural component reuse
in London, Belgium, and the Netherlands. The reuse of structural
components is unique in that geometry, material properties, and
structural integrity must be well documented or at least discover-
able, to enable reuse in structural applications due to life-safety
requirements. This adds burden to structural materials that is not
present for non-structural materials.
Boulder Community Hospital
The city-owned Boulder Community Hospital (BCH), a roughly
250,000 square-foot building, was sustainably deconstructed in 2023.
For this building, the goals were to achieve 90% waste diversion,
prioritize reuse, and illustrate the potential for a circular economy
and long-term material stockpile within the city. The project achieved
93.5% landfill diversion of all interior and exterior materials by
The Boulder
Community Hospital
was sustainably
deconstructed in
2023. Shown is the
before (left) and after
(right) deconstruction
of the site. (Credit:
City of Boulder).
Installed salvaged steel at Fire Station 3 is identifiable by the unused bolt holes (credit: Feitel,
KL&A).

11. AUGUST 2024 11
weight (98% of the core and shell). This is understood to be the first
major commercial building to be entirely deconstructed and the
first structural steel stockpile of its kind and scale in North America.
KL&A Engineers & Builders’ Team Carbon was contracted to
develop processes, requirements, and documentation for material
management and administration to facilitate the deconstruction,
stockpiling, and reuse of the steel in BCH. The process was developed
in collaboration with Ameresco Inc. (general contractor), Colorado
Cleanup Corporation (deconstruction contractor), and the City of
Boulder. KL&A was in a unique position to approach this project
because of its combined structural engineering, construction manage-
ment, steel detailing, and embodied carbon expertise. Fundamentally,
it was approached from the perspective of the end-user: new construc-
tion structural engineers.
What dimensional information is needed to implement salvaged
steel? What physical and capacity information is needed for an engi-
neer to incorporate salvaged steel? What legacy information from
the original use is important? When does a new construction project
need this information?
The general process phasing and flow is illustrated above.
As is typical for innovation in design and construction, significant
obstacles were assessing risk, cost, and quantifying uncertainty. Four
key logistical factors enabled the project to advance through this
uncertainty:
1. City of Boulder owned the deconstruction, stockpile, and new
construction.
2. The deconstruction and new construction schedules aligned.
3. Stockpile laydown space was available for roughly 2 years.
4. Pieces of salvaged steel were connected to end-uses prior to
deconstruction.
584 wide-flange and tube members (HSS as they are known today)
were successfully recovered and stockpiled, totaling 161 short tons. At
the time of this writing, one new construction project, Boulder Fire
Station 3, has successfully installed 89 salvaged members, nearly 25%
of the inventory by weight. An additional 298 steel pieces have been
claimed and, in some cases, retrieved by new projects, some owned
by the city. There are 197 remaining pieces available for procurement,
resting at the BCH site, which are intended to be used in the site
redevelopment and other construction projects across the state. The
stockpile is owned by the city and managed by KL&A.
Material Source
BCH was primarily comprised of cast-in-place concrete structural
systems, constructed in 1957 with numerous additions and renovations
through the early 1990s. Two areas were steel systems: Source A and
Source B. Concrete components were conventionally demolished,
however, the material was processed, sorted, crushed, and reused
onsite as basement fill.
Source A represents the 1986 and 1989 additions, totaling 18,000
square-feet, consisting of three levels above grade, utilizing non-
composite steel wide-flange beam and column framing, steel open-web
bar joists, concrete on metal deck floors, and metal deck roof. The
framing and deck were covered entirely in spray-applied fireproofing.
The Source A structural and architectural drawings were available,
which were utilized to create a digital inventory. The timing of the
digital inventory is noteworthy, as this allowed the Fire Station 3
team to select individual pieces before deconstruction and early in
their design process.
Source B represents the 1982 and 1989 single-story additions,
totaling 28,000 square-feet. The structure is one level above grade,
utilizing non-composite steel wide-flange beam and column framing,
HSS columns, and metal roof deck. Like Source A, the framing and
deck were covered entirely in spray-applied fireproofing. Architectural
drawings were available but did not include any structural system,
member, or material information.
All wide-flange and HSS sections were targeted for deconstruction.
The steel bar joists were recycled because the probability of damage
during deconstruction was high due to their light shapes and welded
seat connections, although steel joist reuse has been demonstrated in
projects by KL&A and others. Many steel bar joists were originally
Defining the Saved Embodied
Carbon of the Boulder
Community Hospital Stockpile
The stockpile from the Boulder Community Hospital is estimated to
have saved 167,338 kgCO
2
eq in embodied carbon. This saving
is equivalent to 37 gasoline-powered passenger vehicles driven
for 1 year. Compared to the embodied carbon of typical new
construction (400 kgCO
2
eq/m
2
, 37.2 kgCO
2
eq/ft
2
), this saving is
equivalent to 4,500 square-feet (418 m
2
) of floor area.
The saved embodied carbon is equivalent to the Stage A1
impacts reported in the ASCE’s Fabricated Hot-Rolled Structural
Sections, 2021 industry average EPD and Fabricated Hollow
Structural Sections, 2022 EPD. The estimate does not consider the
deconstruction emissions compared to traditional demolition.
The general process phasing and workflow for the deconstruction, recovery, and reuse of BCH steel (Credit: Feitel, KL&A).

12. STRUCTURE magazine 12
optimized for localized loading conditions and are therefore inappro-
priate for general structural reuse, requiring reverse engineering. Steel
members that have experienced cyclical loading, plastic deformation,
or other unique loading conditions may not be suitable for structural
reuse. Component characteristics and installed conditions affect the
ease and challenges of recovery and reuse. A member may be easy
to recover and lack reuse application. Inversely, a member may be
challenging to recover but have high value.
Deconstruction
KL&A authored a Steel Deconstruction Specification that detailed
cut locations, level of cleanup, and piece-marking requirements. It
defined the resulting condition of the steel pieces which allowed new
construction projects to bid the fabrication scope appropriately. The
purpose of defining cut locations was to balance the ease of decon-
struction with recovering as much of the members’ length as possible.
It was anticipated that 12 inches would be removed from each end
at some point during the process. An average of 27 inches total was
removed from the original length of Source A pieces.
The deconstruction team recovered 30 beams per day. The “flying
time” of the Source A beams was 12 minutes, from removal to setting
on the ground. Source B recovery was much faster, primarily because
it was a single-story structure, and the team was familiar with having
completed Source A. It is estimated that fewer than 30 pieces (5%)
were damaged and therefore unsuitable for structural reuse. These
pieces were either recycled, used for material testing then recycled,
reserved for non-structural applications, or used as stockpile dunnage.
At the time of this writing, the BCH deconstruction costs are still
being analyzed and cannot be reported in detail. The total cost of
deconstruction (interior plus core and shell) was $9.2 million, compared
to an estimated demolition cost of $7.7 million, a $1.5 million (19%)
premium. The floor area of Source A and B was roughly 18% of BCH.
Component Processing
The order of operations varied between the two sources, primarily
due to the availability of structural drawings for Source A and lack
thereof for B. For example, fireproofing was removed from Source
A steel, and each component was piece-marked to match the digital
inventory before deconstruction. However, Source B fireproofing
was removed in situ, further cleaned off while on the ground, then
piece-marked, and then inventoried.
Member cleanup consisted of removing fireproofing and accessory
material (plates, appendages, etc.). 90% of fireproofing, within any
6 square-inches of surface area, was removed onsite. This is not
considered unique to deconstruction versus demolition, as metals
recycling facilities typically do not accept steel with fireproofing, or
they accept it at a lower value because it must be removed eventually.
All accessory material that extended beyond the boundary of the
member’s cross-sectional area was removed onsite, except for material
that extended a significant length along the member, such as welded
deck-edge angle. The purpose of cleanup was to ease handling during
recovery, vertical stacking at the stockpile, transportation, and process-
ing by fabrication equipment which often uses rolling conveyors. A
stockpile endeavor should balance cleanup effort against the intended
end-use, time, cost-sharing, and ease of handling. New projects may
be unconcerned about extraneous material or even decide to highlight
those features as part of their aesthetic and project brand.
A physical and digital inventory was created to document, track,
and identify individual pieces of steel. The digital inventory housed
component characteristics, as well as logistical information like the
specific location in the physical stockpile, if it was to be sampled for
material testing, and claims by new projects. The inventory tracked
total tonnage, embodied carbon savings, and estimated cost compared
to standard new steel.
Measurements and photos were taken onsite, and descriptive infor-
mation was recorded, such as general condition (finish, corrosion),
accessory material and holes (connections, penetrations), observed
damage (excessive bend, missing material), and observed geometry
(camber, sweep, tilt). This was used to develop individual cut sheets,
assign historic AISC Manual of Steel Construction shape categories
(e.g. W14x22), and flag any noteworthy conditions for the end-user.
Material Testing
There is no industry standard or code requirements for testing
and validating salvaged steel for structural reuse in North America,
An excerpt from the Steel Deconstruction Specification: Example of Acceptable Cut
Locations (credit: KL&A).
An excerpt from the Steel Deconstruction Specification gives an example of cleanup
requirements (credit: KL&A).

13. AUGUST 2024 13
although protocols have been developed for other regions. KL&A
developed a testing protocol, based on recommendations from ASCE
41-13: Seismic Evaluation and Retrofit of Existing Buildings and the
Steel Construction Institute’s Structural Steel Reuse: Assessment, Testing
and Design Principles.
Samples were taken and tested to estimate the properties of size
categories within each source rather than from every piece. ASTM
A370 tension testing was performed on 10% of the pieces in each
size category and ASTM A751 chemical analysis testing, to verify
weldability, was performed on 10% of the total quantity of pieces.
The third-party laboratory required 1x8” samples and cost about
$100 per sample. Additional testing may be necessary based on the
source and end-use.
Based on the dates of construction and available documentation, it
was anticipated and validated by testing that the wide-flange members
are equivalent to ASTM A36 and tube members equivalent to ASTM
A500 Gr. B. All the samples confirmed weldability, with some results
recommending preheating procedures.
Reuse in New Construction
The financial feasibility of deconstruction is directly tied to con-
necting an end-use of the recovered material, whether it be specific
or a general resale market opportunity. Understanding the ability
of Fire Station 3 to utilize pieces from BCH was critical to moving
forward with recovery.
The uncertainty of logistics, cost, and risk is a significant barrier
to innovation. The cited motivations of projects that engaged
with the stockpile were sustainability goals (embodied carbon
reduction), appetite for innovation, project brand differentiation,
and material cost savings. It was evident that the reliability of
member sizes, geometry, and material testing results of salvaged
structural components are highly desirable to new projects before
design implementation.
The Fire Station 3 structural design team claimed pieces from the
inventory during Design Development to incorporate into roof
framing over the apparatus bay and mechanical screen framing atop
the roof. The sizes and anticipated strength were incorporated into
the analysis model. The structural Construction Documents noted
in plan the locations for the intended use of the steel. Full Metal Iron
retrieved and transported the pieces from the BCH stockpile to their
fabrication shop. After a final cleaning, the fabrication process was
reported to be seamless and like that of new steel. It was successfully
installed in 2023. There were no reported differences in fabrication
or installation costs and schedules, and the steel was procured at zero
cost to Fire Station 3. This resulted in net cost savings of 0.5% of
the total steel contract because the material savings outweighed the
fabricator’s cost to transport and clean the steel.
In the future, policy requirements and consumer demand will be
strong motivations to consider salvaged structural materials. It is
reasonable to speculate that the use of salvaged steel in new construc-
tion can be cost-competitive, even when considering a resale value.
Conclusion
This project illustrates that at-scale deconstruction and reuse of
structural steel components is possible and financially feasible. The
necessary change in behavior, priorities, and incentives is more chal-
lenging to overcome than the technical and logistical aspects. To
advance structural material recovery and reuse, several topics arise -
policy and incentives, protocol and code development, Environmental
Product Declaration development, collaboration among building
stock and new construction, specialty business opportunities, technol-
ogy opportunities, and design for deconstruction (DfD). Through
concerted efforts, strategic initiatives, collaboration, and reinvention
the construction industry can pave the way for circular economy,
embodied carbon reductions, and environmental stewardship.
Alexis Feitel is the project manager for the Boulder Community Hospital salvaged steel.
She co-founded and leads KL&A Engineers & Builders’ Team Carbon. She is on the
steering committee of ASCE Structural Engineering Institute’s (SEI) Sustainability Committee
and a contributing Circular Economy Working Group member. ([email protected])
Dan Bergsagel leads schlaich bergermann partner’s sustainability brief from their NYC
office and is a visiting scholar at Cornell AAP’s Circular Construction Lab. He chairs the
ASCE Structural Engineering Institute’s (SEI) Sustainability Committee Circular Economy
Working Group. ([email protected])
Wide-flange and HSS pieces rest at the BCH stockpile (credit: Feitel, KL&A).
Full references are included in the online version of the article
at STRUCTUREmag.org.
Circular Economy Working Group
This case study is part of a new database of circular economy projects
published by the ASCE SEI Sustainability Committee’s Circular Economy
Working Group. For more information about the database and for
information on submitting case studies please visit https://se2050.org/
resources-overview/case-studies/.

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16. STRUCTURE magazine 16
Designing New Structures for
Deconstruction to Get a Circular Economy
Developers can see end-of-life profits from deconstruction by considering engineering pre-planning in new
structure builds. By Steven Anastasio, PE
structural SUSTAINABILITY
"B
uilt-to-last” has been an underlying mantra in the field of struc-
tural engineering. When we pen structures onto the boards,
we draw them to be more durable than any of the other building
systems, so we can’t fathom the end of life of the building. We design
with the expectation that the structures will become fixtures on earth
indefinitely, or at least to outlive ourselves.
Because of this, there is less motivation to plan for the back end of
the building life cycle, especially in a developer driven industry, and
when it can seem daunting to even predict the trends 20 years out.
Some trends are apparent right now, though. Buildings are becom-
ing lighter and more efficient, technology and trends are changing
more frequently, and methods of construction, deconstruction, and
reconstruction are improving.
While recycling is a good strategy, it is not the overall goal. The
overall goal is to have a circular economy where materials are reused
for similar items as many times as they can before they are recycled.
The practice of incorporating deconstruction into the lifecycle of a
building has been around for decades, albeit on the fringes because of
the speed and lower cost of the wrecking ball and landfill placement.
Now with sustainability requirements and lower carbon mandates,
along with rising landfill prices, the time for serious consideration of
building end-of-life and recycling has become imperative to consider
early in the construction process. As the Urban Land Institute/PWC’s
2024 Emerging Trends Report recently stated, “Real estate profes-
sionals can no longer ignore the embodied carbon elephant in the
room, and stakeholders are putting on the pressure from all angles
to address the issue.”
In a 600,000 square-foot multi-family high rise of 48 stories which
utilizes cast-in-place concrete, the embodied carbon makes up 38%
of the total carbon in the building with the structure itself making
up 63% of the 38%. So, if you look at the overall operational and
embodied carbon in the entire building—the structure alone makes
up 24%. Traditionally, when the lifecycle of that building expires,
the owner has the option to reallocate for a different purpose, if the
structure and systems make that feasible. If not, the structure will
be demolished, taking with it all of that embodied carbon and send-
ing it to the landfill. This is a huge waste and potentially a missed
opportunity to gain the associated revenues for reusing, recycling, and
reallocating materials. More developers are now exploring strategies
for deconstruction of a building from the onset of the construction
cycle. This early focus allows them to see the potential for reselling
the materials at the terminus of the building, while incorporating
sustainability practices. This has led to active conversations with
architects and engineers about planning for deconstruction.
What Is Deconstruction?
In 2018, the EPA estimated that 600 million tons of Construction &
Demolition (C&D) debris were generated, and the average building
demolition created 155 pounds of waste per square foot of building
area. A 50,000-square-foot building creates 3,875 tons of debris when
it is demolished and carted away.
Currently, the industry is selectively recycling building components.
Terrain Gardens at
Devon Yards in Devon,
Pennsylvania, reused steel
trusses from a University of
Maryland structure built
with bolted connections
for easy disassembly and
then reconnected them in
the new space to form the
framework of their new
venue. (Photo credit: David
Greer.)

17. AUGUST 2024 17
If the debris is elected to be directed to a recycling plant in broken
rubble form—the components are separated and resold either in
the component’s same use or downgraded for other uses. This recy-
cling process is laborious and mechanically intensive. For instance,
concrete is crushed down, and an Eddie current separator sorts the
metals. Wooden material and foams are separated in a water bath. It
is estimated that three-quarters of construction waste can be recycled;
however, about one-third is recovered.
Recycling construction materials is difficult. That's why deconstruction
is so important. The structural materials take up a huge portion of the
landfill, often making it more impactful. The architectural products
are certainly more complex to deal with, but when everything goes
into a landfill and isn't considered for recycling, the size matters most.
To bridge this gap, it is on the design profes-
sionals to specify and design buildings that
facilitate reuse and recycling after demolition.
Demolition is complete disposal, whereas
the EPA Resource Conservation and
Recovery Act (RCRA) defines deconstruc-
tion as “the selective disassembly of buildings
to facilitate the reuse or recycling of valuable
materials.” Focused on salvage, this method
takes whole, or partial, components of a
structure and carefully disconnects them.
For example, a connection that can be
unscrewed is much easier than a welded one
which requires more invasive disconnection
measures that could compromise reuse. It’s
essentially going in the reverse order of build-
ing a structure. You start first by removing
finishes and fixtures and then progress to
the structural elements, like electrical and
plumbing infrastructure, and then to the
core structural elements such as beams and
trusses. Reuseable/recyclable elements are
then resold or stored for reuse.
Good candidates for deconstruction are
buildings with short life cycles, or re-location
cycles, such as those for retail, health-clinics
and task-oriented buildings (storage, show-
room, military, classrooms and agriculture).
By assessing the lifespan of the building—is it
more permanent or temporary—a developer
can get an idea of the kind of construction
that lends itself to deconstructability. For
a use that will change frequently (yearly),
a highly temporary construction—like a
shipping container—works well and pro-
vides flexibility for new uses. A use that will
be maintained for one to five years can use
modular box construction and panelization
of components for easy disassembly. For a
building that will have a low turnover fre-
quency—five to ten years—conventional and
durable materials can be bolted together and
disassembled in part, or as a whole.
A fine example of deconstruction reuse can
be found at the Terrain Gardens at Devon
Yards in Devon, Pennsylvania. Terrain is a
garden center and restaurant that has incor-
porated indoor/outdoor event space into
their operations. Focused on creating an immersive natural experience
for their retail space and events, Terrain reused steel trusses from a
University of Maryland structure that had used bolted connections
for easy disassembly and then reconnected them in the new space to
form the framework of their new venue. The result was a one-of-a-
kind, sustainable setting that supported the values of the organization.
Engineering Considerations in
Deconstructability
To effectively plan for deconstruction from an engineering perspec-
tive, the original building concept needs to include:
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18. STRUCTURE magazine 18
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STRUCTUREmag.org
Steven Anastasio, PE, is the Director of Structures
for Bala Consulting Engineers, Inc. Anastasio
concentrates on industrial and residential markets,
with a keen focus on structural dynamics, blast
engineering, and earthquake engineering.
Full references are included in
the online version of the article at
STRUCTUREmag.org.
• Materials assessment—Implementing durable and non-toxic
materials
• Easily separable—Use of mechanical fasteners instead of adhe-
sives and glue
• Simplicity—Simple components that have limited material
types and sizes
• Limited components—Small numbers of large components
• Clear plans—Labeling and providing diagrams as a roadmap
for future removal
• Transparency—Systems need to be visible and identifiable, not
hidden behind walls
• Regularity—Similar and repeatable systems throughout the
building
• Disassembly safety—Worker safety during deconstruction.
Assessing a Building for Deconstruction
Architects and engineers play a key role in guiding developers
through a property assessment for deconstructability. The following
questions provide an outline for working with building owners to
decide deconstruction pros and cons for a property.
Why are you considering deconstructability? If your business’
mission is focused toward sustainability, then it’s clear that decon-
structability is a good avenue to consider on every project. If it’s not so
clear cut, taking the time to find a building application where shorter,
modular building lifecycles lends itself to
reuse/recycling of materials may serve the
dual purpose of making a profit at the end
of building lifecycle while shining a positive
sustainable light on the developer.
What is the anticipated end use of
the building (including sub-lifespans)?
The longer the anticipated lifespan of the
building the more difficult it becomes to
anticipate the long-term trends and there-
fore, uses and value of the construction
materials. The shorter life buildings have
end of life uses that can be predicted more
easily and with more tangible markets and
buyers for the building components.
Who is on the back end using the build-
ing or materials, and who is deconstructing
it? Likely, the same contractor who builds
a structure will not be the same one who
deconstructs it. In that circumstance, sim-
plicity of design and connection is incredibly
important to the successful deconstruction
and materials in the future. Additionally, is
there already a market for recycling the reuse
of materials that are being used? If there is,
there’s a better opportunity for projecting
values in the future.
These are just some of the questions
that should be considered when choos-
ing whether to pursue a deconstruction
strategy on a new build. Pre-planning
with a qualified, experienced deconstruc-
tion engineer will help ensure a smooth
structure transition at end of life and the
successful capture of associated revenues
from materials reuse/resale.

