Lecture on Temporary Structures by Dr. Welch

Temporary Structures during Construction

1. .
TEMPORARY STRUCTURES DURING
CONSTRUCTION
______________________________________________________________
 
Ronald Welch, Ph.D., P.E.
University of Texas at Tyler
John Brain, P.E.
Patent Construction Systems, A Harsco Company
 
 _____________________________________
 
ASCE Construction Institute Conference
Los Angeles, CA January 19, 2007
Contains material courtesy of Robert Ratay

2. .WHAT ARE TEMPORARY STRUCTURES ?
 
"Temporary structures are those structures that are erected
and used to aid in the construction of a permanent project . . .
providing access, support and protection."
 
They are "either dismantled and removed when the permanent
works become self-supporting or completed, or . . .Incorporated
into the finished work."
 
 
McGraw-Hill Encyclopedia of Science & Technology, 1997

3. Temporary Structures during Construction
Committee Charge
•Seek experts in areas not covered in current committee membership.
•Collect current resources, codes, standards, and best practices to
determine what is available. List the available codes and standards.
•Develop resources through committee expertise in areas not fully
populated with information.
•Begin dialogue with CI membership on issues concerning temporary
structures design and construction and the necessary qualifications for
engineers performing said work.
•Illicit input on current best practices and recommend improvements
•Prepare guidelines of best practices for design and construction of
temporary structures.
•Inform and educate engineer practitioners through seminars and
workshops.
•Promote research by developing a list of topic areas not fully developed
and understood.

4. Temporary Structures during Construction
Committee Charge
•Seek experts in areas not covered in current committee membership.
•Collect current resources, codes, standards, and best practices to
determine what is available. List the available codes and standards.
•Develop resources through committee expertise in areas not fully
populated with information.
•Begin dialogue with CI membership on issues concerning temporary
structures design and construction and the necessary qualifications for
engineers performing said work.
•Illicit input on current best practices and recommend improvements.
•Prepare guidelines of best practices for design and construction of
temporary structures.
•Inform and educate engineer practitioners through seminars and
workshops.
•Promote research by developing a list of topic areas not fully developed
and understood.

5. .
Loads Created by Construction Equipment
Construction Dewatering
Construction Ramps / Platforms / Vehicular Runway
Cofferdams
Earth Retaining Structures
Diaphragm / Slurry Walls
Underground / Tunneling Supports
Underpinning Foundations
Bridges
Scaffolding
Falsework / Shoring
Concrete Formwork
Bracing / Guying for Stability
Temporary structures in Repair / Restoration
Utilities – Underground / Overhead
Temporary buildings
Structures for the entertainment industry
Current Temporary Structures Sub-TopicsCurrent Temporary Structures Sub-Topics

6. Why?
MORE FAILURES OCCUR DURING CONSTRUCTION
THAN DURING THE LIFETIMES OF STRUCTURES
 
and
 
MOST CONSTRUCTION FAILURES INVOLVE
TEMPORARY STRUCTURES

7. .
EACH YEAR
•Close to 1,000 construction workers lose their lives
in the U.S.
 
•Direct and indirect cost of construction injuries is
more than $17 billion
 
•No one appears to have published the total of
property losses in construction failures

8. .
THERE APPEARS TO BE A MISMATCH OF THE
PRACTICES OF ONE GROUP ,
•the designers-of-record who by necessity distance
themselves from the construction of the project,
AND THE OBJECTIVES AND CAPABILITIES OF THE
OTHER GROUP,
•the constructors who by contract must perform
under the constraints of agreed time and money.

9. .
FAILURES OF
•unbraced excavations
•scaffolding
•falsework
•formwork
•excavation supports
•temporary erection shoring
•bracing and guying
(in approximately this order)
ARE THE MOST FREQUENT OCCURRENCES OF
CONSTRUCTION FAILURES

10. .
A TACIT ATTITUDE SEEMS TO PREVAIL IN THE
DESIGN-CONSTRUCTION INDUSTRY:
"these things" are temporary only, hence generally
less important, therefore greater risks are acceptable
than in permanent structures
But a dollar, or a life, lost at a construction site
is no less valuable or less tragic
than its loss elsewhere !