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20. STRUCTURE magazine 20
New Design Tools Available for CLT
The tools enable engineers to design CLT per U.S. codes quickly and accurately for common applications.
By Matt Kantner, PE, SE
structural DESIGN
C
ross-laminated timber (CLT) is an engineered wood product
that is growing quickly in popularity both in the United States
and abroad. It is just one product in a suite of products and, in fact,
an entire method of construction that is known as mass timber. A
patent for CLT was first issued on August 21, 1923, to Frank Walsh
and Robert Watts of Tacoma, Washington (Fig. 1). Like many great
innovations, the world was not ready for this game-changing prod-
uct at the time, and it largely went forgotten for decades. Then, in
the 1990s, Austrian engineer Gerhard Schickhofer wrote his PhD
thesis on CLT and went on to develop CLT as a commercially viable
product with government approvals first granted in 1998. CLT grew
in popularity in Europe in the early 2000s and has since exploded
into a globally manufactured and utilized product.
Why CLT?
CLT is growing in popularity for a variety of reasons. For one, when
CLT lamstock is harvested from sustainably managed forests, it has
serious green credentials. Replacing more carbon-intensive materials
with CLT can drastically reduce a building’s embodied carbon, espe-
cially when taking biogenic carbon into account. Organizations such as
the American Society of Civil Engineers, via its SE 2050 Commitment
Program, recognize structural engineers’ outsized role in lowering
embodied carbon in buildings; low-carbon materials such as CLT
have a significant role to play. Building occupants love exposed CLT
due to its warmth and its biophilic properties. (Biophilia is our innate
desire to be surrounded by nature and natural materials.) Architects
love it for the warm and beautiful spaces it can create. Builders love
it because panels are prefabricated and get erected quickly and easily
on-site. CLT has inherent two-way spanning
capabilities that can be used for perimeter
cantilevers or even point-supported systems.
Cross laminations make CLT dimensionally
stable in both in-plane directions and allow
it to function as a diaphragm.
CLT Today
Today, many CLT manufacturing facilities
are located all over the world. Six facilities
in the United States are certified to sell CLT
as a structural building product with more
planned, and a growing number of inter-
national suppliers in Canada, Europe, and
South America are gaining U.S. approvals
(Fig. 2). CLT factories are busy… according
to Woodworks, as of March 2024, 2,115
mass timber projects are built, in construc-
tion, or in design across the United States
since they began tracking in 2013; 1,197 of these include CLT. Prior
to 2013, either of these numbers would have likely been in the single
digits. The 2021 International Building Code has helped usher in a new
era of tall, mass timber buildings by allowing mass timber buildings
up to 18 stories. But mass timber and CLT are equally at home in
single-family homes. CLT is also commonly used in office buildings
(Fig. 3), multifamily residential buildings of all sizes, schools, fire
halls, higher education buildings, and more.
Design of CLT in the United States
Design for Strength
Being an engineered wood product, the
design of CLT in the United States is gov-
erned by the American Wood Council’s
(AWC) National Design Specification for Wood
Construction (NDS). CLT first appeared in
the NDS in the 2015 Edition in Chapter 10.
CLT also made its first appearance in AWC’s
Special Design Provisions for Wind and Seismic
(SDPWS) standard in its 2021 edition (see
STRUCTURE July 2021 article) for use as
shear walls and diaphragms.
Reference CLT design values are a bit dif-
ferent than for other wood products—this
is due to the unique properties of CLT that
are inherent because of the transverse layers.
For uniform orthotropic materials like sawn
lumber or glulam, an engineer simply divides
the bending moment by the section modulus
(i.e., M/S) to calculate the bending stress and
Fig. 1. Original patent for cross-laminated timber (though not
known by that name at the time) issued in 1923.
Fig. 2. CLT Manufacturing at Smartlam’s Dothan, Alabama facility.

21. AUGUST 2024 21
divides the axial force by the cross-sectional area to find axial stresses
(i.e., P/A). CLT, however, is a composite material with layers that
are oriented perpendicular to the direction being evaluated, so this
simple calculation is not directly applicable. The design of CLT per
the NDS takes these unique properties into account in Table 10.3.1.
Some key properties from that table include:
• F
b
(S
eff
) for bending. Manufacturers calculate this allowable
bending capacity for the CLT layup using the shear analogy
method as prescribed in ANSI/APA PRG 320: Standard for
Performance-Rated Cross-Laminated Timber, 2019 Appendix
X3 for both the minor and major direction of their panels.
These values, which are known as F
b
(S
eff
), are published in CLT
product code reports.
• (EI)
app
for out-of-plane stiffness. This is where CLT gets really
fun. In most materials and situations, engineers can reason-
ably ignore the impacts of shear deformation (or take them
into account with rough approximations). This is not the case
in CLT. Due to the influence of the transverse layers, shear
deformation in CLT is significant even at high span-to-depth
ratios. A term known as (EI)
eff,
which considers flexural stiffness
only, is calculated using the shear analogy method per PRG 320
Appendix X3. Similarly, (GA)
eff
, the effective out-of-plane shear
stiffness, is calculated. Both of these values are published in
manufacturer code reports. (EI)
app
is an apparent out-of-plane
stiffness that takes both the flexural stiffness, (EI)
eff
, and shear
stiffness, (GA)
eff
, into account. (EI)
app
can be calculated per
NDS 2018 equation 10.4.1 for a given span length, loading
type, and end fixity condition.
• F
t
(A
parallel
) and F
c
(A
parallel
) for axial loading (tension and com-
pression respectively). A
parallel
represents the cross-sectional area
of plies parallel to the direction being considered. Transverse
plies have a negligible impact on the axial capacity of CLT as
wood is far weaker and less stiff perpendicular to the grain, plus
most North American CLT is not edge-glued.
• F
s
(Ib/Q)
eff
for rolling shear capacity. If you are not familiar
with rolling shear, the name is quite intuitive. Imagine wood as
a bundle of straws. For sawn lumber or glulam, parallel-to-grain
shear governs the shear capacity of a section. Parallel to grain
shear can be imagined by taking some of your straws and sliding
them in a direction along their primary axis. Rolling shear is
when you take some of the straws and slide them perpendicular
to their primary axis. Due to the transverse layers in CLT, roll-
ing shear is developed from out-of-plane loading. Also, since
rolling shear allowable stresses are one-third that of allowable
parallel-to-grain shear stresses, rolling shear capacity governs the
out-of-plane shear capacity of CLT. PRG 320 2019 Appendix
X3 provides equations for determining rolling shear capacity,
and in practice, manufacturer code reports simply list a value
V
s
, which can be used directly as an allowable shear strength
per one-foot width of the panel.
Fire Design
CLT is often used in building types that require structural elements
to have fire-resistance ratings of one or two hours. Due to its inherent
beauty and biophilic properties, it is desirable to leave CLT exposed
visually, which also leaves it exposed to fire (Figure 4). Design provi-
sions for CLT exposed to fire exist in the 2018 NDS Chapter 16 as
well as in the recently published Fire Design Specification for Wood
Construction (FDS) by the AWC, 2024. Technical Report No. 10:
Calculating the Fire Resistance of Wood Members and Assemblies (TR-
10) by the AWC is another good reference since it contains worked
example problems.
At a high level, designing timber elements for fire is relatively
simple—wood chars in a fire at a predictable non-linear rate. For
a given fire duration, an engineer can calculate how much wood is
considered ineffective as it heats up and turns to char. The remain-
ing cross-section is evaluated for strength. Only imposed gravity
loads are considered, and the reference ASD strengths for bending,
shear, etc., are multiplied by an adjustment factor, which effectively
makes them ultimate strength
values. Things get more compli-
cated at connections. For a brief
primer on this, see the May 2023
STRUCTURE Magazine article,
“Fire Protection of Mass Timber
Connections Based on the 2022
Fire Design Specification.”
Vibrations
When it comes to designing for
vibrations, a couple of factors
can create challenges for CLT
floors. First, CLT has lower stiff-
ness than an equivalent thickness
of a concrete slab. Second, CLT
has a great strength-to-weight
ratio; the primary downside of
this is that CLT floors have less
modal mass. It also means that
a CLT floor has lower overall
loads compared to a concrete
slab… this is good for strength
design, of course, but makes
it more likely that vibration
Fig. 3. This mass timber office building is built with CLT floors in California. Michael Green Architecture and SERA, EQUILIBRIUM as SEOR.
Photo credit: George Baker.

22. STRUCTURE magazine 22
Matt Kantner, PE, SE, is an Associate Principal at EQUILIBRIUM, where he leads the
company’s U.S.-based team from their office in Atlanta. Like his colleagues, he designs
in all materials but is especially passionate about mass timber and sustainability-focused
design. Kantner is a member of the SEI’s SE 2050 Committee and the American Wood
Council's Wood Design Standards Committee. ([email protected])
considerations can govern the design. As a seasoned mass timber
engineer once told me, a concrete slab’s primary job is holding itself
up. Consider a typical residential floor; the ratio of self-weight to
all superimposed loads is roughly 1.5 for a typical post-tensioned
concrete flat plate floor and roughly 0.15-0.25 for a 5-ply CLT floor.
Vibrations due to human activity are a serviceability criterion that
is not addressed directly in the building code. The U.S. Mass Timber
Floor Vibration Design Guide by Woodworks, published in 2023,
is a tremendous resource for the vibration design of CLT floors. It
includes some simplified provisions for CLT panels on rigid supports
and provides calculation methods for floor plates supported on flexible
(e.g., beams) framing as well.
CLT Design Tools Available
Two new CLT design tools enable engineers to design CLT in accordance
with U.S. codes quickly and accurately for many common applications.
These tools are wrapped up into a single Excel workbook and are available
for free at https://eqcanada.com/design-resources/. Within the workbook,
one tab performs calculations for floor/roof panels: cold strength, fire
strength, deflections, and vibrations are all checked (Fig. 5). The other tab
performs calculations for CLT walls loaded axially, including provisions
for eccentric loading, out-of-plane wind loading, and P-delta effects. Cold
strength and fire strength are checked.
The CLT Design Tools allow users to input any symmetric CLT layup
from three to nine plies. While this can be done manually with ease,
it is even more efficient to select layups from the built-in database.
The layups are called up directly on the calculation sheet from a layup
database that exists on a separate tab and includes every commercially
available PRG 320 certified layup in the U.S. market at the time of
publication. EQUILIBRIUM is committed to maintaining this layup
database and making any other critical updates to the tools for the next
two years and perhaps beyond pending additional funding.
Less refined versions of these tools have been used by EQUILIBRIUM
engineers for years to design CLT on our projects, including some of
the projects shown in the images within this article. The CLT design
tools were officially launched on August 29, 2023. The first update was
made on February 29, 2024. To date, the tools have been downloaded
over 1,100 times. In a recent user survey, over 70% of respondents
ranked the tool's Floor/Roof designer as the best tool they have used
for design of CLT floors and roofs.
The development, release, and promotion of these new tools was
funded by the U.S. Forest Service by way of a Wood Innovation Grant.
Additional funding was received from the Softwood Lumber Board.
Holmes Structures performed a peer review. Early versions of the tool
were originated at Katerra.
Executive Summary
Major DirMinor Dir
F
b
(S
eff
) (ft-lbs/ft)5,250 2,675
V
s
(lbs/ft)3,025 1,820
El
eff
(10
6
lb-in
2
/ft)420 109
GA
eff
(10
6
lbs)1.2 1.2
Overallok ok
Strength0.65 0.20
Deflection0.24 0.09
Vibration0.78 0.00
Fire Strength0.53 0.45
Fig. 5. Within the design tool workbook, one tab performs calculations for floor/roof panels.
Fig. 4. The Wood Innovation and Design Centre. Michael Green Architecture,
EQUILIBRIUM as SEOR. Photo credit: Ema Peter.
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24. STRUCTURE magazine 24
Equilibrium Without Statics
The Modern Müller-Breslau Method is a geometric
way to establish equilibrium in 2D and 3D structures.
By Edmond Saliklis, Ph.D, PE
structural DESIGN
T
he Modern Müller-Breslau (MMB) Method is a new, purely
geometric means of establishing equilibrium in two-dimensional
and three-dimensional structures. It builds off the work by Heinrich
Müller-Breslau (1851–1925), which is well known by civil engineers
around the world as the Influence Line Method.
The impetus of creating the new MMB theory was driven by the
author’s experience teaching many architecture and engineering
students at California Polytechnic State University (Cal Poly), while
trying to address the curious phenomenon of a growing gap between
design students’ knowledge of form creation, and their limited under-
standing of how load flows through the forms they create. The MMB
Method demonstrates visually, with no statics at all, how load flows
to a support or how an internal force or moment equilibrates external
loads. While it can be drawn by hand, even on the proverbial “napkin
sketch,” the method lends itself best to precise simple line drawings
done parametrically on a computer.
Several examples of the new MMB method will be shown in this
article, along with a brief review of the classic Müller-Breslau (MB)
Method.
In the classic Müller-Breslau (MB) Method, to find an Unknown
reaction or internal force or moment, Heinrich Müller-Breslau first
removed the Unknown, be it an external or internal force or moment
equilibrator, then he “perturbed” the structure a unit displacement or
rotation amount Δ in the assumed direction, or sense, of the Unknown.
The MB and the MMB Methods agree perfectly for any scale of Δ as
shown in Figures 1, 2, and 3. In Figure 1, a simply supported beam
contains point loads at each of the free cantilever tips. To seek either
Unknown Reaction, such as the Right Reaction (RR in the classic
MB Method), the RR is removed and a geometric perturbation of
1 unit is applied vertically, because the reaction is vertical. Since the
perturbation is purely vertical, the entire beam stretches, i.e. it elon-
gates. This is known as the “Influence Line” for the Right Reaction.
In Figure 2 for the MB method, the geometric displacement known
as the perturbation is 1 unit and the “loft” or the movement of each
load is -0.3 and 1.1 for F1 and F2 respectively. In Figure 3, the MMB
Method does not stretch the beam. Rather, it respects all boundary
conditions after the perturbation is applied. While the perturbation
Δ is still measured in the direction of the Unknown, the path of the
entire perturbed structure is circular, as shown in Figure 3. Notice
in Figure 3 that the loft of each load is measured solely in the direc-
tion of the load. Both methods agree with theory, and the result is
not earth-shattering, so why go through the trouble of drawing the
perturbed shape without stretching the beam? The answer arises with
lateral loads.
Consider now the slanted, simply supported beam shown in Figure
4. To seek the Unknown Right Reaction RR using the classic MB
Method, the “loft” or movement of the applied load is zero in the
perturbed configuration, regardless of the size of Δ, because the beam
stretches. This would imply that the Right Reaction RR is zero, which
is incorrect. If there is no horizontal movement of the external load,
Fig. 1. A simple beam with two known external forces and two
unknown vertical reactions.
Fig. 2. Finding the reaction on a simple beam via the MB.
Fig. 3. Finding the reaction on a simple beam via the MMB.
Fig. 4. A simple beam with a lateral load.

25. AUGUST 2024 25
Fig. 5. Find the reaction induced by a lateral load via the MB.
Fig. 6. The perturbed MMB beam with a lateral load and a large Δ.
Fig. 7. The perturbed MMB beam with lateral load and a small Δ.
Fig. 8. A three-hinged arch subjected to an asymmetric live load.
then there is no work done by it, so there would be a zero reaction.
But, there is indeed a vertical reaction on the slanted beam, induced
by the horizontal load.
Using the MMB Method, one simple work equation can be applied
to any structural problem. Work is force multiplied by a distance.
The distance is either Δ for an external reaction, or it is a Loft for an
applied external force.
Equation 1 Unknown ∙∆+ ∑F
i
∙ Loft
i
=0
Figure 6 shows the solution to this problem for a large perturbation
Δ, and Figure 7 shows the solution approaching the theoretical value as
Δ gets small. The circular path is evident, yet the perturbation Δ of the
Unknown and the Loft of any load is only in direction of those loads.
Consider now, a slightly more complicated structure, a three-
hinged arch subjected to a partial live load projected uniformly
along a horizontal line, as shown in Figure 8. Suppose the Unknown
moment in the left “elbow” shown in Cartesian Coordinates at (2,5)
is sought. Most students would balk at this problem if asked to solve
it algebraically. Yet, with the MMB Method, the problem requires
as minimal effort as the previous examples show. The Unknown,
which here is the moment in the elbow, is removed. That juncture
is perturbed some amount Δ. All pieces must remain straight, and
all other boundary conditions must be respected. Then, the Loft
of the loads is simply measured. One necessary rule is to break a
distributed load into separate parts if the load passes over a kink
in the perturbed structure. Figure 9 shows the perturbed structure
for a large Δ.
Reducing Δ by an order of magnitude shows that the solution
rapidly approaches theory. This is demonstrated in Figure 10. Notice
that the right elbow does not get distorted in the perturbed con-
figuration. All boundary conditions are respected, and only one
violation occurs at the Δ for the Unknown being sought. The first
part of the distributed live load passes through Ld1 in the original
configuration and through Ld1’ in the perturbed configuration. The
second part of the distributed live load passes through Ld2 in the
original configuration and through Ld2’ in the perturbed configu-
ration. Since those loads are vertical, the lofts associated with each
load are vertical. If the sign of the load vector agrees with the sign
of the loft, that work, or product of two terms, is positive. If the
signs disagree, that product of two terms is negative. The Unknown
internal moment is a double negative, so Equation 1 can be used as-is.
Finally, Figure 11 shows a problem that many engineering stu-
dents would most likely answer incorrectly if attempting to solve
it algebraically via statics. A frame is pinned at the lower left end,
roller supported at the lower right end, hinged at the Crown con-
necting the two frame members, and a tensile tie cable that begins
at a distance of 1/3 of each of the lengths of the frame members,
starting from the base supports. The load is a dead load, uniformly
applied along the length of each frame member and downward. The
Unknown tensile force in the cable is sought.
The power and the efficacy of the MMB Method is shown in this
example because once again, Equation 1 finds the solution. Since the
Unknown force in the tensile tie is sought, it must be perturbed some

26. STRUCTURE magazine 26
Fig. 9. The solution for moment in left elbow, with a large Δ, and
a large error.
Fig. 10. The solution for moment in left elbow, with a small Δ; the answer
approaches theory.
Fig. 11. A three-hinged frame on uneven supports, with tensile tie.
Fig. 12. The tensile tie force solution, with a large Δ and a large error.
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27. AUGUST 2024 27
Edmond Saliklis, Ph.D, PE, is Professor of Architectural Engineering, California Polytechnic
State University, San Luis Obispo, CA. He teaches structural engineering courses to
architectural engineering students and to architecture students using geometric methods.
Fig. 13. The tensile tie force solution, with a small Δ and a small error.
amount Δ in the direction of the tie itself. The perturbation Δ here
means that the tensile tie gets longer. Yet all other boundary conditions
must be respected, and the frame members do not stretch. Students
delight in solving the purely geometric puzzle of understanding the
perturbed shape. The free children’s software GeoGebra, which is
meant to teach children Geometry and Algebra, is ideally suited for
such problems and available in many languages. The lofts are imme-
diately found using GeoGebra as a easy to find measurement in the
Geometry window of the program.
Figure 12 shows the solution for a large Δ, and Figure 13 shows the
solution approaching theory for a small Δ. Δ is the difference in lengths
of the perturbed tensile tie and the original tensile tie. The lofts are
always in the direction of the load. The only difference is that for an
internal force, we slightly modify Equation 1 to account for the fact
that any Δ is always opposed by the internal force, i.e. that product is
always negative. If we stretch the cable, the internal force pulls back
in the opposite direction of the Δ. The same phenomenon happens
with internal moment, but those details are not shown here, and
Equation 1 can solve for an internal moment because the Unknown
product has a double negative.
Equation 2 Unknown ∙∆+ ∑F
i
∙ Loft
i
= 0
Many other types of problems can be quickly solved using this
method, including trusses and three dimensional simple spatial struc-
tures. In each case for any statically determinate problem, the MMB
Method approaches theoretical values as Δ gets small. The method
also can be applied to indeterminate problems, albeit in an approxi-
mate manner.
The method’s power arises from the fact that it is purely geometrical.
No algebraic or graphic statics are used. The perturbed shapes clearly
demonstrate that some loads have significant flow to a reaction,
whereas other loads have negligible flow.
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28. STRUCTURE magazine 28
structural INFLUENCERS
Duane Miller
Duane K. Miller, PE, ScD, is a recognized authority on the
design and performance of welded connections. Elected
to the National Academy of Engineering in 2024, Miller is
a past chair of the American Welding Society (AWS) D1
Structural Welding Code Committee and a past co-chair of
the AASHTO-AWS D1.5 Bridge Welding Code Committee.
STRUCTURE: What led you to study welding engineering?
Miller: I had decided to attend LeTourneau University in
Texas before I settled on Welding Engineering (WE), although
I had heard of its WE program. Originally, I was a Mechanical
Engineering major. But there was an excitement and uniqueness
associated with their Welding Engineering program, so I took a
WE elective as a freshman. I liked the tangible aspects of welding
engineering, and I was always inclined toward hands-on activi-
ties. WE graduates had a 100% job placement record, and they
were getting the top offers in terms of pay. Ultimately, I chose to
double-major in WE and ME.
STRUCTURE: How did Omer Blodgett, the author of "Design
of Welded Structures," influence you as an engineer?
Miller: Mr. Blodgett is one of the five most influential individuals in
my life. He taught me how to approach a problem, look beyond first
impressions (which are often wrong), and identify the fundamental
causative factors. In his heart, he was a mathematician, so he always
looked for a mathematical explanation. He often said, “math doesn’t
lie.” He loved welding (he first welded when he was ten) and wanted
others to know how to use it properly. He viewed knowledge as an
inheritance, something to be held and protected for a time, and some-
thing we were to pass along to others, hopefully in a better condition
than what we received.
STRUCTURE: What do you think is the biggest misconception
engineers have about welded connections?
Miller: Many engineers view welding as just another way of joining
materials, but it is far more than that: welding is a method of design.
Welding revolutionized the design of bridge girders as compared
to the riveted alternative. Gone are all the angles and lap plates
associated with making riveted connections. Welded connections
are lightweight, highly efficient, and dependable when designed,
detailed, and constructed properly. Welding is far more than an
alternative to rivets and bolts.
STRUCTURE: What would you consider some of the major
surprises that you have found in your research/development of
welds/welding design?
Miller: Early in my undergraduate studies, I learned that fatigue was
the number one cause of the failure of welded connections. Yet, I was
not taught “why” (or, at least I didn’t listen to that part of the lecture).
As I studied the work of others, I learned the “why” behind fatigue
failures. Additionally, I learned how to design welded connections to
overcome fatigue problems. Then, there was the issue of fracture. I
learned that constraint and notches are the key contributors to fracture.
Eventually, I came to realize that problems associated with welded
connections were usually associated with cyclic or impact loading,
notches, and constraint. What was typically presented as a “welding
problem” was almost always a design-related problem.
STRUCTURE: Of all the initiatives you’ve been involved in,
what has been the most rewarding?
Miller: The Northridge Earthquake in 1994 was a career-changing
event. I was named Chair of the AWS Presidential Task Group,
a member on the Project Oversight Committee for the Federal
Emergency Management Agency-sponsored SAC Steel Project,
and the first Chair of the AWS D1.8 Seismic Welding Committee.
All of these activities “moved the needle” and changed engineering
practices. On a personal level, I was able to associate with and learn
from some of the most brilliant engineers in practice. It was an
honor to associate with these people, most of whom have become
personal friends of mine.
STRUCTURE: Who inspires you?
Miller: I have had the good fortune to associate with many amaz-
ing people. At the top of my list is my late father who instilled in
me a belief that I could do anything I set my heart and mind to
do. My LeTourneau professor Dr. David Hartman inspired me to
pursue graduate school and learn about Fracture Mechanics. Dr. John
Barsom is “Mr. Fracture Mechanics” to me, having written the book
that I studied in graduate school. Dr. Barsom is an amazing person
who has encouraged me on a professional and personal level. Dr.
Barsom’s best advice to me: “Duane, don’t neglect your family.” Mr.
Donald Hastings hired me at Lincoln Electric; he was an inspiring
leader who eventually became CEO. He convinced me to join the
company and to go into sales for a while; both were wonderful sug-
gestions. I’ve already mentioned Mr. Blodgett. These five individuals
all changed the trajectory of my life in positive ways.
STRUCTURE: What do you think you will be remembered for in
terms of your personal legacy, and/or what are you most proud of?