11. .
MANY ASPECTS OF TEMPORARY STRUCTURES
WORK ARE DIFFERENT FROM THOSE OF
PERMANENT STRUCTURES

12. .
•Intended function of the structure
•Nature of the loads
•Predictability of occurrence of the loads
•Certainty in the magnitudes of the loads
•Possibility of simultaneous occurrence of loads
•Strength and deformation characteristics of the material
•Reliability of the rated strength of the material (or member)
•Possible secondary stresses, redundancy and instability
•Condition of the member and its material (new, used, damaged, deformed)
•Acceptable behavior of the structure (such as tolerable deflections, vibrations)
•Acceptable probability of total failure
•Consequences of failure
•Construction tolerances
•Workmanship in the construction
•Inspection Standards
•Protection of the structure against damage, deterioration and extremities of weather
•Intended lifespan of the structure with the increasing probability of occurrence of
maximum loads, abnormal loads, damage and deterioration with time

13. .
BAD DESIGN PHILOSOPHIES AND PRACTICES
 
“These things” are temporary only, so go for
•Higher allowable stresses
•Lower safety factors
 

14. .
Loads Created by Construction Equipment
Construction Dewatering
Construction Ramps / Platforms / Vehicular Runway
Cofferdams
Earth Retaining Structures
Diaphragm / Slurry Walls
Underground / Tunneling Supports
Underpinning Foundations
Bridges
Scaffolding
Falsework / Shoring
Concrete Formwork
Bracing / Guying for Stability
Temporary structures in Repair / Restoration
Utilities – Underground / Overhead
Temporary buildings
Structures for the entertainment industry
Current Temporary Structures Sub-TopicsCurrent Temporary Structures Sub-Topics

15. Construction Institute - Temporary Structures Committee
Falsework and Shoring

16. What is Shoring?
Shoring (or Falsework), is a temporary structure
used to support vertical loads during the process of
construction. The loads supported can be from
freshly placed concrete, existing structures, or from
construction equipment.

17. Engineering RequirementsEngineering Requirements
for Shoring Designfor Shoring Design

18. Question?Question?
How does one go fromHow does one go from
To To
This This
This This
EngineeringEngineering

19. Requirements for Cast-In-Place ConcreteRequirements for Cast-In-Place Concrete
OSHA Construction Standard Subpart Q 1926.703OSHA Construction Standard Subpart Q 1926.703
(a)(a)General requirements for formworkGeneral requirements for formwork
(1) (1) Formwork shall be Formwork shall be designeddesigned, fabricated, erected, supported, , fabricated, erected, supported,
braced and maintained so that it will be capable of supportingbraced and maintained so that it will be capable of supporting
without failure all vertical and lateral loads that may be without failure all vertical and lateral loads that may be
reasonably be anticipated to be applied to the formwork. reasonably be anticipated to be applied to the formwork.
Formwork which is Formwork which is designed, fabricated, erected, supported, designed, fabricated, erected, supported,
braced and maintained in conformance with the Appendix to thisbraced and maintained in conformance with the Appendix to this
this section will be deemed to meet the requirements of thisthis section will be deemed to meet the requirements of this
paragraph.paragraph.
(2) (2) Drawings or plansDrawings or plans, including all revisions, for the jack layout,, including all revisions, for the jack layout,
formwork (including shoring equipment), working decks, andformwork (including shoring equipment), working decks, and
scaffolds, scaffolds, shall be available at the jobsiteshall be available at the jobsite

20. What A Engineer or Designer Requires To Provide What A Engineer or Designer Requires To Provide
Proper Technical SupportProper Technical Support
•Are you dedicating enough time for proper engineering design Are you dedicating enough time for proper engineering design
and review?and review?
•Do they have the most current contract documents (i.e. Do they have the most current contract documents (i.e.
Drawings, Specifications, Photographs)?Drawings, Specifications, Photographs)?
•Type of equipment to be usedType of equipment to be used
•Area to begin designArea to begin design
•Contractors preferences or ideasContractors preferences or ideas
•Any unusual site conditions or project requirementsAny unusual site conditions or project requirements
•Equipment availability (i.e. sizes NOT to use)Equipment availability (i.e. sizes NOT to use)
•Are drawings and calculations required for submittal?Are drawings and calculations required for submittal?
•Is a Professional Engineering Seal Required?Is a Professional Engineering Seal Required?
•Once drawings are completed, a timely review by field Once drawings are completed, a timely review by field
personnel and project management with positive or negative personnel and project management with positive or negative
feedback returned to Engineering in a realistic and timely feedback returned to Engineering in a realistic and timely
manner so revisions can be done.manner so revisions can be done.

21. Engineering’s RoleEngineering’s Role
Engineering plays a Engineering plays a critical rolecritical role in the overall in the overall
success on most projects where shoring is being success on most projects where shoring is being
used. Shoring Engineers and Designers can provide used. Shoring Engineers and Designers can provide
contractors with the contractors with the knowledge and experienceknowledge and experience that that
allows them to be competitive and have a allows them to be competitive and have a safe safe
working environmentworking environment. Shoring Engineers and . Shoring Engineers and
Designers are Designers are highly specialized in the skillshighly specialized in the skills required required
to form and shore complex shapes formed from cast-to form and shore complex shapes formed from cast-
in-place concrete, supporting high concentrated in-place concrete, supporting high concentrated
loads and keeping your workforce safe. These design loads and keeping your workforce safe. These design
professionals can also provide you with many professionals can also provide you with many
alternative waysalternative ways to solve these complex situations, to solve these complex situations,
which are now common on today’s projects.which are now common on today’s projects.

22. How Engineering Supports You!!How Engineering Supports You!!
•Layout and field assembly drawingsLayout and field assembly drawings
•CalculationsCalculations
•Product usage, capacities and capabilitiesProduct usage, capacities and capabilities
•Proper product applicationsProper product applications
•Design of standard and special product Design of standard and special product
componentscomponents
•Field inspections and job walksField inspections and job walks
•SafetySafety

23. Standards Used In The Design And Erection Of Standards Used In The Design And Erection Of
Shoring SystemsShoring Systems
•American Concrete Institute – Committee 347American Concrete Institute – Committee 347
•Scaffolding, Shoring & Forming InstituteScaffolding, Shoring & Forming Institute
•Occupational Safety and Health AdministrationOccupational Safety and Health Administration
•Local and State Building CodesLocal and State Building Codes
•AASHTOAASHTO
•Local State Department of TransportationLocal State Department of Transportation
•Military SpecificationsMilitary Specifications
•Department of Energy SpecificationsDepartment of Energy Specifications

24. Standards Used In The Design And Erection Of Standards Used In The Design And Erection Of
Shoring SystemsShoring Systems
In House Engineering Department In House Engineering Department
Specifications and Design GuidesSpecifications and Design Guides

25. Without the proper communication, even the Without the proper communication, even the
smallest project can potentially turn into:smallest project can potentially turn into:
““I wish I never Quoted This Project”I wish I never Quoted This Project”

26. Various Shoring SystemsVarious Shoring Systems
Post ShoresPost Shores
Frame ShoringFrame Shoring
Table SystemsTable Systems
Truss &Truss &
Column MountedColumn Mounted
Post/Ledger SystemPost/Ledger System
Drop Head/Post Drop Head/Post
Systems Systems
Adjustable BeamAdjustable Beam
SystemsSystems

27. PostPost ShoresShores
•One of the most common shoring One of the most common shoring
systems/methods of shoringsystems/methods of shoring
•Simplest to use, little training requiredSimplest to use, little training required
•LightweightLightweight
•Post have various ranges in shoring Post have various ranges in shoring
heightheight
•Load capacity will vary with heightLoad capacity will vary with height
•Can be used in tight and unusual Can be used in tight and unusual
shapesshapes

28. Single Post Shore Safety RuleSingle Post Shore Safety Rule
As Recommended by the Scaffolding, Shoring As Recommended by the Scaffolding, Shoring
and Forming Institute, Inc.and Forming Institute, Inc.
Item CItem C. Plumb All Post Shores As The Erection Plumb All Post Shores As The Erection
ProceedsProceeds. Check plumb of post shores . Check plumb of post shores JUST PRIOR JUST PRIOR
TO POURTO POUR
Item G.Item G. For Stability, Single Post Shores Shall Have For Stability, Single Post Shores Shall Have
Adequate BracingAdequate Bracing provided in the longitudinal, provided in the longitudinal,
transverse and diagonal directions. Bracing shall be transverse and diagonal directions. Bracing shall be
installed as the shores are being erected.installed as the shores are being erected.