29. AUGUST 2024 29
Miller: I hope I’ll be remembered as a good husband, a good
father, a good grandfather, and one who was a consistent follower
of Jesus Christ.
STRUCTURE: We don’t often see engineers featured on TV.
Can you speak about your experience on the History Channel
and Discovery Channel?
Miller: The directors of these programs conceptualized shows
that featured welding, so it was natural for them to contact Lincoln
Electric for information. We opened our doors and allowed them to
film the welding processes and interview our people. I was identified
as someone who could answer some of their questions. The directors
and I talked with each other for an hour or so, all while being filmed.
I was surprised to see what they chose to keep and cut. Some of my
best replies ended up on the cutting room floor!
STRUCTURE: As a speaker or a professor, how would you
describe your style of teaching?
Miller: I start with where my audience is. What do they know?
What do they need to learn? What steps are needed to get them
from point A to point B? Mr. Blodgett was passionate about making
sure our customers and audiences learned the lessons we taught. He
had no desire to impress others with his knowledge; he wanted to
transfer his knowledge to others. I’ve tried to emulate that approach
in my teaching. I also try to make learning fun.
STRUCTURE: What are the most important attributes of
being a good engineer?
Miller: The most important attribute is integrity. An
engineer must deal with the facts in an unbiased and objec-
tive manner. The second most important attribute is to
maintain a focus on the advancement and betterment of
human welfare. Engineering is a noble profession; every
engineer must maintain the highest standards of profes-
sional conduct.
STRUCTURE: What advice would you give to young
engineers?
Miller: Be honest. Keep learning. Never guess. Read
Petroski. Write papers. Make presentations. Join technical
committees and become an active contributor. Seek to learn
the “why” behind the “what” and “how.” Find a mentor.
Be a mentor. Become a specialist (an expert in a narrow
field of engineering). Realize that there is more than one
solution to a problem. Be professional. Give 20% more
than anyone else in the office.
STRUCTURE: What do you think is the biggest chal-
lenge facing our profession in the next ten years?
Miller: Artificial Intelligence (AI) will transform many
aspects of our life, including engineering. I’m concerned about the
potential effect of AI on engineering. In some cases, AI will give
us answers that are just plain wrong; hopefully, we’ll realize when
that happens. In other cases, AI will give us the correct answer, but
we’ll not know the “why” behind the answer. When this happens,
engineering progress will be hampered. We must understand the
physics behind our engineering principles and equations. We must
know more than just the answer, particularly as we push the limits
with our designs. AI will help us with what exists but will mislead
us when it comes to developing what does not exist. AI will not
replace thinking engineers.
STRUCTURE: What do you think is the biggest opportunity
moving forward in this industry or something exciting and new
that you’re looking forward to?
Miller: Additive Manufacturing (AM) (sometimes called 3-D
printing) holds great promise in the area of structural engineer-
ing, particularly in the realm of connections. Traditional steel
members, whether they be rolled shapes or hollow structural
shapes (HSS) have been joined with nodes made with steel
castings. Where castings are impractical due to limited volume,
AM parts can be made instead. The technology exists today
and is being used in other industries. I look forward to the first
building and the first bridge that will incorporate additively
manufactured components. ■
Miller (far left) and his family gather at a Cleveland Guardians baseball
game
Miller (left) trains welders for ReIGNITE Hope.

30. STRUCTURE magazine 30BIOMIMICRY AT THE LEAF

31. AUGUST 2024 31
he Leaf at Canada’s Diversity Gardens in Assiniboine Park in Winnipeg,
Manitoba, has been described as a “horticultural sanctuary for the 21st
century.” Interior biomes celebrate the flora of Mediterranean and tropi-
cal climate zones, and a butterfly garden allows guests to interact with a
wide range of butterflies. The principals of biophilia, which is the human
tendency to interact or be closely associated with other forms of life in
nature, inform every aspect of the design of the building.
The structure of the building, which must be non-combustible due to its
public program and scale, takes advantage of biomimicry—the emulation
of elements of nature in design. Biomimicry can take two forms. Formal
biomimicry emulates natural forms, while functional biomimicry emulates natural
systems to solve functional problems. The Leaf employs functional biomimicry with
resulting biomimetic forms using state-of-the-art technologies.
The Roof
ETFE Pillows—The Spirals
The most striking formal element of the Leaf is the sweeping spiral cable net of the
roof. The roof supports inflated pillows of ethylene tetrafluoroethylene (ETFE),
a fluorine-based plastic with high corrosion resistance and strength over a wide
temperature range. Technologically, the pillows follow directly from Frei Otto’s
soap bubble experiments in the early 1960s.
ETFE was chosen for the project for its high light transmissibility, particularly the
plant-critical UV light, and economy, particularly when compared to glass. While
ETFE is not “vision clear,” it diffuses light slightly in its passage through the mem-
brane, so shapes and forms are easily distinguishable, and it reflects or absorbs only
around 5% of the light. This is a critical factor when designing an indoor botanical
garden at a latitude of 50° where the shortest day is barely more than 8 hours.
The functional objective of the roof was to minimize shading. A cable net was
considered ideal because, with a light transmissibility of 95% in the membrane, most
of the shading is structural shading. Cables, by virtue of their high strength (fully
locked strand cable has a breaking strength in excess of 180 ksi) can be dimensionally
small when the form allows. ETFE as a system can accommodate large movements
without a reduction in performance. A large deformation structural system allows
each element to be fully utilized for strength (demand/capacity ratio close to 1)
minimizing its size.
ETFE, the foil, is extremely economical and the surface area of the foil is a minor
contributor to the cost of the system. Working with Vector Foiltec in the early
stages of the project, the design team learned that the cost of the system is largely
in the extrusions, which form the boundaries, and in the labor to install them.
The key to an economical system, as well as the key to minimizing shading, is to
minimize the boundary to surface ratio. This constraint suggested two possibilities:
long parallel pillows and large discrete rhomboid or hexagonal “tiles” (similar
BIOMIMICRY AT THE LEAF
The structural systems and details of “The Leaf" at Canada’s Diversity Gardens,
Assiniboine Park in Winnipeg, reflect biophilic design.
By David Bowick, P.Eng.
The striking spiral cable net
of The Leaf's roof consists of
inflated pillows of ethylene
tetrafluoroethylene (ETFE),
which is a plastic with
high corrosion resistance
and strength over a
wide temperature range.
ETFE also has high light
transmissibility which is
crucial for the plants within
the building—especially in
a city with short days. ETFE
only reflects or absorbs
around 5% of light.

32. STRUCTURE magazine 32
to Grimshaw’s Eden Project in
the UK).
ETFE pillows are leaky and
require a constant supply of air to
remain inflated. A tiling of discrete
pillows would require a system of
ducts to bring air to the pillows,
adding cost and shading to the
system.
The planning of this building
placed the mechanical equip-
ment, including the inflation
fans, in the central core. To
avoid air distribution ducts,
each pillow must terminate at
the core. Conventional planning
would orient the pillows radi-
ally, requiring over 100 pillows,
tapering from a minimum width
of around 1 foot to a maximum
around 10 feet at the perimeter
(the approximate maximum span
of the ETFE cushion in a one-
way system). This would result in
almost 50% shading near the core.
Reducing the number of pillows
to limit shading would require
two or more subdivisions of the
pillows over their length—the
strategy employed at Foster’s Khan
Shatyr Entertainment Center in
Kazakhstan. This solution would
require air distribution ducts to
bring air from the core to the sub-
divided pillows.
The solution chosen for this
structure borrows from the mol-
lusc. The mollusc builds its shell
by laying down a single continu-
ous strip of calcium carbonate in
a spiral form to create an ever-
expanding cone of constant
proportion. These cones might
be acute and wound like a snail
or flat like a clam. In this project,
rather than one, the design team
chose 36 pillows, one for each
10 degrees of cardinal direction,
each pillow following a continu-
ous spiral path from the core to
the perimeter. The choice of 36
pillows allows each pillow to inter-
sect the boundary at an angle that
is not so acute that it is essentially
flat, maintaining a minimum slope
for drainage.
The spiral form of the roof also
borrows from phyllotaxis, the
arrangement of leaves on a plant
stem. When the angle between
the spawning of sunflower seeds
from the central meristem is equal
to Fibonacci’s “golden angle” (the
smaller of the two angles created
by sectioning the circumference
of a circle according to the golden
ratio) the result is an optimal pack-
ing of seeds and a pattern closely
resembling the roof of the Leaf,
which was optimized to a near
constant 10 feet pillow width.
As an aside, the hairy ball theo-
rem of algebraic topology states
that “there is no nonvanishing
continuous tangent vector field
on even-dimensional n-spheres.”
In other words, you can’t comb a
coconut. Any parallel-sided pillow
solution on a compound curved
surface was likely to lead to spirals.
ETFE foil is very thin—less
than 0.5mm—but strong. As
a membrane, it has no flexural
stiffness and relies on prestress
and curvature to span. Prestress
is maintained by the inflation
pressure of the pillows, similar
to a soap bubble. Two pressure
equalized chambers make up the
assembly to provide good thermal
performance with an R-value in
the range of 2.0. Internal pressure
is maintained at about 5 psf in the
summer and 10 psf in the winter
to resist modest snow loads. Heavy
snow fall (up to 30 psf in this case)
will cause the pillow to deflate with
the snow load to be shared by all
three layers of foil. With the three
layers in contact, the R-value drops
to something around 0.1 and the
heat from the biomes quickly
melts the bottom of the snow
forming a slick boundary layer of
water. This precipitates sliding of
the snow to the perimeter, after
which the pillow reinflates.
Cable Net
The cable net for the roof is a
triple layer spiral cable net sup-
porting the spiralling pillows.
The spirals were derived from the
complementary diagonals associ-
ated with a radial/annular grid of
36 radials and annular parallels
at 10’ c/c.
Like membranes, cables have no
flexural stiffness, yet in this case the
system must span as much as 150
feet. Cables rely on curvature and
prestress to span. The job of the
compression chord in a bending
system is done by the boundaries
in a cable net. If a cable experiences
compressive forces, it will instantly
buckle, losing all stiffness. Prestress
is applied to ensure that all cables
remain in tension during all
loading conditions.
The form of the roof is anticlastic,
derived from a rotational hyperbo-
loid, meaning at any given point,
the surface curvature is convex in
one direction and concave in the
other. An anticlastic curve has the
benefit that the prestress in the
convex layer is balanced by the
prestress in the concave layer and
can be maintained in the absence
of external forces such as inflation
pressure.
In order to provide the large
east-facing, overlooking window
at the butterfly garden, the rota-
tional form was split and, rather
than revolving around a continu-
ous ring, the curve was revolved
around a helix. While the net
remains anticlastic, the break
from the pure form complicated
the loads in the boundaries.
The plan of the building, resem-
bling a pair of overlapping beech
leaves, was derived by trimming
the rotated form along selected
spirals, chosen to optimize the
interior spaces to their respective
programs.
Introducing three layers to the
grid (as opposed to simple radial-
annular or two complementary
diagonal spirals) adds indeter-
minacy and complication to the
behavior. While the spiral net was
crucial for supporting the spiral
pillows, any tailor knows that
fabric cut on the bias is stretchier.
Radial cables were required in
addition to the spiral net to pro-
vide stiffness.
The three layers of the net were
described as the Radials, the
The spiral cable net of the Leaf's roof supports inflated ETFE pillows, similar to those used at
the Eden Project in the United Kingdom (shown).
Mollusc shells are built with a single
continuous strip of calcium carbonate in a
spiral form to create an ever-expanding
cone of constant proportion. Designers used
this principle to construct each of the roof's
ETFE pillows following a continuous spiral
path from the core to the perimeter.
According to the hairy ball theorem of
algebraic topology, any parallel-sided
pillow on a compound surface was likely
to lead to spirals. In other words, you can't
comb a coconut.

33. AUGUST 2024 33
Positive Spirals, and the Negative
Spirals, positive and negative
determined based on the “right
hand rule.” Negative spiral cables
by Redaelli are single 24mmØ
Locked Strand cables and were
designed to have constant prestress
over their length of around 15 kips.
Positive spirals are pairs of 16mm
locked strand cables, prestressed
at roughly 7.5 kips to balance the
negative spirals. Radial cables,
locked strand cables ranging from
52mmØ to 64Ø, accumulate load
at each “node” (the points where
the spirals intersect the radials)
at roughly 40 kips per node to a
maximum tension of about 250
kips in the longest radial.
Under balanced load conditions
the pillows pull equally horizon-
tally on their extrusions and little
lateral force is resolved into the
net. But in a snowfall event, the
snow can’t be relied on to be uni-
formly distributed nor to slide at
the same time in adjacent pillows.
A condition with full snow on one
pillow and none on the adjacent
pillow is a very real possibility.
Additionally, the pillows must be
lifted roughly 18 inches above the
negative cables to ensure that they
don’t bear on the crossing cables
which would result in premature
wear. The result is that unbalanced
loads place large torsional forces
on the extrusions and the paired
positive cables. Anti-rotation
cables complete the net, installed
below the negative cables.
The node elements, resembling
huge prehistoric bugs, consist of a
top and bottom clamp plate with
a machined cable groove affixed
to the radial cables with torqued
high strength bolts. A third clamp
plate clamps the negative cables in
place in a curved groove. Positive
cables, lifted roughly 10 inches
above the negative cables, are
clamped in place atop a steel post.
The final piece, an S-post, is bolted
to the bottom to connect the anti-
rotation cables. The geometry of
each of the 333 nodes is unique,
accommodating the subtle differ-
ences in cable incidence angle and
forces. Geometries were precisely
determined to attempt to limit the
“kink” as the cable passes in and
out of the clamp to less than 1.5°.
Partitions
Like the roof, the interior par-
titions separating the biomes
consisted of ETFE foil supported
by cables. Rather than pillows and
spirals, however, the structure of
the partitions resemble a bat’s wing,
consisting of a single layer of ten-
sioned foil membrane spanning
between vertical cable stiffening
elements. The vertical cables them-
selves are supported from catenary
cables below the roof.
The cable wall was designed to
limit the lateral movement under
an interior wind pressure of 5 psf
to H/36, requiring significant pre-
stress. Those vertical cable forces
would result in enormous catenary
cable forces should the catena-
ries follow the roof profile—a
requirement to achieve environ-
mental separation of the biomes.
To address this, the vertical cables
were supported by a very deep cat-
enary cable, and a second set of
vertical cables span between that
and a shallow catenary cable that
follows the roof profile. The upper
set of cables span a much shorter
distance and, as a result, require
less prestress. The prestress on the
16mmØ lower and upper wall seg-
ments are roughly 10 kips and 2.5
kips, with the large catenaries car-
rying up to 150 kips of prestress.
While the ETFE system is strong
with excellent light transmission
characteristics, it is vulnerable to
The spiral cable net supporting the roof has no flexural stiffness and relies on curvature and prestress to span as much as 150 feet.

34. STRUCTURE magazine 34
contact damage and is not “vision
clear.” Glass was chosen for the
bottom 3m of the partitions to
allow views into the biomes.
The partition enclosing the
Butterfly Garden presented a sepa-
rate challenge. While the height
of the partition is much shorter,
the partition curves in plan to
follow the edge of the leaf-shaped
platform. Lateral stay cables were
installed following the radial lines
of the roof to pull partition into
its correct alignment.
Cast Steel in the
Diagrid Core
The diagrid core is the spine of
the building. It contains the verti-
cal circulation to access the event
spaces and the Butterfly Garden,
as well as housing the mechanical
equipment for the inflation of the
pillows and environmental con-
trols for the building and biomes.
The structure of the diagrid does
the heavy lifting for the building,
resisting the gravity and lateral
loads for the roof and provid-
ing the tension ring function to
anchor the cables of the cable net.
The diagrid form was developed
for its structural rigidity as much
as its aesthetic impact. The hori-
zontal elements within the diagrid
form a pair of parallel helixes, each
rising 30 feet per revolution. The
formal reference to the DNA mol-
ecule is evident.
Less evident is the functional
precedent in the grain of trees.
According to The Gymnosperm
Database, It (spiral grain) has also
been noted that spiral grain may
make the tree stronger and better
able to withstand stresses caused
by wind, particularly if the direc-
tion of the spiral is periodically
reversed." (https://www.conifers.
org/topics/spiral_grain.php)
A further functional solution
borrowed from dendrology is
the soft flaring of the branches at
intersections. The diagrid incor-
porates 81 six-limbed ductile cast
steel nodes weighing between
1,500 lbs. and 2,500 lbs. each.
The branch intersections of the
cast node geometries mimic this
natural aesthetic with softened
fillet transitions. These fillets
reduce stress risers and improve
the performance and reliability of
the joints.
The freeform capabilities of cast
steel geometry further enabled the
diagrid form by facilitating the
helical revolutions along the height
while allowing the intermediate
elements to remain straight-cut
pieces. The castings, designed
and supplied by Cast Connex,
included precision-machined
branch-ends to minimize toler-
ances and support fabrication.
Each branch-end included a bev-
elled nose to create grooves for
the circumferential welds to the
incoming HSS members. The
diagrid was shop fabricated in
large assemblies, carefully planned
based on shipping constraints, to
minimize field welding.
A unique feature of the cast nodes,
proposed by Cast Connex, is the
centerline eccentricity. Rather than
a single concentric work point,
the node has two works points,
eccentric from one another by
slightly less than one pipe diam-
eter. This eccentricity results in
bending (which every good engi-
neer tries to avoid), but as a fully
welded frame, some bending is
inevitable. Casting use precludes
local HSS connection limit states
enabling smaller member sizes
than otherwise needed, which in
turn helped reduce overall ton-
nage. Introducing this eccentricity
also dramatically shortened and
lightened the casting, making the
whole system more economical.
Rather than attempting to con-
ceal this eccentricity, the design
team elected to celebrate it with
a continuous soft vertical groove.
The unique geometry of the nodes
earned them the nickname “hockey
pants,” an appropriate metaphor for
a Canadian winter city.
The Skywalk
Where the transparent partitions
provide visual access to the biomes,
the skywalk provides a physical
connection to the tree canopy,
Cantilevering out of the elevator
lobby, it loops back to terminate
at the Butterfly Pavilion passing
the top of the waterfall. The load
is primarily carried by the shorter
inner girder, a torsionally rigid
square hollow steel section, con-
nected for both moment at torsion
at each end. Purlins cantilever
from this inner girder to pick up
the floor and are connected at the
outer end by a continuous curved
channel.
Roughly halfway along the length
of the bridge it is propped by a
pair of round hollow steel struts
terminated with CastConnex
Universal Pin connectors. These
struts significantly increase the
stiffness of the bridge in normal
service conditions. In order to
keep them visually light and
maintain a high-quality finish,
these elements received no fire
protection. In the event of a fire,
these elements are considered to
have failed. The bridge has been
designed to maintain its integrity
in the absence of these elements to
allow safe exit for the occupants.
The Stays and
the Raft
Approaching The Leaf, one is
first struck by the gentle sweep of
the spiral roof. Moving closer, the
angled cable stays radiating from
the perimeter of the building come
into view.
In a cable net, the job of the
compression chord is done by
the boundary. Often this consists
of a compression ring around
the perimeter. Sometimes these
boundary forces are taken into the
earth, a strategy employed by the
Banyan tree.
A compression ring at the eave
was not possible on this proj-
ect because of the desired visual
lightness of the eave and the com-
plications created by the split. The
soil conditions in Winnipeg are
challenging and not suitable for
resisting large tension loads. The
solution was to create a closed
system, with all forces resisted
The Leaf's interior partitions resemble a
bat's wings and consist of a single layer of
tensioned ETFE foil membrane supported
by cables.

35. AUGUST 2024 35
internal to the structure, below the
ground, so that the foundations
carry only the weight of the build-
ing. Transferring the horizontal
loads through a raft diaphragm
wasn’t feasible because the raft
would interfere with the interior
landscaping. A pile supported
raft compression ring was buried
below the ground, outside the
footprint of the building, with the
forces transferred to the ring with
diagonal stay cables. The raft acts
as ballast, balancing the vertical
components of the stay forces, as
well as transferring the horizontal
components around the building.
At the rear of the project, the sup-
porting “bar” building fulfils the
function of the raft slab, transfer-
ring the loads through the building
structure to the foundations.
Erection
The conception and design of
this project was a tremendous
technical challenge. Equal to
that was the erection planning.
Design is done as though the
structure materializes instantly
and perfectly. In reality, the struc-
ture is erected piece by piece, and
cables are installed one at a time.
Each element is imperfect, and
each dimensional variance has
an impact on the distribution of
forces in the structure.
The key to success is toler-
ance. Providing broad guard
rails ensures the car stays on the
road. Each cable was terminated
with an adjustable pin fitting.
The pins allow rotation about
their axis; adjustable fittings can
correct length tolerance and facili-
tate tensioning. Nonetheless, the
guard rails are not always wide
enough. Cables and pillows were
fabricated concurrent with the
structural steel based on objec-
tive perfect geometry. Pins allow
rotation only about one axis,
and steel tolerances in a project
with a complicated geometry are
difficult to achieve. Extensive sur-
veying and some amount of field
rework was required to ensure
that the structural supports were
compatible with the fabricated
net and pillows. Where rework
was impractical, the net was
recalibrated to suit the existing
From the sky, the building resembles a pair of overlapping beech leaves, which was derived by trimming the rotated form along selected spirals.

36. STRUCTURE magazine 36
David Bowick, P.Eng., is a principal
at Blackwell Structural Engineers
in Toronto, an innovative structural
design practice with expertise in ten-
sion and fabric structures, in addition
to timber, concrete and steel. Bowick
is a frequent lecturer and writer and
an adjunct professor at the Daniels
School of Architecture at the University
of Toronto.
boundary conditions.
Each step in the erection redis-
tributes forces in the structure, and
each element must be confirmed,
which the design team did, work-
ing on behalf of the contractor.
Cable contractors, Redaelli and
Tensile Integrity, would propose a
sequence of installing and tension-
ing cables. The design team then
would analyze each step to verify
strengths and calculate movements
in the structure. If a step created
an unacceptable condition—such
as overstress—the plan would be
adjusted.
The goal was to develop a
sequence of installing and ten-
sioning cables that would result
in an acceptable final prestress
condition in the net that is safe
and rigid, and as close as possible
to the target model.
The net was tensioned in roughly
39 steps, each cable being adjusted
up to three times and each step
tensioning six cables until the pre-
dicted tensions and set-outs (the
predicted position on the adjuster
associated with the desired pre-
stress) were reached. The erection
proceeds in a forward direction,
adding tension and taking up
adjustment in order to reach the
correct target; the analysis steps
were completed backwards, starting
with the target model and relax-
ing each stage. For each stage of
the erection, the strength of each
member was verified, as was the slip
of each node clamp and the kink
angle of the cable at the clamps.
Movements of the supporting
columns and stays were calculated
and reported. These values, along
with the measured tension from
the tensioning jacks, were used to
validate each stage. This informa-
tion was reported to the contractor
in a single spreadsheet exceeding
100 MB in size. They distilled this
into a series of field work sheets to
inform each day’s work.
Software Support
Two approaches were taken in
the design and representation of
this project.
The cable net, diagrid, and
supporting elements were mod-
elled and designed using NDN,
a large deformation non-linear
finite element package specifi-
cally created for the engineering
of membrane structures. The
ETFE pillows themselves were a
delegated design, with engineer-
ing completed by the contractor,
Vector Foiltec. The design team
worked closely with Vector Foiltec
to ensure that the cable net pro-
vided adequate torsional rigidity
to maintain stability of the pillows
and extrusions under unbalanced
load conditions.
These components were
modelled and drawn for the
construction documents using
Solidworks, which is effective
for complex, non-orthogonal
geometries and multi-level assem-
blies. Solidworks models can be
exported to .ifc and other for-
mats to integrate with Revit,
Tekla and other software used
by coordinating disciplines and
trades.
The bar building was analysed
and designed using Etabs with
input loads at the interface coming
from NDN. The bar building was
also incorporated into the NDN
model for validation of the Etabs
results. This portion of the project
was modelled for representation
using Revit which allowed close
coordination with the architects
and was also used by the steel fab-
ricator to assist in preparation of
shop drawings. ■
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38. STRUCTURE magazine 38
Indiana Farm Bureau's original Swine Barn, which was just a roof and floor and only
occupied for two weeks out of the year, was transformed into a year-round, multi-
purpose space—just in time for the 2023 Indiana State Fair.

39. AUGUST 2024 39
MULTI-
PURPOSE
MARVEL
STRUCTURAL ENGINEERS AND ARCHITECTS
COLLABORATED ON A YEAR-ROUND
MULTI-PURPOSE VENUE AT INDIANA’S
HISTORIC PAVILION.
BY KEVIN SHELLEY, AIA, LEED AP, SCOTT CLORE, PE,
AND MICHAEL ROACH, PE
T
he complex design of the Indiana Farm Bureau (INFB) Fall
Creek Pavilion project on the Indiana State Fairgrounds
campus was a collaborative effort between architects at
Schmidt Associates and structural engineers from Lynch,
Harrison & Brumleve, Inc. and Complete Structural Consulting, Inc.
Over 18 months, from 2021 to 2023, the group designed a notable
example of creative structural engineering. The structural elements
shared in this story not only highlight the firms’ work but also offer
chances for insight and learning through observation and lessons.
Seven years in the making and with $50 million from the Indiana General
Assembly, the INFB Fall Creek Pavilion opened in July 2023 and preserved
history with structural engineering. The structure is a 196,000-square-
footbuilding that caters to the State of Indiana with expanded possibilities.
During the Indiana State Fair, it serves as an exhibition facility, providing
an environment for livestock competitions, historical exhibits, and educa-
tion. With a 120,000-square foot show floor, exhibitors and visitors can
interact, promote agriculture, and participate in various state fair events.
Beyond its livestock focus, the Pavilion’s flexibility can be seen through
consumer and sporting events.

40. STRUCTURE magazine 40
Features include:
• Clear-span space: Boasting 212 feet of clear-span, column and
brace free area, this open expanse allows unobstructed views.
• Ceiling heights: The 28-foot ceiling heights can accommodate
regional and national track and field, basketball, and volleyball
tournaments.
• Agricultural education: Inspired by Indiana’s agricultural history,
Schmidt Associates architects, structural engineering partners,
and a construction administrator designed a 5,000-square-foot
mezzanine inside the main entrance overlooking the show floor
that can be used as display and demonstration space for fair and
show producers.
• Green innovation: To curb odors, 22 overhead doors, scent-
repelling floor surfaces, and a bi-level ventilation system with
one exhaust system for daily use and another for use during the
state fair are part of this design.
• Historic preservation: A restored 1923 north façade with
reclaimed wood from the historic Seine Barn adds to the build-
ing’s 100-year lineage. Four limestone sculpture panels were
added to the south façade to continue the legacy .
A Newsworthy Endeavor
The INFB Fall Creek Pavilion created a multifunctional space for host-
ing events as varied as NCAA indoor track meets, large car auctions, and
annual Indiana State Fair swine competitions. What sets this project
apart is its versatility and the engineering achieved during challenging
times such as the COVID-19 pandemic, supply chain disruptions, and
the requirement to maintain the historic 1923 north façade.
At the time of bidding this project, the production market for open
web steel joists was at capacity, mainly due to the construction of
warehouse facilities for online retailers such as Amazon. The limited
supply for steel joists, especially 200’, three-piece, double-field-spliced
super longspans, presented a significant problem for the design team.
Allocating the necessary production time for a complex and demand-
ing project made costs prohibitive for a traditional joist supplier.
Realizing the need to keep the project on track, a specialty engineer,
Complete Structural Consulting, Inc., was brought on-board so that
the joists could be produced by the steel fabricator using the specifica-
tions of a traditional Steel Joist Institute (SJI) supplier. To achieve this
goal, several design and fabrication procedures were documented and
reviewed among the design team. A quality manual was developed
by the specialty engineer and steel fabricator to document the shop
standards instituted to ensure the SJI requirements were maintained.
The clarity and thoroughness of the documentation provided design
team and the Owner peace of mind while allowing the project to
continue. The tailored design solution ensured the joists and large
trusses, adhered to standards of The SJI, The American Institute of
Steel Construction (AISC), The American Welding Society (AWS),
and the Society for Protective Coatings.
Historic Preservation
Preserving the historic street-level main entry structure on the north
side of the building was identified early on as a critical aspect of the
project. The existing street level was 10 feet higher in elevation than
the exhibition floor and connecting these two elevations while pre-
serving the entry proved to be a significant challenge. Three options
were discussed among the design team and construction manager.
• Building a concrete retaining wall—One option was to
construct a concrete retaining wall to separate the entry from
the exhibition floor. While efficient in design and concept,
construction of the retaining wall would have required sig-
nificant excavation, which could have led to set-back issues
due to the proximity of the existing building.
• Temporary H-piles and wood lagging—Another concept
that was originally favored by the construction manager and
design team, was to install H-pile shoring, pour a concrete
wall against shoring as the finish surface, and eventually
abandon the shoring once the slab on-grade was installed.
• Steel sheet piling—During construction, the shoring
contractor proposed installing steel sheet piling, a simi-
lar sequence as the H-piles and wood lagging but would
allow for a faster schedule since the sheet piles provided
the retainage as a single unit while the H-piles and wood
lagging was a two-part system The downside to this option
was that the fluted shoring profile would need to be filled
with concrete to create a finished concrete surface. Filling
the flutes required a substantial volume of concrete to fill
the void. The extra material cost was offset by the gains of
construction schedule and this option was chosen by the
construction and design teams.
The sheet pile shoring option allowed construction of the new
exhibit and administration areas without compromising integrity. This

41. AUGUST 2024 41
The Indiana Farm Bureau Fall Creek Pavilion has many uses, from state fair livestock exhibits
and demonstrations to sporting events such as track and field, basketball, and volleyball.
HVAC Innovation
Creating an HVAC system that met the needs of different events and addressed the requirements of hosting 1,300 swine meant using
100% outside air to design a system catering to three zones within the building. The fairgrounds, facilities, and maintenance depart-
ment constitute Zone One, which is served by a high-efficiency gas-fired DX rooftop unit. This unit provides conditioned ventilation air to
Variable Air Volume boxes equipped with electric reheat to give precise control over the indoor climate. Similarly, Zone Two, housing the
office area for the Indiana State Police and emergency personnel, follows the same HVAC setup as Zone One. Both zones are designed
to accommodate daily use with a single level of exhaust that isolates fumes from the livestock environment.
The show arena is the third zone. It is a multifunctional space with six 140-ton high-efficiency gas-fired DX rooftop units to provide con-
ditioned ventilation air, accompanied by 12 CFM low-intake exhaust fans and 20 high-volume/low-speed paddle-type fans. This setup
offers flexibility for the State Fair Commission leadership to control rooftop units based on the type of event being hosted.
“We collaborated with the Owner to fully understand their expectations and vision of what the Pavilion would be,” Schmidt Associates
Senior Mechanical Designer and HVAC Project Lead Brad Wallace said. “As a team, we communicated regularly both internally and
with our partners to strike a balance, talk through challenges and develop solutions.”
For the show floor, a concrete broom finish suitable for livestock and easy to clean while controlling odors was ideal for a multi-use
building. Additionally, air conditioning, power, and wash bays on the show floor could keep people and swine comfortable. Finally, bios-
ecurity measures were implemented to reduce the risk of infectious diseases being carried onto the premises. This was done through a
multi-level design with a separation between spectators and exhibitors. Spectators entering on-grade at the Main Street level get a view
15 feet over the show floor, and there is space for exhibiting different livestock breeds without entering the show floor. Bleachers overlook-
ing the show floor also provide a view for visitors.

42. STRUCTURE magazine 42
approach, which used an entire bay to protect the façade, blended new
developments with historic preservation. As such, the historic north
entry elements, including the entry portals, two restroom towers in
the northeast and northwest corners, and office space, were preserved.
The original brick masonry veneer on the north entry was restored
by repointing joints and replacing damaged brick with colorful por-
celain tile cornice, utilizing masonry maintenance guidelines from
the National Park Service. The decision to restore the north entry
required that the entire Pavilion be constructed with a closely matched
brick. The design team was able to find a suitable brick, seamlessly
connecting the new construction to the original look. The design
team also integrated restored and reclaimed wood from the original
structure’s roof deck into the arched ceilings from the original Swine
Barn’s three north entry portals .
Open-Web Joists
The 212-foot clear-span was realized using 126-inch deep, three
piece, double-field-spliced, open-web steel joists. Uniform in their
configuration, these structural members extend across the ceiling,
combining functionality with aesthetics. This integration of form
and function reflects an interpretation of traditional craftsmanship
and a tailored design solution.
The structure presents a simple façade from below, concealing the
robust engineering behind its construction. Early in the design process,
it was decided to use the joists and girders on the primary grids as
key elements in the Main Wind Force Resisting System (MWFRS).
Incorporating the joists into the lateral system eliminated the need for
diagonal bracing, thereby maximizing usable floor space. Continuity
was achieved by field welding the top chords of the joists and girders at
the supports, along with the bottom chords at the stabilizer plates. The
connections at the top and bottom chords restrict rotation, creating a
force couple at the ends of the joists and girders. Close coordination
between the designer of record and the specialty engineering team
ensured that all structural members—the girders, joists, columns, and
their respective connections—worked together to provide adequate
resistance and a clear load path for all gravity and lateral loads. At
several locations, the joists and girders meet at different elevations
at the columns, causing a combined effect of biaxial bending in the
columns. Additionally, the joists were designed for various gravity load
cases to cater to specific event requirements. This included incidental
5-kip bottom chord bend-loads to accommodate rigging and signage,
as well as the capacity to support multiple 40-kip RTU loads without
extra web members that would disrupt the consistent web layout.
The consistent truss geometry also helped to streamline the construc-
tion process for the steel erector. This standardized design allowed for
the development of repeatable methods in the splicing and erection
of trusses, contributing to efficient and expedited completion. The
long-span joists were delivered to the site in three separate pieces,
then assembled in pairs on the ground before being lifted into their
final position and bolted to supporting members. To ensure precise
and consistent geometry, the erector built a large jig for assembling
each three-piece joist on the ground.
Erecting the initial pair of trusses posed a challenge, requiring exact
coordination to keep the first truss stable while positioning and bolt-
ing the second truss with bolted X-bracing to form a stable pair. The
initial lift required four large cranes, one crane to stabilize each half
of the truss pair. Once the stable pair was erected and bolted, each
subsequent truss could be individually erected and braced to the
others with the bolted X-bridging. One the roof deck was welded to
the joists, and provided lateral restraint for the top-chords, the trusses
were fully installed and ready for their full design loads.
The 200’ joists were designed with a 2-inch chord gap to increase
rigidity in the weak axis. This design provided more stability during
erection and minimized the necessary bolted bridging. This design
feature also allowed for larger single-member webs, resulting in fewer
web members. The fabricator, using techniques common for SJI
joist suppliers, crimped up to a 3-inch single-angle rather than using
double angle sections. 2” HSS were also used as web members at
critical locations and vertical web members. This approach provided
more room at each panel point for aligning concentric members as
the single members are in the chord gap, and the double angle webs
are on outside of the chords, resulting in less secondary bending,
Spectators entering the pavilion from the Main Street level get an overhead view of the show floor.

43. AUGUST 2024 43
fewer double angle sections, and further enhancing the openness of
the expansive area.
Unique Challenges and Solutions
Like any large project with multiple teams, the INFB Fall Creek
Pavilion project faced challenges, notably the need to adapt to various
uses. This required coordination and upfront research from stakehold-
ers. The original joist span, planned at 116 feet, was extended to 212
feet during design development to accommodate program require-
ments to enable the Pavilion to host USA Track and Field events.
The onset of the COVID-19 pandemic also halted the project, with
a rebid in 2021. While challenging, this delay provided the teams
time to reassess and refine the project’s design and logistical plans
that led to a more efficient outcome.
The project team also learned valuable lessons in flexibility and adap-
tation. An example was the work with the Indiana Bridge fabrication
shop, which brought the project to life. This hands-on experience and
the Owner’s involvement led to a smooth and transparent process,
highlighting the importance of open communication. Permanent
shoring on the north side of the building proved beneficial. The team
initially proposed a temporary steel H-pile and wood lagging system,
but the contractor proposed sheet metal piling for efficiency. As a
result, even though more concrete was required due to the depth of
the sheet piles that also served as formwork for the lower wall, the
installation proceeded faster, helping to keep the project on schedule.
Beyond Engineering
The INFB Fall Creek Pavilion partnership between Schmidt
Associate’s architects, Lynch, Harrison, and Brumleve, Inc., Complete
Structural Consulting, Inc. engineers, and Indiana Bridge Fabricators
was a multidisciplinary approach to collaboration and problem-
solving. The project not only met functional goals but also did so on
budget, ahead of schedule, and with a level of quality that may be
seen by the public eye.
According to the Owners, air handling and movement of odors, the
loading and unloading of swine, the broom finish on the showroom
floor to provide the right balance of traction for the livestock footing,
cleanability to control surface odors, and the separation of the public
from the exhibitors had to be planned and coordinated before the
2023 Indiana State Fair.
Transforming the previous Swine Barn, which was just a roof and
floor and only occupied for two weeks out of the year, into a year-
round, multi-purpose space, Schmidt Associates architects designed
a facility with a lower grade elevation.
“When the Indiana State Fairgrounds were constructed in the late
1890s, they were built for fairgoers to bring their animals by train, and
they didn’t have to worry about 55-foot trailers,” Indiana State Fair
Commission Executive Director Cindy Hoye said. “This is something
a lot of people don’t consider, but to solve this challenge, Schmidt
Associates considered livestock and people.”
Despite the project’s scope, the team kept costs within the $50 mil-
lion budget. This discipline was achieved through strategic decisions,
resulting in over $1 million in savings.
The INFB Fall Creek Pavilion is a win for Indianapolis and the
State of Indiana due to its ongoing annual economic impact of over
$200 million and the vitality to various sectors, from hospitality and
transportation to local businesses and job creation. In its short life,
the Pavilion has not only enhanced the capacity of the campus, but
it also shows how challenges can become opportunities.
“Undoubtedly, the highlight of the 2023 Indiana State Fair was the
Indiana Farm Bureau Fall Creek Pavilion. The building exceeded all
expectations,” said Indiana State Fair Commission Chief Development
and Strategy Officer Ray Allison. “Through countless conversations during
the Fair, I heard praise for the work we did. People were speechless when
they walked in, and long-time swine exhibitors were emotional.” ■
The 212-foot clear-span was realized using 126-inch deep, three piece, double-field-spliced, open-web steel joists.
Kevin Shelley, AIA, LEED AP, is chief operations officer | principal for Schmidt
Associates. He loves helping Owners realize their visions, and working with them
to achieve more than what they thought was possible. He serves clients in the firm’s
K-12, higher education, community, and healthcare studios.
Scott Clore, PE, became a member of the Lynch, Harrison & Brumleve, Inc. (LHB)
team in 2003 and a principal in 2015. Throughout his time at LHB, he has worked
on large industrial facilities, churches, office buildings, multi-use structures, and
educational facilities.
Michael Roach, PE, is President of Complete Structural Consulting, Inc. (CSC). CSC
specializes in delegated design for connections and misc. metals, industrial design,
and protective structures design. Michael began his career in the steel joists industry
where he authored technical digests, the Special Profile Joists Catalog. His expertise
includes connections, cold-formed, dynamic analysis for protective structures, and
steel joists and deck design.

44. STRUCTURE magazine 44
Supporting a Community
at Asteri Ithaca
The project delivered a conference center as well as affordable housing
to the growing city.
By Cody Gibbens, PE

45. AUGUST 2024 45
O
n the south shore of
Cayuga Lake lies the
city of Ithaca, New
York. The home of
Cornell University, this city faces
the best of times—a high quality
of living and steady growth. With
this growth comes a need for more
parking, more meeting spaces,
more amenities, more housing,
and like many cities across the
nation, more affordable housing.
With these challenges in mind,
BW Architecture and Engineering
partnered with the City of Ithaca
to develop a three-phase proj-
ect which consisted of adding
affordable housing to the area,
the construction of a new confer-
ence center, and the renovation of
the existing Green Street Parking
Garage.
STAND Structural Engineering
teamed with BW Architecture
& Engineering and delivered a
three-story conference center with
nine stories of affordable housing
stacked on top. The lower three
stories house a 55,000 square foot
conference center with multiple
large meeting rooms, a two-story
ballroom, full commercial kitchen,
management offices, and a ground
floor retail space. The upper nine
stories consist of 181 affordable
housing units, 40 of which remain
reserved for people in need of sup-
portive services per the New York
State Empire State Supporting
Housing Initiative (ESSHI). The
residential tower also houses a full
community room, fitness space,
outdoor patio, and conference
room on the top floor with a full
balcony.
System Selection
The design team initially per-
formed an extensive system
selection exercise to determine and
select the best structural system
for the project. Early on in this
process, the team determined that
the main challenge was laying out
a column grid so that the columns
would have a minimal impact
within the ballroom spaces. The
primary options explored were:
Option 1: Utilize a conventional
composite steel framing system.
Although a natural place to start,
the downside of this system is that
to maximize the spans, a deeper
structural depth is required in the
residential tower portion of the
building. This deeper structural
depth would result in eliminating
an entire floor since the overall
building had already been near
the code specified height limit.
Option 2: Utilize precast
hollow-core planks with upset
support beams. This would entail
creating custom T-shaped mem-
bers that would span the units
for the precast planks to bear
on. This option minimized the
depth of structure needed, but it
did not maximize the spans and
overall created a heavier system
as compared to other evaluated
systems.
Option 3: Design a four-story
composite steel podium designed
to clear-span over the ballrooms
below. This hybrid system uses 4
stories of composite steel framing,
paired with 8 stories of load-bear-
ing cold-formed walls stacked
above. This structural scheme
would allow for the individual
requirements of the two main
zones of the building to each be
met. Throughout the conference
center the composite steel system
allows for the flexibility to design
around a non-repetitive layout, as
compared to a cold-formed wall
system above which better suits
the repetitive nature of the apart-
ment units.
After evaluating the three sys-
tems, as well as additional options
not discussed, the design team
chose to move forward using
Option 3—the Hybrid Steel
Podium.
Spanning the
Ballroom
After selecting the overall general
structural system for the building,
designing an element to clear span
the ballroom and support eight
stories of residential space above
presented the next challenge.
The design team chose to explore
various custom steel truss designs
that would span between columns
located along the exterior edges of
the ballrooms.
One of the primary concerns with
the truss design was deflection
throughout the construction of
the project. If the trusses deflected
too much during the construction
process, the cold-formed strap
bracing in the shear walls could
buckle and require refastening or
the gypsum wall sheathing could
crack as the lower levels begin
finishing.
The design team made two criti-
cal design decisions at this point.
First, they reduced the overall
weight of the residential tower by
using lightweight concrete for the
construction of the tower floors
rather than conventional normal
weight concrete. Even by doing
this, since the design live load for
residential spaces is 40 psf, roughly
75% of the load applied to the
trusses consisted of dead load.
Second, they designed the trusses
to a very stringent deflection limit
of L/600 for the total load deflec-
tion and a max deflection of 3/4
inches for dead load deflections.
With these two decisions in mind,
Structural Engineer of Record: STAND Structural
Engineering
Architect of Record: BW Architecture & Engineering
Contractors: Vecino Construction—Tower
Construction, Welliver—Conference Center
Construction
Steel Fabricator: JPW Companies
Project Team
Figure 1. This rendering shows the building section through center truss. The wall trusses
spanned the entire 4th floor.

46. STRUCTURE magazine 46
the team decided on a one-story
deep wall truss.
As seen in Figure 1, the wall
trusses spanned an entire floor,
with the 4th floor being the
bottom chord and the 5th floor
being the top chord. At the south-
ern portion of the truss outside
of the ballroom area, the truss
deepened from 15 feet deep to 23
feet deep. The overall length for
each truss measured 115 feet with
a maximum clear span between
supports of 75 feet. Four of these
trusses were used spaced at 30 feet
on-center with composite floor
framing spanning between them.
For the fabrication and erection
of the trusses, the steel fabricator
responsible for the trusses and all
steel throughout the project, JPW
Companies out of Syracuse, New
York, elected to shop fabricate
the wall trusses in four separate
sections for easier transport. Per
standard practice in the New York
area, all connections on the trusses
were to be bolted connections.
Once on site, the crane would
hoist the sections of the truss into
location and workers would field
bolt them into place.
Lateral System
For the lateral force resisting
system, the team used a combina-
tion of cast-in-place concrete shear
walls, light gauge cold-formed
shear walls, and steel braced
frames. Between all these systems,
the full height concrete shear walls
making up the stair towers and ele-
vator cores function as the lateral
element that resists most of the
lateral load from the residential
tower. The light gauge shear walls
primarily resist the wind loading
from the nearly 20-foot-tall para-
pet and screen walls. And finally,
the steel braced frames act as the
main lateral element for the steel
podium for the lower five stories.
During the bidding process,
contractors Vecino Construction
and Welliver elected to bring
Vulcraft on board with its Vulcraft
RediCor system in place of the
previously designed cast-in-place
concrete shear walls. By making
this change, the stair towers and
elevator cores would be pre-
manufactured in modules at an
offsite facility that would then be
transported to the site and could
quickly be erected. One of the ben-
efits of switching to the RediCor
system included the immediate
stair access to all floors once work-
ers installed the modules. At the
time of construction, this project
utilized the tallest RediCor stair
core to date at a height of 152’-6”
and the tallest four-sided elevator
shaft RediCor had produced to
date at a height of 145’-6”.
Site Challenges
The project site provided its fair
share of challenges. Three sides
of the building contained utility
easements, sewers, or electrical and
telephone vaults located within
12 inches of the face of the pile
caps. Due to the location of these
elements, the building needed to
incorporate cantilevers into the
design since foundations could not
be installed in these areas. These
conditions led to the development
of one of the signature focal ele-
ments of the building—the double
skewed columns at the Southeast
corner of the building as seen in
Figure 4.
The foundation design of the
building also posed considerable
hurdles. Even though the exist-
ing building located across the
street bears directly on bedrock,
preliminary borings at the start
of the project revealed that rock
Figure 2. Truss T02 section 3 of 4 is erected.
Figure 3. This image provides a sense of scale for the trusses in the community room.
Figure 4. Due to site conditions,
cantilevers were utilized in multiple
areas around the building.

47. AUGUST 2024 47
was not located within 100 feet
of finished grade on our site. With
the columns that support the main
trusses supporting loads upwards
of 2,000 kips, the team decided to
use 100-ton steel H-piles as the pri-
mary foundation system. During
the bidding process, the initially
designed foundation system
switched to the Menard USA’s
proprietary controlled modulus
columns. These controlled modu-
lus columns are 18-inch diameter
vertical grouted elements which
displace soils laterally, produc-
ing little spoils. With this being
a drilled system versus the driven
H-piles, the disturbance to the
surrounding building and neigh-
borhood was greatly reduced, as
well. That decision alone saved the
project nearly $400,000.
Conclusion
The Asteri Ithaca project over-
came many challenges throughout
its design including design con-
straints and economic hurdles, not
to mention a pandemic sweeping
the nation at the start of construc-
tion. Upon its completion this
project now stands as a pillar to
help support the City of Ithaca,
be it through the city’s new confer-
ence center and its ability to bring
new commerce and events to the
city or the residential tower and
the opportunity it brings to help
house more of the ever-growing
community of Ithaca, NY. ■
Cody Gibbens is an Associate Principal at STAND Structural Engineering.
([email protected])

48. STRUCTURE magazine 48
Ready
to Meet
Changing
Needs
The structural systems at the new Washington
University School of Medicine Jeffrey T. Fort
Neuroscience Research Building needed to
accommodate ever-evolving needs of the research
groups. By Kurt Bloch, SE and Julie Shaw, PE
D
esign for the modern
scientific workplace
is most successful
when the architec-
tural and structural configuration
of a building is directly linked to
its purpose. This philosophy dic-
tates that a research facility should
be much more than a controlled
environment for academic study;
it should actively support and pro-
mote the science within.
Seeking to become the nation’s
leading research program for
National Institutes of Health
(NIH) funding, stakeholders in
the Washington University School
of Medicine (WUSM) in St. Louis,
Missouri, envisioned a laboratory
facility that could readily adapt to
the rapidly evolving science happen-
ing within. They wanted a building
with dynamic spaces for research
collaboration across a broad range
of diverse but related disciplines
to accelerate the development of
“bench-to-bedside” treatments and
improve patient outcomes.
Now completed, the Jeffrey
T. Fort Neuroscience Research
Building (NRB) is one of the
largest facilities of its kind in
the United States. The 11-story,
609,000-square-foot NRB is home
to more than 100 research teams
working together in a building
where architectural and structural
design is intrinsically tied to the
goals and needs of the institution.
Research Flexibility
One of the most important guid-
ing principles of the design was to
create a research environment with
the flexibility to adapt as needs
evolved. Rather than the typical
approach of assigning space based
on departments, WUSM planned
the layout of the research spaces
around specific themes to facilitate
team-based science beyond that of
traditional departmental bound-
aries. As a result, the structural
systems were required to accom-
modate the ever-evolving needs of
these research groups throughout
the life of the building.
Given these requirements,
The sun rises on the new Jeffrey T. Fort
Neuroscience Research Building at
Washington University School of Medicine
in St. Louis

49. AUGUST 2024 49
reinforced concrete proved to
be the optimal structural system
for the project. In keeping with
local construction practices, the
design features a one-way pan joist
floor system that spans between
concrete beams. In addition to pro-
viding a vibration-resistant floor
that efficiently balances damping
and self-weight, a pan joist floor
can accommodate future floor
openings and penetrations more
easily than a comparable two-way
flat slab system.
As part of a broader strategy to
maximize flexibility, all labora-
tory spaces were designed to meet
a Vibration Criteria (VC) of 2000
µ-in/s, or VC-A, to satisfy typical
requirements for sensitive equip-
ment. A 10-foot cantilever along
the building perimeter at each floor
was reserved for office spaces and
designed to satisfy an acceleration
limit of 0.5%g for occupant comfort.
The use of RAM Structural
System and RAM Concept guided
the design toward a cost-effective
solution with an optimized column
grid of 21 feet by 31.5 feet. A
Owner: Washington University School of Medicine
Architect: CannonDesign, St. Louis, MO, and
Perkins+Will, Chicago, IL
Lab Planning: CannonDesign, St. Louis, MO,
Perkins+Will, Chicago, IL, and Jacobs, New York, NY
Structural Engineer: CannonDesign, St. Louis, MO
MEP/FP Engineer: CannonDesign, St. Louis, MO
and AEI, Madison, WI
Vibration and Acoustical Consultant: Colin Gordon
Associates, Brisbane, CA
General Contractor: McCarthy Building Companies,
Inc, St. Louis, MO and KAI, St. Louis, MO
Project Team

50. STRUCTURE magazine 50
6000-psi concrete mix was used
for the structural framing to opti-
mize the size of the columns and
improve the vibration and deflec-
tion performance of the slab and
framing due to the higher stiffness
properties. Typical lab space floor
system consisted of a 6-inch slab
over 14-inch-wide by 14-inch-
deep concrete joists (22-inch total
structural depth) utilizing 53-inch
wide pans. 42-inch-wide girders
spanning between the columns
matched the 22-inch joist depth.
The vibration performance of
this design was initially evaluated
using RAM Concept and then
verified by vibration consultant,
Colin Gordon Associates (CGA),
using their own proprietary finite
element modeling software. To
balance efficiency and adaptabil-
ity, floors dedicated to mechanical
systems were only designed to meet
strength and deflection require-
ments. Despite the higher applied
load to the floor to accommodate
the mechanical systems, the con-
crete joist web widths were reduced
from 14 inches to 10 inches and
the concrete girder web widths
were reduced from 42 inches to 36
inches with the structural depth
remaining consistent at 22 inches.
A Heavy Load
Unlike the 15.5-foot story
heights for the typical lab spaces,
the mechanical rooms located in
the basement, second-floor, and
eleventh-floor feature 22-foot to
24-foot story heights to accommo-
date double stacked air handling
units. Additional concrete beams
were required to support the
localized heavy equipment on the
second floor and eleventh floor,
and supplemental reinforcement
was provided in the slab above to
support the substantial point loads
imparted by suspended piping
and ducts. Planned plumbing
penetrations on all floors were
accommodated by sizing and
reinforcing the girders to include
an allowance for 4-inch diameter
sleeves.
The depth of the basement
level, coupled with the effects of
surcharge loads, required 22-inch-
thick concrete walls around the
perimeter of the building. The
first structured floor above the
basement was designed to support
an extensive system of steel-framed
catwalks, mechanical equipment,
and suspended elevator pits.
Because the basement has a larger
footprint than the structure above,
portions of the first-floor slab were
designed to accommodate drive
lanes that provide access to a new
garage located immediately south
of the research building. These
portions of the structure feature
closely spaced pan joists to sup-
port multiple topping slabs, soil,
sidewalks, and vehicle traffic.
Despite the challenges posed
by the construction of the base-
ment level, a significant benefit
was realized from the improved
soil conditions, rock bearing, and
skin friction capacity present at
the depth of excavation. Even with
the heavy loads applied to each
column, drill pier sizes for the
foundation system were on average
42 inches in diameter with 9-foot-
deep rock sockets. In addition, the
geotechnical investigation of the
subgrade conditions established
that a soil site classification of
B would be appropriate for the
NRB, which lowered the Seismic
Design Category from typical C in
St. Louis to B. This development
provided the welcome benefit of
reduced seismic loading, which
was particularly beneficial given
the mass of the building, and
reduced requirements for non-
structural seismic bracing within
the facility.
Supporting a Range
of Uses
The building’s design needed to
provide spaces for both laboratory
research as well as collaboration/
knowledge transfer. A grand
atrium space and an auditorium
on the first floor were central to
realizing a building that actively
fosters knowledge sharing. The
program needs for each of these
spaces could not be accommo-
dated within the standard column
grid, so story-high transfer beams
were designed to support the
eleven stories above that could be
constructed within the second-
floor mechanical space.
Above the atrium, a concrete
beam cantilevers 11 feet from the
shear walls that wrap around the
elevator core. At the auditorium,
a story-high beam spans 72 feet
between columns to support a
column above that transfers near
the middle of the span. The design
of the transfer beam above the
auditorium was complicated by
the need to accommodate a door
through the member. Analysis of
each transfer beam was performed
using the strut and tie method
with validation from RISA 3-D.
Schematic of full-height beam above atrium and auditorium.
Construction of muti-story round concrete columns cast monolithically with use of SCC
concrete mix.

51. AUGUST 2024 51
Near the facade, the grand atrium
is open further from the first level
to the underside of the fourth
level, resulting in a ceiling height
of nearly 76 feet. Rising unbraced
through this space, large 44-inch
diameter concrete columns at the
perimeter of the building support
wind girts to which the curtain
wall is attached. Given these con-
siderations, it was essential to cast
each column in a single pour or
incorporate moment splices at
each cold joint. Leveraging their
previous experience, McCarthy
chose to construct each column
monolithically using a special-
ized self-consolidating concrete
(SCC) mix.
Seamless Connection
WUSM is affiliated with BJC
HealthCare, which includes
the nationally recognized
Barnes-Jewish Hospital and St.
Louis Children’s Hospital. These
facilities are connected across the
medical campus by an extensive
system of skywalks. To connect
the NRB visually and physically
with the rest of the campus, this
network needed to be extended
through the construction of a new
pedestrian bridge that, in addition
to enhancing movement across the
campus, serves as a bold design
statement.
To replicate the aesthetic of the
current pedestrian skywalk system,
the new bridge incorporates can-
tilevered concrete columns that
support long-span steel girders,
the longest of which spans 120
feet. Because the columns sup-
porting the bridge are categorized
A full-height transfer beam above the auditorium
supports eleven stories of loading.
Typical pan joist construction selected for vibration performance and future flexibility.

52. STRUCTURE magazine 52
as a cantilever column lateral force
resisting system and designed to
meet Seismic Design Category C,
the 2018 International Building
Code and Chapter 12 provisions of
ASCE 7-16 restricts the permitted
column height to 33 feet, 11 feet
below what the design required.
Posed with this challenge,
the team turned to the 2009
AASHTO Pedestrian Bridge
Code for guidance. Unlike IBC,
this design code does not have a
prescriptive height limit for the
seismic design of cantilevered
column systems, though its appli-
cation to a building structure
required engineering judgement.
To overcome this hurdle, the
design team sought a variance
from the City of St. Louis, which
proposed using the most strin-
gent design forces and detailing
requirements of both ASCE
and AASHTO. Ultimately, the
approach was accepted by the
AHJ. RISA 3D was used for
design of the steel sections, and
use of SP Column was required for
the slender column design.
Although the pedestrian bridge
is structurally independent from
the parking garage it connects
to, structural upgrades of this
existing building were required.
Linking the end of the bridge to
the rest of the pedestrian walkways
required the construction of an
enclosed pathway across the park-
ing structure. The higher live load
within this zone coupled with the
need for a topping slab to create
a level walking surface exceeded
the design capacity of the existing
parking deck.
Collaborative efforts from
CannonDesign, McCarthy, and
specialty engineer Norton and
Schmidt determined that the
most economical solution was
to reinforce the existing garage
using fiber-reinforced polymers
(FRP). The applied loads along
the planned walkway were given
to Norton and Schmidt for
analysis and design of the FRP
system. The top of the existing
slab was scored so that FRP rods
could be inserted to provide
negative flexure reinforcement.
The bottom of the slab and sides
of the existing post-tensioned
beams were reinforced with a
carbon fiber wrap to resist posi-
tive flexure and shear.
A Beacon of Hope
Every aspect of the Jeffrey T.
Fort Neuroscience Research
Building represents a meticulous
response to the institution’s goals,
exemplifying the harmonious
marriage of form and function
between architectural and struc-
tural design. While the design of
this massive building frequently
posed new challenges, each one
offered an opportunity to imple-
ment a creative solution. With
construction complete, the
researchers who now call this
building home can address more
profound sets of challenges as
they seek a deeper understand-
ing of the human neurological
system with the ultimate goal
of improving patient outcomes.
Today, this magnificent structure
stands as a beacon of hope and a
testament to the relentless pursuit
of scientific progress and medical
excellence. ■
Kurt Bloch, SE, and Julie Shaw, PE, are Structural Engineers with the St. Louis, MO,
office of CannonDesign. This article was written in tribute to the late Ruofei Sun, the
EOR of the project and longtime Structural Lead of the St. Louis office. (kbloch@
cannondesign.com and jshaw@cannondesign)
A steel pedestrian link bridge is supported on cantilevered concrete columns.

53. AUGUST 2024 53
Major Changes to ASCE 7-22 Flood Loads
The changes to flood design should significantly strengthen the flood load resistance for structures designed to
these new provisions.
By William L. Coulbourne, PE; Daniel Cox, Ph.D; and Jessica Mandrick, PE, SE
code UPDATES
A
SCE 7-22 Minimum Design Loads and Associated Criteria for
Buildings and Other Structures Supplement 2 was published in
May 2023 and incorporates a complete revision of the flood load
provisions of the standard. Prior to the supplement, the flood load
provisions that are part of ASCE 7 Chapter 5, had been minimally
changed since 1998. In contrast, communities in coastal and riverine
areas have experienced extensive damage and loss from extreme storms
with nine of the 10 costliest Atlantic hurricane seasons occurring
since 2004. As a result, many jurisdictions have sought to increase
flood standards locally. Figure 1 shows severe damage to two recently
constructed houses, both of which were damaged from Hurricane
Michael in 2018 when both were outside the 100-year floodplain.
Building to the new flood provisions would have either made these
houses more robust or they would have been elevated to minimize
flood damage. With many lessons learned and new research conducted
since 1998, the ASCE 7-22 Flood Load Subcommittee strongly felt
that the standard needed to be replaced with up-to-date formulas and
methods. The subcommittee developed a new approach for addressing
the reliability of building design for flood considering climate change
effects, particularly sea level rise. All references in this article to ASCE
7-22 flood loads are to Supplement 2.
The current design requirements in ASCE 7-16 for flood elevation
only required designs to the 100-year flood (the 1% annual chance
flood) plus some amount of freeboard. The use of the 100-year flood
was largely based on the National Flood Insurance Program (NFIP)
Base Flood Elevation (BFE) and did not meet the reliability targets
of ASCE 7. This freeboard added to the Base Flood Elevation was a
fixed amount based of the requirements of NFIP, ASCE 24, or the
local jurisdictions; it was not risk-based and had no particular connec-
tion to the importance of the facility to the community. Dependent
upon site conditions such as the topography and presence of waves,
the freeboard provided inconsistent levels of protection above the
100-year flood. Moreover, ASCE 7-16 applied only to structures
located within the 100-year flood area. Even as some attempts were
made to increase elevation requirements via freeboard, none of this
applied to structures immediately adjacent to the 100-year flood area,
creating a ‘waterfall’ effect.
ASCE 7-16 and earlier editions recognized that the 100-year flood
load did not meet the reliability targets of the standard and assigned a
load factor of 2.0 to coastal A and V zones in an attempt to increase the
reliability. This presented a similar issue to the addition of freeboard.
The load factor of 2.0 scaled the magnitude of the horizontal flood
force but did not scale the elevation of the flood water. The Flood
Load Subcommittee wanted flood design to be based on risk and to
be risk consistent across the country.
A Change in Definition
One of the most significant changes in ASCE 7-22 Supplement 2
is the change in the definition of the flood hazard area. Previously,
structures within the 100-year flood area, or the Special Flood Hazard
Area in the terminology of flood plain management, were subjected to
ASCE 7. However, the new definition calls for the 500-year floodplain
to be the new area of applicability for Risk Categories II, III, and IV
structures. For Risk Category I structures, the 100-year floodplain
remains as the designated flood hazard area. This change has significant
implications for all new construction and substantial improvements
to structures lying between the maximum extents of the 100-year
and the 500-year flood areas.
The new approach can be described as going beyond the National
Flood Insurance Program regulations and requirements. The new flood
load provisions do not tie the loads to a fixed regulatory elevation but
instead use a risk-based approach to determine the flood hazard and
then use the hazard levels to calculate the loads for the selected flood
hazard. The new definition in the revised standard for the design flood
is “The flood corresponding to the design mean recurrence interval
assigned by risk category in accordance with Table 5.3-1, including
Fig. 1 Damage to two houses from Hurricane Michael flooding (2018): right house outside the 500-year floodplain and left house in the 500-year floodplain (Source: FEMA MAT
Report P-2077 for Hurricane Michael).

54. STRUCTURE magazine 54
relative sea level change.” This revised definition includes references
to two major changes in the ASCE 7-22 provisions. One is the link
between flood design, flood return periods, and building risk category.
The second is the inclusion of relative sea level change as part of the
design flood. A reduced version of Table 5.3-1 is shown in Table 1.
The Flood Hazard
The revised ASCE 7 Flood Load chapter now requires the use of a
return period for design based on the Risk Category that ASCE uses
to define use and occupancy classes. As evidenced by the amount of
flood damage, losses, and claims in areas beyond the special flood
hazard area, as shown in Figure 1, the regulatory minimum elevation
that uses the 100-year event is no longer sufficient to reduce losses
caused by flooding.
The solution to the problems of under-estimating the flood hazard
and improving risk consistency is to require flood designs for each Risk
Category to a specified flood return period. The risk categories and
their corresponding mean recurrence intervals are shown in Table 1.
The advantage of using this method is that most buildings fall into
Risk Category II and federally published Flood Insurance Studies (FIS)
typically have 500-year flood elevation data in addition to the 100-
year data and many FEMA Flood Insurance Rates Maps (FIRMs) also
delineate the extent of the 500-year flood plain. The disadvantage of
this method is that the 750- and 1000-year MRI elevations and flood
conditions are typically not published in the FIS or on the FIRM. In
order to determine these larger return period floods, scaling factors
were developed for both riverine and coastal conditions to convert
the 100-year flood elevation to the desired mean recurrence interval.
The table of scaling factors is shown as Table 2. These scaling factors
are also part of the standard Table 5.3-1.
The amount of flood information available from federally published
flood studies varies depending on the amount and type of informa-
tion collected and developed regarding the local floodplain and the
date of the study. Table 2 assumes that 100-year flood elevation data
is available and thus can be used to scale from. The revised standard
addresses the issue of unavailable data, so the user knows how to
proceed to obtain the required design flood elevation.
Flood velocity and wave heights are also part of the flood hazard.
Scaling factors are also provided for those parameters for return
periods greater than 100 years. These are shown in Table 3 and are
in the standard as Tables 5.3-2 (velocity) and 5.3-3 (wave height).
These changes now require the user to select the Risk Category,
determine the flood hazard level and calculate flood loads based on
the design flood depth. In many instances, especially coastal, the
designer may elect to elevate the building above the expected flood
level instead of fortifying the building sufficiently to ‘resist’ the flood.
Another significant change is the inclusion of climate change effects
in the determination of the design flood. The ASCE 7-22 equation
for design stillwater flood depth is: d
f
= (Stillwater elevation for design
MRI—Ground elevation including effects of erosion) + Δ sea level rise.
The revised standard now requires that climate change in coastal flood
plains be considered by adding the change in sea level rise to the flood
depth. The user is to consider the SLR effect over a 50-year period, the
minimum of this change effect is to be a straight-line extrapolation of
the historical SLR. Other more conservative approaches may be used
including projections made by the U.S. Army Corps of Engineers
(USACE) a link to the Corps projections is provided in the standard.
The Corps data makes projections for a low, intermediate or high
rate of SLR until the year 2100. Those projections allow the user to
make a choice of which rate is the most appropriate for their design
condition or which rate best suits the needs of the client.
The new chapter also includes guidance on the amount of scour
to consider for columns and walls under breaking and nonbreaking
wave conditions.
Flood Load Formula Changes
There are changes to several flood load formulas in addition to the
changes made in defining the flood hazard.
1. Flood velocity has been reduced to: V = C
v
√gd
f
, where C
v
is a
velocity coefficient taken as 0.5, g is acceleration due to gravity, and
d
f
is the design stillwater flood depth. This change was made based
on extensive study by the USACE on velocity of coastal floods; the
method previously used in ASCE 7 was thought to be very conserva-
tive and the recent Corps study has confirmed that thought. Figure 2
illustrates the results of the velocity study data points in comparison
to ASCE7-22 and ASCE 7-16 formulas.
2. Calculation of wave loads was changed to follow the Goda method.
This method depends on adjusting the wave load effect on a building
with the height of the wave and the depth of the building in relation
to the still water level. Wave wash up on a wall is also considered if
the wall is located such that the wash up effect can occur. Figure 3 is
one of the new wave conditions showing the bottom of a building
partially submerged below the stillwater level. The Goda equations
Risk Category Mean Recurrence
Intervals (MRI)
Annual Exceedance
Probabilities (AEP)
I 100-year 1.00 %
II 500-year 0.20 %
III 750-year 0.13 %
IV 1000-year 0.10 %
Table 1. Risk Category vs. MRI
Risk
Category
Scaling
Factor-Gulf
of Mexico
Scaling Factor-
All Other
Coastal States
Scaling
Factor-
Great Lakes
Scaling
Factor-
Riverine
Sites
I 1.00 1.00 1.00 1.00
II 1.35 1.25 1 .15 1.35
III 1.45 1.35 1.20 1.45
IV 1.50 1.40 1.25 1.50
Table 2. Scaling Factors for Other Flood Elevations Based on 100-year Elevation
Risk CategoryScaling Factor-Maximum
Velocity for All Coastal States
Scaling Factor-
Controlling Wave
Height
I 1.00 1.00
II 1.35 1.30
III 1.45 1.35
IV 1.50 1.40
Table 3. Scaling Factors for Maximum Velocity and Controlling Wave Height

55. AUGUST 2024 55
William L. Coulbourne, PE, F.SEI, F.ASCE, Coulbourne Consulting, has 50 years of
experience as a manager, designer, and building professional. He is a member of
ASCE 7 standards committees on flood loads.
Daniel Cox, Ph.D, M.ASCE, is a professor at Oregon State University. His research
focuses on community resilience to coastal hazards, including tsunami and hurricane
surge and waves inundation.
Jessica Mandrick, PE, SE, M.ASCE, is Partner at Gilsanz, Murray, Steficek. She has a
wide range of experience in multiple disciplines with specialties in education facilities,
renovations, and buildings in the floodplain. Mandrick is also a member of the
STRUCTURE magazine Editorial Board.
allow the determination of the pressure profile acting on the building,
as opposed to the previous breaking wave formula which was applied
as a concentrated force at the stillwater elevation.
3. Flood-borne debris design criteria has been added; the provisions
and methods are patterned after those used in Chapter 6 on Tsunami
loads. Risk Category I structures are exempt from the debris design
criteria, as are one- and two-family dwellings, and Risk Category II
buildings outside of the special flood hazard area. The chapter speci-
fies the types of debris and their properties (threshold depth, mass,
stiffness) to be considered for each risk category. Engineers should
note that for a debris impact, the stiffness of the impacted structural
element (weak axis bending stiffness of a wall or bending stiffness of
a column) may often be considerably less than the axial debris stiff-
ness. Considering the stiffness of the impacted object, as permitted
by the standard can significantly reduce the debris impact load.
4. A method has been added to be able to determine if the site is
subject to either non-breaking or breaking waves. The difference in
wave loads from these two conditions can be significant.
5. Load combinations for various flood conditions have been deter-
mined so that the total flood load is used in the application of the
appropriate load combination from ASCE 7, Chapter 2. The com-
binations cover both riverine and coastal floods. For example, the
flood load combination for coastal flooding is the sum of loads from
hydrostatic, hydrodynamic, and waves or debris impact applied to
the design element of interest. This sum is Fa in the load combination
used in Chapter 2.
6. Additional provisions are included to determine if either a sliding
or overturning condition might affect global stability. Both of these
stability load combinations are in addition to those in Chapter 2.
7. A section has been added for Performance-based Design (PBD)
for Flooding. This section points to the already permitted use of PBD
in ASCE 7 and provides some guidelines on how to follow the PBD
process for flooding.
The calculations for hydrostatic loads are included in the supplement,
and they require that the soil be considered fully saturated unless a
seepage analysis in the geotechnical report determines otherwise.
The calculations for hydrodynamic load are included in the supple-
ment and the reduction in the maximum velocity can significantly
reduce the hydrodynamic pressure as the velocity term is squared in
the equation. There are new provisions for determining the impact
of debris damming, which is the accumulation of debris between
columns of an open foundation, which results in an increased area
for the application of hydrodynamic loading.
Flood Load Factor
The last significant change is the reduction of load factors used in
load combinations that include flood. The LRFD flood load factor
has been reduced from 2.0 in V Zones and Coastal A Zones to 1.0
for all zones; the ASD load factor has been reduced from 1.5 in
V Zones and Coastal A Zones, to 0.70 for all zones. These reduc-
tions are possible because of the use of a higher return period for
the design flood; the resulting loads on structural elements now
achieve the target reliabilities assigned in ASCE 7 for each of the
Risk Categories.
Summary
There are a lot of changes to ASCE 7 Chapter 5, and after years
of minimal changes, it will likely take some time for the prac-
tice to incorporate all these changes into their designs. The new
chapter is published in ASCE 7-22 Supplement 2 and is available
for free download on the ASCE website. The recently published
Building Designer’s Guide to Calculating Flood Loads Using ASCE
7-22 Supplement 2 by FEMA walks users through several examples
and is also available for free download. FEMA continues to work
on a Future of Flood Risk dataset and user tool so that in the future
designers will be able to retrieve flood hazard data for various MRIs
and risk probabilities. The changes to flood design that are now
in ASCE 7-22, Supplement 2, should significantly strengthen the
flood load resistance for structures designed to these new provisions.
Figure 2. Numerical Simulation Results from USACE for Galveston, TX.
(Source: ASCE 7-22, S2, Chapter 5 Commentary)
Figure 3. Normally incident wave pressures on an elevated wall. (Source: ASCE 7-22, S2)

56. STRUCTURE magazine 56
Balustrade Design Loads: Failures, Fatalities,
Research & Global Design Practices
This article reviews global balustrade practices and how one can specify a project to meet best practices to
keep occupants safe.
By Richard Green, SE, PE, P.Eng.,CPEng, IntPE
codes & STANDARDS
I
n general, global building/loading codes are in close agreement
for most loading types, with variations of +/- 20% for comparable
conditions. However, the loads for handrails, barriers, and guards in
the United States (ASCE 7, IBC, ASTM E985 and ASTM 2358,
NAAMM AMP 521-01 et.al.) do not currently reflect values for
crowds and assembly areas that are in widespread use elsewhere in
the world, in particular Canada (NBC), Europe (EN), the UK (BS),
Brazil (ABNT) and Australasia (AS/NZS).
Comparison of the loads for typical cases, without assembly or crowd
loading, have good agreement with the 50 pounds force/foot (lbf/ft)
(0.73 kilonewtons/meter (kN/m) versus the 51.5 lbf/ft (0.75kN/m)
distributed loads; however, for crowd and stadium loadings, ASCE
7 and IBC have no additional requirements, whereas NBC, EN,
BS, ABNT and AS/NZS require 3 kN/m (~200 lbf/ft) for stadiums.
Additionally, EN, BS and AS/NZS also have an intermediate level of
1.5 kN/m (~103 lbf/ft) for specific areas of assembly, but this is not in
the NBC code. In total, of 45 countries in which balustrade loadings
were able to be found at the time of submission: 40 countries have a
maximum crowd loading of 3 kN/m (~206 lbf/ft) or greater (>4x U.S.
code loading), one country (India) has a loading of 2.25 kN/m (~154
lbf/ft) (~3x the U.S. code loading) and none have a lower loading.
A historical study of U.S. documents pertaining to loading
yields three main references: ASTM International ’s ASTM E985
Standard Specification for Permanent Metal Railing Systems for
Buildings, the American Society of Civil Engineers’/Structural
Engineering Institute’s ASCE/SEI 7 Minimum Design Loads
and Associated Criteria for Buildings and Other Structures, and
the International Building Code. Significantly, ASTM E985 was
originally released in 1984 and its references include Australian
Standard AS 1170.1 Structural design actions, Part 1: Permanent,
imposed and other actions, and British Standard BS6399 Loading
for buildings – Code of practice for dead and imposed loads
which at the time also showed 0.75 kN/m (~51 lbf/ft), but the
last technical update to E985 was in 2000, and it was withdrawn
from 2012 through 2024. (ASTM E985 was recently reinstated,
ostensibly as it was in 2000, for the purpose of bringing it up to
date.) Crowd and assembly loadings were adopted by BS6399
in 1996, AS/NZS 1170.1 in 2002 and EN1991 Eurocode 1:
Actions on structures—Part 1-1: General actions—Densities,
self-weight, imposed loads for buildings in 2002. In the interim
period, without maintenance of standards in the U.S., balustrade
loadings have languished; thus the question becomes: “Why did
they change elsewhere, and are those changes justified?”
The balustrade load categories proposed here were introduced in
BS6399 – 1996. The history of its introduction is unknown to the
author; however, it was possibly a reaction to the 1989 Hillsborough
Disaster (UK) where 96 people died in conditions of overcrowding,
following a collapse of a crowd barrier at an FA Cup semi-final soccer
Hundreds of crowded events have led to fatalities due to crowd crushing, some of which are the result of barrier collapse. However, codes for guardrails vary globally.

57. AUGUST 2024 57
match. The investigation listed several other precedent collapses.
Railing collapses have also been reported at a Philadelphia (PA, USA)
stadium in 1998, in Maryland (USA) in 2022, and at the Public
University of El Alto in Bolivia in 2021, which resulted in at least six
deaths and multiple injuries. The latter item is relevant as the Bolivian
loading standard for Actions on Structures (NB 1225002-1) requires
1.0 kN/m (69 lbf/ft), which is greater than the maximum balustrade
loading in ASCE 7/IBC/ASTM E985.
Other collapses without serious injury included events at NFL
football games. These are significant because there was not a great
depth of people pressing behind the barriers.
The Hillsborogh Disaster was thoroughly investigated and is well
documented by R.A. Smith from University of Sheffield in “The
Hillsborough Football Disaster: Stress Analysis and Design Codes
for Crush Barriers,” published in Engineering Failure Analysis (1994).
In the paper, Smith quotes the investigation report by Lord Taylor,
noting that similar investigations had occurred in 1924, 1946 (33
deaths), 1972 (66 deaths), and 1986 (56 deaths). Smith (writing
in 1994) also noted other crowd crushing events in 1990 (Mecca,
1,426 deaths), 1991 (Shanghai, 105 deaths) and 1992 (Madras,
65 deaths). The Wikipedia page https://en.wikipedia.org/wiki/
List_of_fatal_crowd_crushes#21st_century summarizes hundreds
of events and thousands of deaths due to crowd crushing. While
all of these do not include details of barrier collapse, they demon-
strate that fatal crowd loading is sufficiently frequent to be a design
consideration; we know that if a barrier collapses it is more likely to
cause crowd collapse and fatalities. It is important to prevent crowd
loading situations from turning into fatal ones.
In a report “Going Off the Rails” (2021), The National Center
for Spectator Sports Safety and Security (NCS
4
at the University of
Southern Mississippi) notes a history of fatalities and serious injuries
at U.S. sporting arenas, both old and new.
Design Loading for Barriers
While the Hillsborough Disaster was attributed in part to over-
crowding, post-failure analysis indicated that the railing failed at
approximately 8 kN/m; thus, the proposed loads of 3 kN/m (~200
lbf/ft) for crowd loading and 1.5 kN/m (~100 lbf/ft) for assembly
spaces is not excessive for reasonable design load situations. The El
Alto incident reinforces that elevated rail loading exceeding 1kN/m
(69 lbf/ft) is possible at assembly areas other than at stadiums, so the
approach in AS/NZS and EN, which is broader than in NBC, is justi-
fied. Eurocode includes a range of 3-5 kN/m (~200 lbf/ft – 340 lbf/ft)
with 3 kN/m (~200 lbf/ft) recommended. This approach highlights
some circumstances in which the designer may wish to select a load-
ing greater than 3 kN/m (~200 lbf/ft) if it is considered appropriate.
R.A. Smith includes the formulation of a “leaning crowd” model
used to estimate loads generated on a barrier on a stadium with ter-
raced seating.
Studies of crowd crushing by Fruin (1993) indicated that crush
forces of up to 3430 N (766 lbs) can be applied to a single person in
overcrowding situations; hence, similar loads should be anticipated
at barriers that contain crowds. This is important because the col-
lapse of a barrier can lead to people falling over an edge, or by falling
down and being crushed by those that land on top of them (Fried
and Grant JASM Venue Safety Strategies, 2023).
An animation at CrowdRisks.com/research.html provides a computer
simulation of “crowd collapse,” a situation in which a disturbance
causes one person to fall and be unable to shift and regain bal-
ance without pressing on the person next to them, who is then also
pushed off balance, creating a domino effect—with increasing mass
and synchronous dynamic effect and/or multi-cyclic impact as the
wave passes through the crowd. Review of the video of the El Alto
incident indicates that there were “pressure waves” within the crowd
Handrail, Top Rail, and
Guards
Infill
Handrail and
Guard Design
Category
OccupancyUse Examples Concentrated
Load lbf
(kN)
Uniform
Load
lbf/ft
(kN/m)
Concentrated
Load lbf (kN)
Uniform
Load psf
(kPa)
A Light dutyInterior
residential
and access
gantries
One and two family dwellings excluding external balconies
and edges of roofs, and; safe working places and access
normally used by operating, inspection, maintenance, and
servicing personnel with an occupancy of less than 50.
135**(0.6)25
(0.38)
50* (0.22)10*
(0.5)
B Basic Areas not
subject to
assembly or
overcrowding
Areas not susceptible to overcrowding: external residential,
office and institutional buildings, also industrial and storage
buildings.
200 (0.9)50
(0.75)
50 (0.22) 10
(0.48)
C AssemblyAreas where
assembly and
congrega-
tion may be
anticipated
All retail areas including public areas of banks/credit
unions; Areas with fixed seating adjacent to a balustrade,
restaurants, bars, etc. (See also D for areas where over-
crowding may occur)
200 (0.9)100
(1.5)
100 (0.45)20
(0.96)
D Crowd Areas
susceptible to
overcrowding.
Theaters, cinemas, grandstands, discotheques, bars, audito-
ria, shopping malls (see also C), assembly areas, schools,
universities, studios, etc.
300 (1.5)200 (3)200 (0.9) 30
(1.44)
Table 1. Summary of Handrail and Guard Design Categories per AS/NZS1170.1 and EN1991
With Rounding to Convenient Imperial Numbers.
* Actual value in AS/NZS and EN is 0.25kN = 56lbf; the current value in ASCE 7 is proposed for convenience.
** Value summarizes AS/NZS and EN but does not comply with OSHA 1910.28.

58. STRUCTURE magazine 58
Richard Green is the Founding Principal of Green Facades. He has over 30 years'
experience designing and engineering facade systems and specialty structures. He has
participated in building standards committees in Australia, United States, Europe and ISO
with a specialization on structural use of glass in buildings. (Richard@GreenFacadesLLC)
and that a scuffle added a dynamic component to the static load at
the time of collapse.
An Australian Study by C.T. Styan, M.J. Masia, and P.W. Kleeman
“Human Loadings on Handrails” in the Australian Journal of Structural
Engineering takes an experimental approach to measuring the horizontal
loads possible on rails and finds that the loads in the BS, EN, and AS/
NZ standards are reasonable and that in a significant number of cases,
exceed the loads in ASCE 7. The Australian study also documents
other failures due to overloading in the introduction to their study. In
the 1998 Philadelphia barrier collapse professional reports stated that
the failure was due to overloading, not a design fault (relative to the
design loading) and further notes that the audience was only one or two
rows deep. The test simulated loadings associated with various types of
occupancy and compared them with the design loading. Testing found
that a single row of people could generate static loads of 1.43 kN/m
(98 lbf/ft), two rows generated 2.12 kN/m (145 lbf/ft) and three rows
generated 2.66 kN/m (182 lbf/ft); adding dynamic “bouncing” and
a single row at the barrier generated 2.43kN/m (167 lbf/ft). In each
case, test results showed the design loads were appropriate; the results
also found that in circumstances subject to “unruly behavior,” such as
kicking the barrier, loadings higher than the design loading were pos-
sible. The testing also confirmed a 1.5 kN/m (~100 lbf/ft) loading for
an occupancy with assembly but without crowd loading.
Proposed Loading for Balustrades
As the occupancy categories used in the U.S. are different than
in the other standards referenced, the tables in BS, AS/NZS and
EN have been grouped and summarized by load. Notably, in Table
1 Category “A” there is a reduced point load relative to ASCE 7
for interior single residential usage, but a 25 lbf/ft uniform load is
required where ASCE 7 would exclude a requirement. The loading in
the U.S. is concentrated load based on a “grab load” and “soft body
slip impact load” as investigated by ANSI; hence, reductions are not
proposed, and the table is a conservative bounding of the criteria.
Additionally, concentrated loads do not match the 200 lbf point load
requirements in the Occupational Safety and Health Administration
(OSHA) Regulations 1910.28.
The proposed design loads in Table 1 are an amalgamation of the
referenced EN and AS/NZS standards and the existing precedence
in ASCE 7. The load categories do not align directly between the
standards; whereas ASCE 7 has concentrated loads for the top rail
and the components, and a uniform load for the top rail, the AS/
NZS standard has all of these, and a distributed load applied to infill
panels. The EN/BS standards have a concentrated load applied to the
infill only (albeit that this is similar to or greater in magnitude than
the ASCE 7 concentrated loads for top rails.) The reference standards’
inclusion of distributed loads applied to infill components is incor-
porated in the recommendation as it is likely important for barrier
walls and fences. Canada’s National Building Code has incorporated
allowances of 0.5 kPa (~10 psf) for walls as barriers.
Factors of Safety at the Anchors
ASTM E985 continues to be referenced and was recently reinstated in
its prior form so that it can be updated. As such, it is noteworthy that
not only does it not recognize assembly or crowd loading, it regards
the 50 lb/ft as a test load for both the balustrade system and the attach-
ments to structure as tested in ASTM E894 Test Method for Anchorage
of Permanent Metal Railing Systems and Rails for Buildings and E935 Test
Methods for Performance of Permanent Metal Railing Systems and Rails for
Buildings. Such testing protocols do not currently allow any variability
in the materials or testing to provide a safety factor. For example, the
National Design Specification (NDS) for wood recommends a safety
factor of 5 for withdrawal of fasteners relative to test data to allow
for system variation. For post-installed concrete anchors under static
loading a factor of safety of 4 is common but is greater for dynamic
loading. Post-installed concrete anchors should pass the requirements
of American Concrete Institutes’ ACI 355.2 Qualification of Post-
Installed Mechanical Anchors in Concrete and Commentary. As noted
in a report “Going off the Rails” by The National Center for Spectator
Sports Safety and Security, where railings fail, failures at the anchors are
the most common cause. The Australian Standard 1170.0 Structural
design actions, Part 0: General Principles Appendix B provides proof
load testing factors based on sample size and coefficients of variation.
Following ASTM methods, the combination of lack of crowd loading
and safety factor for testing results in metal railing systems attached
to a wood structure, tested and approved to ASTM E985 and E935,
are one fifteenth of the loads prescribed by AS1170.1 and testing to
AS1170.0 Appendix B . Even for the current ASCE 7 design loads, the
lack of a safety factor in testing means that systems approved by testing
potentially have a significantly lower strength than systems justified by
calculation to the relevant materials standards.
Conclusion
The proposed loads in Table 1 are reasonable and validated. The
reference in Eurocode EN 1991 indicates a range of crowd loads
between 3 kN/m (~ 200 lb/ft) and 5 kN/m (~ 340 lb/ft) and the
post-failure analysis of the Hillsborough barriers indicated failure at
~8 kN/m (~ 550 lbf/ft); however, the latter was in a case of extreme
overcrowding which might be considered greater than a reasonable
design case. Crowd loading of 3 kN/m (~ 200 lb/ft) has also been
adopted by the Canadian code for stadiums.
Justification by testing to meet standards needs to incorporate suit-
able safety factors based on the materials they are being attached to
as well as testing variations. For testing with samples of 6 or more, a
proof load factor of 2.5x for steel, 4x for concrete, and 5x for wood
is consistent with achieving statistical significance consistent with the
respective materials’ standards and coefficient of variation.
There is a large discrepancy between balustrade loadings in the United
States and most other countries. Changes elsewhere were based on
multiple disasters, investigation of those events, and validation by
testing. The balustrade loads similar to Table 1 have been adopted
in over 40 counties. These loads have been proposed to ASTM and
ASCE for future incorporation. In the interim, design professionals
and project specifiers have the option to follow international best
practice when selecting appropriate testing and design loads for
balustrades and guards.
Full references are included in the online version of the article
at STRUCTUREmag.org.

59. AUGUST 2024 59
The Gold Standard in Steel Design
The 16th Edition AISC Steel Construction Manual marks nearly 100 years in publication.
By Margaret Matthew, PE, and Yasmin Chaudhry, PE
codes & STANDARDS
A
ISC recently released the 16th Edition
Steel Construction Manual. The 16th
edition celebrates nearly a century of pub-
lishing one of the most respected design
aids in the construction industry.
The big changes in this edition are outlined
here. While not everything new is mentioned
here, a full list of changes and updates are
included in the Preface to the 16th edition.
Dedication
The AISC Committee on Manuals has
dedicated the 16th edition to Dr. William
(Bill) A. Thornton, former Chairman and long-
time member of the committee. From 1985
until 2011, Bill served as the Chairman of the
Committee on Manuals and oversaw the develop-
ment of numerous Manual editions, including
the First edition LRFD Manual and the 14th
edition Manual. The 16th edition is only the
second Manual ever to be dedicated and honors
Bill’s many contributions to the industry.
Big Changes in Materials
The big story in the 16th edition starts in Part 2, General Design
Considerations, which includes a wide range of guidance applicable
to the design and construction of steel buildings. Significant changes
were made to the tables that help guide users when specifying material:
Table 2-4 includes the available grades of standard structural shapes,
Table 2-5 includes available grades of plate and bar material, and
Table 2-6 includes available grades of structural fasteners.
In addition to available material grades, the tables show preferred grades
for different components. For every new Manual, AISC reviews the
materials that are commonly used in steel construction to develop a list
of preferred materials that reflect factors like ready availability, ease of
ordering and delivery, and pricing. The use of preferred materials will
help avoid material procurement issues and the potential for added cost.
An important distinction—preferred does not mean required. Any
of the other applicable material specifications can be used successfully
on a project, but the availability and cost-effectiveness of grades other
than the preferred material specification should be confirmed with a
fabricator prior to their specification.
Here are the major changes in the tables:
• The preferred material specification for M-, S-, and L-shapes has
been updated to ASTM A572/A572M Grade 50 from ASTM
A36/A36M.
• The preferred material specification for C- and MC-shapes has
been updated to ASTM A992/A992M from ASTM A36/A36M.
• The preferred material specification for round HSS is still ASTM
A500/A500M Grade C, however the yield strength has increased
from 46 ksi to 50 ksi.
• The preferred material for plates and bars up to 4 in. thick has
been updated to ASTM A572/A572M Grade 50 from a dual
preference of ASTM A572/A572M Grade 50 and ASTM A36/
A36M. There is now a row in Table 2-5 listing ASTM A36/
A36M as a preferred material specification for “All other applica-
tions.” This row is for elements like toe-kicks, edge plates, and
other miscellaneous steel where the additional yield strength
of A572 Grade 50 is not necessary.
Updated Connection Materials
All shear connection design tables found in Part 10 have been
updated from 36 ksi to 50 ksi connection material. Designers can use
the tables to aid the design of typical shear connections using higher
strength materials that are regularly used today.
The 2022 AISC Specification and 2020 RCSC Specification have
adopted a new bolt specification, ASTM F3148. This new bolt grade
has a tensile stress of 144 ksi, which puts its strength between Group
120 and Group 150 bolts. These new Group 144 bolts are an option
in the shear connection tables throughout Part 10.
Big Changes to Shear Connection Table Format
The Part 10 shear connection tables received a major revamp. The
tables affected are:
16th Edition of the AISC Steel
Construction Manual
Dr. WIlliam A. Thornton
Standard Year
AISC Specification for Structural Steel Buildings (ANSI/
AISC 360-22)
2022
AISC Code of Standard Practice for Steel Buildings
and Bridges (ANSI/AISC 303-22)
2022
RCSC Specification for Structural Joints using High-
Strength Bolts
2020
Minimum Design Loads and Associated Criteria for
Buildings and Other Structures (ASCE/SEI 7-22)
2022
AWS D1.1/D1.1M Structural Welding Code—Steel2020
ASTM A6/A6M Standard Specification for General
Requirements for Rolled Structural Steel Bars, Plates,
Shapes, and Sheet Piling
2019
New Codes and Standards

60. STRUCTURE magazine 60
• Table 10-1—All-bolted double-angle connections
• Table 10-4—Shear end-plate connections
• Table 10-10—Single-plate connections
• Table 10-12—Bolted/welded single-angle connections
Each of these tables is split into three subtables—one to verify the
connection material strength, one to verify the shear transfer strength at
the bolt holes, and one to verify the strength of the supported member
when coped. The new tables will allow for an easier determination of
the effective bolt shear transfer strength and the shear strength of the
supported beam web when coped. See Table 10-1a in Figure 1.
Other Changes of Note
New Guidance for Corrosion Protection
Part 2 of the 16th edition includes expanded guidance for corrosion
protection. A new section on galvanic corrosion was added to help
identify situations where galvanic corrosion may be an issue when
joining dissimilar metals. The new section lists conditions where gal-
vanic corrosion is unlikely and where risk is high. A new table, Table
2-8 shown in Figure 2, provides a matrix of common construction
metals and their steady state electrode potential as a basis to identify
the potential for galvanic corrosion.
Manual Resources
The 16th Edition Manual is not all that’s new. Accompanying its
release are several useful, free resources available at
www.aisc.org/manualresources.
The Manual Companion
The new version 16.0 Companion to the AISC
Steel Construction Manual is a two-volume set
containing nearly 1,800 pages of material to
supplement the Manual.
Manual Companion, Volume 1: Design
Examples v16.0 includes more than 160
complete design examples illustrating
commonly used provisions in the 2022 AISC
Specification and the16th edition Manual
for designing members, connections, and
structural systems.
The v16.0 Manual Companion, Volume 2: Design Tables, contains
20 design tables that supplement the Manual with additional
material grades, including ASTM A913 Grades 65 and 70
W-shapes and ASTM A1085 HSS members.
AISC Shapes Database and Historic Shapes Database
The v16.0 Shapes Database is a Microsoft Excel spreadsheet that
compiles the dimensions and properties of all shapes printed in
Part 1 of the Manual.
The new v16.0H Historic Shapes Database is updated with
all dimensions and properties consistent with the 15th edition
Manual. This resource provides a complete list of historical shape
information recorded from 1873 to 2016.
Basic Design Values Cards
The Basic Design Values Cards are a set of pocket-sized cards
presenting some frequently used limit state equations for checking
members and connections from the 2022 Specification in an
abbreviated format.
Interactive Reference List
The Interactive Reference List is a complete listing of all the
references found in both the 2022 Specification and 16th Edition
Manual. Many of the references are available from the AISC
website, while others are linked to the outside organization where
the listed publication can be accessed or purchased.
Fig. 1 (left). New tables, such as Table 10-1a allow for easier determination of the effective
bolt shear transfer strength. Fig. 2 (above). This new table provides a matrix of common
construction metals and their steady state electrode potential.

61. AUGUST 2024 61
Margaret Matthew ([email protected]) is the AISC Director of Manuals. Yasmin
Chaudhry ([email protected]) is a senior engineer in the AISC Steel Solutions Center.
Interpolation, Stability, and More
Additional changes in Part 2 includes a new section, Using the Manual
Tables, that alerts users about interpolation within design tables, and
a section on Simplified Determination of Required Strength that
presents a simplification of the effective length method when a quick,
conservative solution is desired.
When preparing contract documents, start with the updated section
on Contract Document Information, which summarizes the require-
ments from the AISC Specification, the AISC Seismic Provisions, and
the AISC Code of Standard Practice.
Structural Analysis Benchmark Solution
Solutions for a first- and second-order analysis of two beam-columns
are now provided in Part 6. The new Table 6-5, shown in Figure 3,
conveniently includes benchmark solutions for bending moments and
deflections of a simply supported beam subjected to an axial load and
transverse uniform load (Case 1), and a cantilevered member subjected
to an axial force and transverse point load (Case 2).
These solutions are intended to validate solutions from computerized
structural analysis or facilitate computation of required forces and
deflections during design when the member configuration matches
the given configurations.
Consolidation of Moment Connection Parts
Part 11, which in previous editions contained information for partially
restrained (PR) moment connections, and Part 12, which included
information for the design of fully restrained (FR) moment connec-
tions have been merged into the new Part 11, Moment Connections.
New Design of Simple Connections for Combined Forces
The new Part 12, Design of Simple Connections for Combined Forces,
provides guidance on the design of typical shear connections subjected
to axial or torsion forces in addition to shear forces.
New Bracing Connection Discussion
Part 13, Design of Bracing Connections and Truss Connections, has
several updates in the 16th edition. The Uniform Force Method has
been expanded with a new “Special Case 4” that utilizes a single plate
at the column connections. The new special case is useful where braces
framing into the column web can create erection difficulties in the field,
especially when columns have stiffener (continuity) plates in the web.
Part 13 also includes a new section covering chevron bracing connec-
tions, which require special consideration during both member and
connection design due to a phenomenon called the “Chevron Effect.”
Lastly, Part 13 includes new material covering the design of horizontal
bracing connections.
New Table for Coped W-Shapes
Part 9, Design of Connecting Elements, contains a new “Plastic
Section Modulus for Coped W-Shapes” table as a companion to the
coped beam elastic section modulus table in previous editions. The
procedure for checking the available flexural strength of a beam with
a cope at the top flange provided in Part 9 requires the calculation of
the plastic bending moment of the coped section. This calculation is
much simpler now using the coped beam plastic section modulus taken
directly from the new table.
Increased Weld Strength for Double-Angle Connections
Tables 10-2 and 10-3 are used for the design of bolted/welded or all
welded double-angle connections. For the weld between the angles and
the support (“Welds B”), the weld design method was changed from the
elastic method to the instantaneous center of rotation method. The updated
design method will provide higher connection strengths. Additionally, these
tables have a new weld geometry (“Welds C”) that includes additional
lines of weld at the bottom of the angles, providing additional connection
strength where needed.
The new Manual can be purchased at www.aisc.org/16thedition.
Fig. 3. The new Table 6-5 includes benchmark solutions for bending moments and
deflections of two beam-column examples.
Fig. 4. Part 13 includes new material covering the design of horizontal bracing connections.

62. STRUCTURE magazine 62
University of Florida Wins 2024 Student
Steel Bridge Competition
industry NEWS
S
tudent engineers from the University of
Florida secured their fourth straight first-
place overall win in the 2024 Student Steel
Bridge Competition (SSBC) National Finals
on June 1, breaking the consecutive titles
record they set themselves in 2023.
Louisiana Tech University in Ruston,
LA, served as the host school for the 2024
competition.
This year’s SSBC participants were chal-
lenged to design, fabricate, and quickly
construct a scale-model steel bridge that
would span a man-made river in a large
disc golf course. Competitors had to find
innovative ways to navigate new rules and
challenging assembly constraints, including
one of the widest conceptual rivers in the
competition’s history.
In addition to winning the overall prize (and
$5,000 in scholarships), the University of
Florida placed first in economy and light-
ness and came in second for efficiency. They
achieved an 11-minute, 37-second assembly
O’Donnell & Naccarato Celebrates
Opening of Broad + Noble Apartments
O
’Donnell & Naccarato (O&N), a structural engineering firm head-
quartered in Philadelphia, celebrated the grand opening of Broad +
Noble, a luxury apartment tower in Center City, PA. With views of the
city skyline, the 19-story, 326,000-square-foot residential high rise offers
top-of-the-line amenity spaces, as well as a blend of retail and office space
and secure below-ground parking.
O&N provided structural engineering services for the $112 million
project, in partnership with developer Toll Brothers Apartment Living
and architect Barton Partners. The building, which broke ground in
2021, features a traditional brick exterior in a nod to the historic industrial
architecture of Philadelphia’s Callowhill neighborhood and overlooks a
sprawling landscaped plaza with a separate, two-story retail space, nestled
between its massive L-shaped footprint.
Residents of the 344-unit apartment complex will also enjoy a sky
lounge with private dining, outdoor terraces, and a rooftop deck created
by setbacks at the building’s upper levels.
Broad + Noble is constructed almost exclusively with 8-inch precast
plank floors, using the Girder-Slab structural system to maximize
space relative to the building’s height. The top-floor sky lounge is
designed with a plank floor system on steel wide-flange beams, and
large steel transfer beams interrupt the spacing of columns and highly
coordinated brace frames within the residential floors to permit a
transition to amenity spaces and below-grade parking on the first
and second floors below.

63. AUGUST 2024 63
time with only two builders.
“I was nervous coming into the main com-
petition,” said Anthony Perez Ortegon,
co-captain of the University of Florida steel
bridge team. “These teams spent just as much
time–if not more–as we did, putting in so
much work. Seeing their bridges and how
much they love them really puts this pres-
sure on you that’s like, ‘man, they brought
the competition.’”
University at Buffalo came in second overall,
winning second place in construction speed
and third place in economy—plus $3,000 in
scholarship funds.
Lafayette College won third place overall
and brought home $2,000 in scholarship
support. They received the Frank J. Hatfield
Ingenuity Award, which recognizes innovative
approaches to competition rules. Lafayette’s
student engineers took advantage of a new
SSBC rule requiring the use of rigid contain-
ers for loose nuts and bolts by wearing the
containers on their arms for efficient access
to the bolts.
“All 47 teams impressed us with their creativ-
ity, willingness to compete, and togetherness,”
said AISC President Charles J. Carter, SE,
PE, PhD. “They made it such a wonderful
weekend for all of us.”
The final results of the 2024 competition
are as follows:
Overall
University of Florida
University at Buffalo
Lafayette College
Construction Speed
William Jewell College (0:4:30)
University at Buffalo (0:6:06)
University of California, Davis (0:6:22)
Lightness
University of Florida
Liberty University
University of Connecticut
Aesthetics
Virginia Tech
University of Michigan
University of Texas at Tyler, Houston
Engineering Center
Stiffness
University of Wisconsin, Platteville
University of Alaska, Fairbanks
University of California, San Diego
Cost Estimate
University of Texas at Tyler, Houston
Engineering Center
University of Connecticut
Pennsylvania State University, University Park
Economy
University of Florida
William Jewell College
University at Buffalo
Efficiency
University of Alaska, Fairbanks
University of Florida
University of Wisconsin, Platteville
Team Engagement Award
University of Nevada, Las Vegas
Robert E. Shaw Jr. Spirit of the
Competition Award
South Dakota School of Mines and
Technology
Frank J. Hatfield Ingenuity Award
Lafayette College
John M. Yadlosky Most Improved
Team Award
Arizona State University
Video Awards
University of British Columbia
Universidad Nacional Autónoma de México
University of North Carolina at Charlotte
The SSBC planning committee also
announced that Iowa State University is the
official host of the 2025 SSBC National Finals
(May 30-31, 2025, in Ames, IA).

NIST Engineers
Finalists for Samuel
J. Heyman Service
to America Medal
N
IST announced two of its own are finalists for the Samuael J.
Heyman Service to America Medal for their work on tornados
and designing structures that can withstand them. Long Phan and
Marc Levitan have "played a critical role in changing minds about
designing for tornadoes by conducting groundbreaking research and
advocating for changes to building codes and standards," according
to a post on NIST's Taking Measure blog.
The Samuel J. Heyman Service to America Medals are given to career
federal employees and chosen through a selection process led by a
panel of leaders in academia, business, philanthropy, government,
and media. Winners will be announced in the early fall.
"In 1997, a big tornado hit Jarrell, Texas.
At the time, the National Weather Service rated
tornadoes using the Fujita scale. The Fujita scale
estimates tornado wind speed by assessing the
damage it caused. It assumes that more damage
means there was a higher wind speed. The
Jarrell tornado was rated as an F5, the highest
possible Fujita rating.
As a structural engineer with experience in
structural failure, when I looked at the Jarrell
tornado, I just didn’t think that the damage was
necessarily caused by extremely high wind
speed. So, I began to think, 'OK, the Fujita scale
might not be accurate.'" —Long Phan as told to
NIST's Taking Measure Blog.
Long Phan 
Marc Levitan

64. STRUCTURE magazine 64
HGE Launches
Chicago Studio
H
atfield Group Engineering (HGE), a New York-based, WBE-
certified, multidisciplinary engineering firm, announced the
launch of its Chicago studio. HGE Chicago is led by Koz Sowlat, SE,
PE, and Robert J. Diebold, SE, PE, who have co-led their firm, Sowlat
Structural Engineers, since its founding in 2004. HGE Chicago was
established on May 4, 2024, to better serve HGE clients, by leverag-
ing Sowlat and Diebold’s structural expertise, and by bringing HGE’s
structural, MEP/FP, and facade engineering services to the Midwest.
Sowlat, Diebold, and HGE founding partner, Erleen Hatfield,
PE, FAIA, F. ASCE, worked together while at Perkins and Will and
Thornton Tomasetti and are reunited to provide their expertise in the
design of large, complex buildings with fast-track schedules, leading
to high-quality built projects.
HGE Chicago is currently delivering structural engineering services
for the following projects:
• The Lake View, 333 Superior Street, Duluth, MN, a 16-story
residential building, under construction
• Hilton Chicago Renovations, Chicago, under construction
• The Chicago Housing Authority, North Lawndale Building
Renovations, Chicago
• 424 South Wabash, Chicago, a 26-story Sonder Hotel.
Construction is underway on the University of Michigan's College of Pharmacy building. The
project, designed by RDG Planning & Design alongside Alvine Engineering (mechanical,
electrical and plumbing), TD2 Engineering & Surveying (structural engineering) and
Midwestern Consulting (civil engineering), is utilizing mass-timber structures to reduce
greenhouse gas emissions, increase the speed of construction and provide well-being benefits.
RDG’s design combines fire detection and suppression systems that go beyond baseline fire
codes and standards to further improve fire performance. Plus, mass timber enhances fire safety
by creating a char layer on the surface of the wood that insulates and protects the inner core
from burning. The building is scheduled to be completed in the fall of 2025.
Univ. of MI Building
Using Mass Timber

65. AUGUST 2024 65
A
rchitecture and Engineering firm, IDOM, has com-
pleted a successful final design review for one of the
largest mechanized smart buildings in the world.
The Giant Magellan Telescope, which is now 40%
under construction and on track to be operational by
the early 2030s, is the work of the GMTO Corporation,
an international consortium of 14 universities and research
institutions representing the United States, Australia,
Brazil, Chile, Israel, South Korea, and Taiwan. The tele-
scope is being built in America and will be reassembled
and completed in Chile by the early 2030s.
Once completed, the 65-meter-tall enclosure will be
one of the largest mechanized buildings ever constructed
and will represent a true feat of modern engineering and
precision manufacturing. At over 5,000 metric tons, the
enclosure will be able to complete a full rotation in four
minutes and be equipped with 46-meter-tall shutter doors
that reveal the 25.4-meter telescope for unobstructed
scientific observations. The smart building is designed
to control the telescope’s operating environment by pro-
tecting seven of the world’s largest mirrors as they track
celestial objects across the sky more than a billion light
years away.
IDOM began developing the Giant Magellan Telescope
enclosure design over two years ago following a competi-
tive, global search and extensive evaluation process.
“Our team approached the challenge of the Giant
Magellan Telescope enclosure knowing that this struc-
ture would be responsible for enabling some of the most
important scientific discoveries of our lifetimes,” said
IDOM North American President Tom Lorentz. “We
are proud to have delivered a successful design and look
forward to the Giant Magellan Telescope’s success.”
With the enclosure design milestone complete, the Giant
Magellan Telescope is now preparing a global search for a
firm to leave their mark on the future of astronomy with
construction of the enclosure.
Giant Magellan Telescope Enclosure
Ready for Construction
Once completed, the 65-meter-tall enclosure will
be one of the largest mechanized buildings in the
world. Credit: Giant Magellan Telescope - GMTO
Corporation
Lockwood, Andrews &
Newnam Inc. Executives
Appointed to
ACEC Leadership Roles
Two leaders at Lockwood, Andrews &
Newnam, Inc. (LAN) have been appointed
to significant positions within the American
Council of Engineering Companies (ACEC)
state and local chapters. President Wayne
Swafford, PE, will serve as president-elect for
the 2024-2025 ACEC Texas Officers, and
Chief Operating Officer Steve Gilbreath,
PE, will serve as director for the 2024-2025
ACEC Houston Board of Directors. Swafford
and Gilbreath will bring their extensive
expertise and leadership to their respec-
tive roles.
Swafford, a structural engineer with more
than 30 years of experience, is responsi-
ble for the direction and operation of LAN.
Gilbreath currently serves as the chief oper-
ating officer of LAN, where he oversees the
firm’s day-to-day operations.
ACEC is the business voice of America’s
engineering and design services industry.
ACEC Texas is a statewide organization
representing over 300 member firms in the
engineering industry.
Test Labs Formerly Known as
ICC-NTA Now Operate as
ICC-ES Labs
To solidify ICC-ES as a one-stop-shop for
testing, inspection, and certification, ser-
vices offered by the ICC-NTA Building and
Plumbing Products division, including inspec-
tions, testing, and certification engineering,
are being branded as ICC-ES, effective
immediately.
The acquisition of NTA into the ICC Family
of Solutions in 2019 expanded the services
the Code Council provides by adding testing
and inspection capabilities. This addition
streamlines the technical evaluation process
provided by ICC-ES. Both teams working
together simplifies the process for clients as
verified resources can readily be shared
across companies, eliminating the need for
additional communication steps.
The company is working with the respective
accreditors to ensure a seamless transition
to the ICC-ES brand and with no disruption
to current report holders.
The ICC-NTA brand will remain associated
with off-site construction services, including
plan review, inspection and certification of
modular home systems.
Test laboratory locations span several
states to offer local testing options to cus-
tomers, from Texas to Indiana. For more
information and frequently asked questions,
visit www.icc-es.org.
IN BRIEF

66. NCSEA News News from the National Council of Structural Engineers Associations
STRUCTURE magazine 66
Arizona Bill Ensures Continuation of Board of
Technical Registration
Arizona lawmakers passed Bill HB2253, ensuring the continuation of the Arizona
Board of Technical Registration (BTR), with Governor Katie Hobbs signing it
into law on June 18. This decision ends the uncertainty that arose when the bill
stalled in the Senate, threatening the BTR’s existence beyond July 1, 2024.
The BTR regulates licensure, applications, renewals, complaints, and disciplinary
actions for structural engineers and other professionals in Arizona. Its continuation
is vital for maintaining high standards and protecting the health, safety, and welfare
of Arizona citizens. The passage of HB2253 ensures the BTR will continue its
crucial role in safeguarding public interests and upholding professional standards
in Arizona. Moreover, the preservation of the BTR underscores the importance
of professional regulation, which benefits structural engineers nationwide by
reinforcing the significance of rigorous licensure and regulatory oversight.
NCSEA, as part of the Structural Engineering Licensure Coalition with CASE
and SEI, supported the SEA of Arizona in advocating for the bill.
NCSEA Foundation Board President Tricia Ruby
Honored With Humanitarian Award
Tricia Ruby, President of the NCSEA Foundation Board, is the
recipient of the 2024 Horace H. Rackham Humanitarian Award from
the Engineering Society of Detroit (ESD). This prestigious accolade
recognizes outstanding humanitarian achievements through techni-
cal accomplishments or exceptional contributions to civic, business,
public-spirited, or humanitarian endeavors.
Ruby is a strong advocate for diversity and inclusion within the
engineering and construction industries. Her leadership roles in the
NCSEA Foundation and ACE Mentor Southeast Michigan highlight
her commitment to these causes. Her ded-
ication has earned her multiple awards,
including the AFP Distinguished Volunteer
Award and the ACEC National Community
Service Award. Ruby was presented with the
Rackham Award, ESD’s highest honor, at
the organization’s annual dinner on June 26.
The NCSEA Foundation recently announced the launch of the
“Structural Engineer Spotlight Series: Something From Nothing,” a
webinar series created by esteemed filmmaker Dilip Khatri. The series
showcases the remarkable journeys of members from the Structural
Engineers Association of Southern California (SEAOSC) as they rise
from humble beginnings to become influential figures in the field.
The series kicked off with Episode 1 on July 19, featuring Lorena
Arce, who shared her journey, struggles and achievements. Episode
2, airing on Aug. 16, will highlight Adena Geiger’s story of moving
from Iran, navigating a rigorous education process and earning her
master’s degree in civil engineering. It concludes with Episode 3 on
Sept. 20, featuring Daryl Frigillana’s path to becoming a structural
engineer. Each webinar will take place at 10 a.m. PT/12 p.m. CT/1
p.m. ET and will include a live Q&A with the featured engineer.
The webinar series is made possible by the NCSEA Foundation and
is complimentary to attend.
Free Webinar Series Spotlights Inspiring Structural Engineers
Tricia Ruby

67. NCSEA News News from the National Council of Structural Engineers Associations 67AUGUST 2024
Speed of Construction, Deferral of Repairs Top
List of Structural Engineers’ Concerns
September 12 New Buildings <$30: STRUCTURE OF THE YEAR WINNER:
Children’s Museum of Eau Claire
September 19 Significant Changes to ASCE 7-22 Supplement #2:
Chapter 5-Flood Loads
September 26 Forensic/Renovation/Retrofit/Rehabilitation Structures <$20 Million:
Sandi Simon Center for Dance at Chapman University
NCSEA Webinars
Purchase an NCSEA webinar subscription and get access to all the educational
content you’ll ever need! Subscribers receive access to a full year’s worth of
live NCSEA education webinars (25+) and a recorded library of
past webinars (170+) – all developed by leading experts;
available whenever, wherever you need them!
Recommendations for Performing Structural Engineering Quality Assurance Reviews
Visit www.ncsea.com/education for the latest news
on upcoming webinars and other virtual events.
NCSEA recently released results from its survey of structural engineers
about their biggest concerns for communities and the built environment.
Topping the list of concerns was the speed of construction projects (42
percent of respondents) followed closely by deferment of important struc-
tural improvements and repairs (41 percent of respondents).
“The increased pace of design and construction can pose challenges to
detailed coordination and project quality, but it also opens up new oppor-
tunities,” says Andrew Podojil, P.E., S.E., Associate at Veitas Engineers.
“Involving structural engineers early and expanding contracted scope allows
deeper collaboration; better risk management; and, ultimately, elevates
project outcomes. Also, discussing concerns with your engineer will better
serve the needs of the building owner and future occupants, leading to
improved overall quality and reduced construction costs.”
Structural engineers are dedicated to ensuring the stability and safety of
buildings and bridges in communities all over the world. Factors such as
site location, environmental conditions, building material characteristics,
and load demands all influence the structural design and are considered
from concept through completion of every project they are involved in.
After construction speed and lack of important improvements and repairs,
survey respondents (37 percent) indicated that aging infrastructure was
also a major area of concern.
“Investing in the rehabilitation and retrofit of existing buildings and
infrastructure may not be the easiest sell to decision makers, but these are
necessary investments for the safety and resilience of our communities,”
says Ed Quesenberry, S.E., Founding Principal of Equilibrium Engineers
LLC and NCSEA Past President. “Structural engineers have the knowledge
and tools to make these critical improvements as economically feasible
as possible.”
The survey was part of NCSEA’s We SEE Above and Beyond cam-
paign, which illustrates how structural engineers create safe, vibrant,
and resilient communities and provides valuable resources for archi-
tects and building owners.
Discover Best Practices in Building Assessments at
Preconference Symposium
Structural engineers attending the NCSEA 2024 Structural
Engineering Summit can kick off their experience with a special
preconference symposium on Nov. 5 in Las Vegas. “Existing Buildings
Assessments: Lessons Learned and Best Practices for Structural
Engineers” is a half-day event packed with valuable insights.
Attendees will learn about advanced investigation methods like
non-destructive testing, surveying, monitoring, and scanning. The
symposium will cover common structural failures in materials
such as steel, concrete, wood, and masonry, and building parts
like parking garages, balconies, and decks. There will also be tips
on report-writing, including rating systems, assessment levels, and
legal aspects. The symposium, sponsored by DEWALT, will award
4.75 PDHs to attendees.
The event is open to everyone, with a registration fee of $249 for
NCSEA members and $449 for non-members. You don’t need to
attend the full Summit to join this symposium. To sign up, create a
profile at NCSEASummit.com/register and select “Existing Buildings
Assessments” at checkout.

68. STRUCTURE magazine 68CASE in Point News of the Coalition of American Structural Engineers
Tools To Help Your Business Grow...
CASE has committees that work together to produce specific resources available to members, from contract
documents to whitepapers, to help your business succeed.
If you are a member of CASE, all CASE publications are free to you. NCSEA and SEI members receive a
discount on publications. Use discount code - NCSEASEI2022 when you check out.
Check out some of the new CASE Publications …
CASE Tool 2-8 – Making Remote Work Work
In today’s world, survey after survey has listed flexible work schedules and work location as a top desire of employees at all levels. Many
companies are currently struggling through this shift and trying to determine what works best for the company in the long term as there
are many pros, cons, and important considerations. In addition, structural engineering firms are having more difficulty filling positions
and expanding the candidate pool beyond the local office locations could yield high quality employees. These options do create business,
insurance, technical, IT/security, productivity, training/mentoring and cultural challenges. This Tool attempts to provide some guidance
in these areas.
CASE Tool 3-7 – Succession Planning
A critical component of talent management is succession planning. Training, development, career planning (employee-centered), career
management (organization-centered), and replacement planning are all key elements of succession planning. Successful succession planning
helps an organization cope with talent scarcity, identify skill gaps and training needs, promote knowledge transfer to retain institutional
knowledge, increase morale and retention by investing in employees, and create bench strength for unique and highly specialized skill sets.
CASE Tool 5-7 Best Practices for Use of Analysis and Design Software
This tool provides guidelines and tips for the verification of analysis and design software results. It focuses on linear elastic structures and
small deformation/small strain analysis which represent the vast majority of design office work.
CASE White Paper: Teaming Agreements
An important aspect of a joint project pursuit between a contractor or design professional and a structural engineer is an agreement
covering the activities of the parties prior to contract award. This agreement is commonly referred to as a teaming agreement. Teaming
agreements are often associated with design-build projects but can be used on any project pursued jointly by two or more parties. Many
organizations familiar to structural engineers provide a standard form teaming agreement. This commentary summarizes the contents and
typical clauses of the standard form teaming agreements offered by these four organizations:
• American Institute of Architects (AIA): Contract C102-2015
• Engineers Joint Contract Documents Committee (EJCDC): Contracts D-580 and E-580
• Design-Build Institute of America (DBIA): Contract No. 580
• Consensus Docs: Contract Nos. 296 and 498.
You can purchase these and other Risk Management Tools at
https://www.acec.org/member-center/get-involved/coalitions/case/resources/
Is there something missing for your business practice? CASE is committed to publishing the right tools for you.
Have an idea? We’d love to hear from you!

69. 69CASE in Point News of the Coalition of American Structural Engineers
Now more than ever we need to support the upcoming generation
of the workforce.
Give to the CASE Scholarship today!
AUGUST 2024
Upcoming Events
CASE Summer Meeting
August 8-9, 2024, Minneapolis, Minnesota
The CASE Summer Meeting will be in Minneapolis, Minnesota this year. The meeting will feature break-
out sessions for the CASE Committees, interactive discussions on structural engineering and business
resources, education sessions, and more. Registration is open now.
https://www.acec.org/event/case-summer-meeting/

70. STRUCTURE magazine 70SEI Update News of the Structural Engineering Institute of ASCE
The past year has been transformative for the Professional Community
(PC) in SEI, marked by growth and exciting new procedures. Under the
leadership of its dedicated executive committee, the PC has navigated
the shifting landscape of the SEI reorganization, leveraging the collective
expertise of its subcommittees to drive meaningful progress. Current
Chair Nicole Baer P.E., F. SEI., M. ASCE., emphasizes the PC’s pivotal
role in disseminating knowledge and nurturing future leaders, stating,
“The way I was kind of looking at it is the technical community creates
content, but the professional community is the one that gets that content
out to the world.”
A significant development this year has been the ongoing global initia-
tives within the PC. These initiatives, including the establishment of
Interorganizational Collaboration Committee, represent a major expansion
of the PC’s reach and impact. The goal is to foster strong connections and
collaborations with structural engineers worldwide, promoting cooperation
and knowledge exchange. Currently, the committee is undergoing a name
change and will be calling for new members who are passionate about
forging global partnerships and driving innovative projects.
The PC ExCom has introduced several operational enhancements to
improve communication and collaboration among the committees and
graduate student chapters. By assigning liaisons to each committee, the
ExCom ensures that these groups stay connected, share progress, and
collaborate effectively.
Vice-Chair Trevor Walker P.E., S.E, M. ASCE., highlights, “I’ve been
very pleasantly surprised at how much appreciation there is now for the
PC ExCom” and stating “it [PC Ex Com] ties everyone together.” These
changes have led to a marked increase in productivity and alignment
among groups previously working in silos. Reflecting on the procedural
changes, the PC acknowledges the challenges of adapting to new systems,
such as submitting detailed meeting notes and updating charge statements
regularly.
However, these practices offer long-term benefits by fostering a more
collaborative and productive environment that serves the broader struc-
tural engineering community. As the year concludes, the PC is primed to
continue its mission of empowering structural engineering professionals
and shaping the future of the profession.
#Structures25 : Scholarships are now OPEN!
The SEI Futures Fund, in collaboration with the ASCE Foundation, is offering scholarships to students and young professionals to
attend Structures Congress 2025, taking place from April 9-11 in Phoenix, Arizona. These scholarships cover registration and travel
costs, providing emerging engineers with the chance to gain insights from industry leaders, enhance technical knowledge through
hands-on workshops, and network with a diverse group of professionals. Additionally, student membership to ASCE/SEI is free, with
the first-year post-graduation also complimentary, emphasizing support for the next generation of structural engineers.
Application details available at structurescongress.org
Connecting NOAA and ASCE Standards
The PC Ties Everyone Together
In June, Managing Director of SEI, Jennifer Goupil, spoke at the ASCE-NOAA Taskforce
Workshop about the process of incorporating NOAA data into ASCE standards. The
workshop focused on using NOAA datasets to enhance ASCE 7 and other standards,
aiming to improve the accuracy and reliability of engineering practices through this
collaboration.
Learn more about the NOAA ASCE Taskforce: go.asce.org/asce-noaa-taskforce

71. 71AUGUST 2024
SEI Update News of the Structural Engineering Institute of ASCE
Call for Members: SEI Education and Leadership Committee
Want to shape and inspire the next generation of engineers?
SEI invites you to apply for a position on the SEI Education
and Leadership Committee. As a member, you will influence
the direction of structural engineering education by developing
state-of-the-art curricula and programs, leading initiatives that
promote leadership skills and professional growth within the SEI
community and collaborating with a diverse
group of professionals dedicated to advancing
the field.
Apply online with QR code! Select “SEI
Professional Community” from drop down and then
select “SEI Education and Leadership Committee.”
Call for Members: ASCE/SEI 41
Following the publication of ASCE/SEI 41-23 Seismic Evaluation and Retrofit of Existing Buildings, the committee
is reconstituting its roster to begin work on the 2029 edition. ASCE/SEI 41 is now accepting new members for the
next edition of the standard.
Applications for committees are being accepted until Sept 1, 2024.
Select SEI from the Institute drop-down, and then select the standard title.
Public Comment
Open
ASCE is conducting a reaffirmation
public comment period on the ASCE/
SEI 32-01 Design and Construction of
Frost-Protected Shallow Foundations.
The 45-day reaffirmation public com-
ment period will be held from June 21,
2024 – August 05, 2024. Visit go.asce.
org/standardsballoting
Accessing the Public Comment System
will require using or creating an ASCE
web user account. For additional questions
contact James Neckel, ASCE’s Codes and
Standards Manager, at [email protected]
Application details available at struc-
turescongress.org
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Full access to all ASCE standards referenced in the 2024, 2021, and 2018 editions of the International Building Code (IBC) is now available
with our new ASCE Referenced Standards: IBC Collection! This comprehensive package includes essential standards like ASCE 7, ASCE
24, ASCE 41, and more. Ensure your projects meet the highest industry standards. Visit https://amplify.asce.org/ibc.

72. American Society of Civil Engineers
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73. AUGUST 2024 73
Improv and the Engineer
Building skills in creativity can complement the logical side of the engineering profession for better problem
solving. By Mark Riley, Ph.D.
structural FORUM
T
he methods used by educators to train future engineers creates
analytical thinkers who can deconstruct complex challenges
into manageable tasks. Through lectures, readings, homework, and
experiments, engineering students develop their analytic think-
ing skills but often do not fully develop their communication
skills. In my 27 years as an educator, I and my colleagues have
incorporated more communication exercises into curricula but
despite these efforts, employers continue to seek improvements
in the student communication skills. Here I share an idea that I
believe has potential for meaningful improvement.
Recall the old saying that “if a tree falls in the forest and if no
one is there to hear it, does it make a sound?” If no one is around,
then there are no tympanic membranes which would convert the
pressure waves into what we know as sound. A related concept
applies to communication. If an individual talks at another and
the receiver does not understand what is being said, has com-
munication occurred? Good communication likely has not.
The 1970s tune, "The Logical Song," by the band Supertramp
exemplifies the challenge facing engineering educators. To quote,
“But then they sent me away to teach me how to be sensible
Logical, oh, responsible, practical
Then they showed me a world where I could be so dependable
Oh, clinical, oh, intellectual, cynical.”
We teach our students to be logical and, in the process, we restrict
the exercise of uninhibited creativity, which is needed to produce
well-rounded, engaged problem solvers who can communicate
with a variety of audiences. I suggest that the engineering com-
munity look to the tools of improvisation, or improv, to improve
communication skills.
Improv is founded on two rules: “yes” and “and.” The concept is
that an improviser accepts the situation that has been presented
to them (the “yes”) and adds information to the situation (the
“and”). These rules are simple to learn but challenging to put
into practice.
The skills of improv can be learned through a series of games
which on the surface seem quite silly; however, they serve to
practice active listening (the first part of good communication)
and removing mental filters that restrict us from speaking our
minds. One simple example is a game called “Introductions.”
Participants are paired up and introduce themselves by answering
questions: what their name is, where are they from, what kind
of music do they like, and what is one location they have not yet
visited but hope to travel to someday. These pairs match up with
another couple and introduce their partner to the new tandem.
Many improv games have a history that connect with the works of
Viola Spolin, often considered the mother of Improv. In Chicago
in the 1930s, Spolin created The Educational Playroom for chil-
dren in recognition that recent immigrants were not comfortable

74. STRUCTURE magazine 74
in speaking English.
Spolin developed a series of games which encouraged all the
children to participate and to gain confidence in speaking. The
games became popular and eventually her son, Paul Sills, brought
the games to adults as part of workshops intended for enjoy-
ment of the participants. The workshops gained an audience and
eventually begat the Second City comedy club and then Saturday
Night Live, SCTV, and others. Improv skills have been learned
by many communicators, comedians, and in recent years busi-
ness professionals.
Improv is not inherently about comedy or being funny. Sometimes
funny happens, but that’s not the point.
The tools of improv are helpful in improving the communication
skills especially of individuals who are reluctant to speak their
minds. This includes introverts, non-native English speakers, and
engineers who have been trained to not speak on any topic that
is outside of their area of expertise. For the past two years the
University of Nebraska-Lincoln has been teaching improv skills
to our graduate students.
Another game to build active listening skills is the “One sentence
story.” The participants arrange in a circle and start with a prompt
including the profession of a protagonist and a challenge they must
overcome. The group creates this individual hero’s journey by each
participant adding one sentence. They should agree and accept what
was said previously (yes) while adding new information (and) to move
the story along to resolution.
I am not suggesting abandonment of good practice in engineering,
but rather that we place some effort to exercise parts of our brains that
in many cases have not had the opportunity to flourish. Bodybuilders
who focus on growing their biceps, pecs, and shoulders exclusively
tend to look out of proportion with tiny, under-developed legs. Don’t
skip leg day!
The concept of “yes, and” can apply to many layers of communica-
tion. Contrast the effect of hearing “yes, and” relative to “no, but.”
For example, if an individual goes to a supervisor suggesting that they
add a popcorn machine to the breakroom as a perk for employees. The
supervisor’s natural instinct ought to be to support hearing creative
ideas from their staff even if they have misgivings. A response of “no,
but, we should encourage healthy eating” will not be well received
since after the word “no” the listener is likely to shut down. The word
“but” often invalidates all of the words that came before; that “no”
already has turned off the receiver. A better response is “yes, and, we
should encourage health eating." Same words at the end, but the start
of the sentence changes what is communicated.
Similarly, the “yes, and” approach is useful in the design process.
When developing new concepts, use this instead of brainstorming,
or association-based ideation. Start with one idea, accept that this
idea is worthy of discussion, then build out the concept as far as it
can go. Don’t critique the concept immediately. Start with another
seed idea and run it out to completion.
After the SEI Congress 2023, a survey of participants asked for
suggested programming at future meetings. Communication skills
and leadership skills were in the top 5. “Structural Engineering
Improvisation” made the list as a desired topic for leadership
development.
At NASCC24, we held a workshop on “Building a better structural
engineer through improvisation.” About 100 individuals participated
in a series of games to encourage active listening and to remove com-
munication filters. They seemed to have a good time especially in the
“One sentence story” that arose about a heroic chemical engineering
savant who realized the error of his/her ways and switched to structural
engineering. For this activity each participant had to accept what was
already established in the story and add one more sentence to advance
it. This was a good example of building upon what has come before,
of teamwork, of creativity, and of a willingness to speak without
concern for saying the wrong word in a non-judgmental space. These
are important lessons best learned through practice.
There is not yet a wealth of literature on engineers or scientists using
improv to advance their communication skills.
I encourage you to seek out activities that take you out of your
comfort zone and allow you to gain experience using the practices
of improvisation. Local community colleges often have improv or
theater classes which may be useful. That’s how I got my start down
this path and have enjoyed it tremendously.
Mark Riley, Ph.D., Chemical engineer, F. AAAS, F. AIMBE, F. IBE, as an Associate Dean
for Research at the University of Nebraska-Lincoln College of Engineering.
Additional resources are included in the online version of the
article at STRUCTUREmag.org.
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