29. Single Post Shore Safety RuleSingle Post Shore Safety Rule
Per OSHA Construction StandardPer OSHA Construction Standard
Subpart Q 1926.703Subpart Q 1926.703 Whenever single post shores are Whenever single post shores are
used one on top of the other (tiered), the employer used one on top of the other (tiered), the employer
shall comply with the following specific requirements shall comply with the following specific requirements
in addition to the general requirements for formwork:in addition to the general requirements for formwork:
(i) The design of the shoring shall be prepared by a (i) The design of the shoring shall be prepared by a
qualified designer and the erected shoring shall be qualified designer and the erected shoring shall be
inspected by an engineer qualified in structural inspected by an engineer qualified in structural
design.design.

30. Post Shores Not PlumbPost Shores Not Plumb
No Adequate BracingNo Adequate Bracing

31. Proper Usage of Single Post ShoresProper Usage of Single Post Shores

32. Shoring FramesShoring Frames
•One of the most common shoring systems/methods One of the most common shoring systems/methods
of shoring. of shoring.
•Simple to use, little training required. Simple to use, little training required.
•Most field personnel are knowledgeable in Most field personnel are knowledgeable in
assembly and safe usage of systems assembly and safe usage of systems
•Load capacities range from 10,000 lbs per leg to Load capacities range from 10,000 lbs per leg to
50,000 lbs per leg50,000 lbs per leg
•Systems are variable in frame heights and brace Systems are variable in frame heights and brace
sizes sizes
•Multitude of accessories to meet your requirementsMultitude of accessories to meet your requirements
•Have an integral screw leg to allow fine adjustmentHave an integral screw leg to allow fine adjustment
•Most Shoring suppliers have a substantial Most Shoring suppliers have a substantial
inventory on handinventory on hand

33. Shoring FramesShoring Frames

34. Steel Frame Shoring Safety RuleSteel Frame Shoring Safety Rule
As Recommended by the Scaffolding, Shoring As Recommended by the Scaffolding, Shoring
and Forming Institute, Inc.and Forming Institute, Inc.
Item O.Item O. Avoid Eccentric Loads On U-Heads, Top Plates Avoid Eccentric Loads On U-Heads, Top Plates
and Similar Members By Centering Stringers On Those and Similar Members By Centering Stringers On Those
Members.Members.

36. ““Simple Tower Layout” – Drafting StandardSimple Tower Layout” – Drafting Standard
This is the reason why stringers are
most often incorrectly erected

37. Notice how “stringer” runs Notice how “stringer” runs
diagonally from one leg to the diagonally from one leg to the
otherother
““Stringer” is CENTERED on middle legStringer” is CENTERED on middle leg

38. Post/Ledger SystemsPost/Ledger Systems
•One of the newer shoring systems to be introduced to the US One of the newer shoring systems to be introduced to the US
construction marketconstruction market
•Most of these systems have been developed by European Most of these systems have been developed by European
Shoring suppliers (Metric)Shoring suppliers (Metric)
•These systems require a more “technical” erection crewThese systems require a more “technical” erection crew
•These systems are lightweight, most of the components are made These systems are lightweight, most of the components are made
from aluminum.from aluminum.
•High leg capacities. In certain configurations a single leg can High leg capacities. In certain configurations a single leg can
carry 24,000 lbscarry 24,000 lbs
•Can be broken down into single posts for re-shore operationsCan be broken down into single posts for re-shore operations
•Systems can be assembled into tables or tall towers and flown Systems can be assembled into tables or tall towers and flown
into the required location on a projectinto the required location on a project
•Fast erection/assembly timesFast erection/assembly times
•Uses less parts than standard frame systemsUses less parts than standard frame systems
•System is best used for heavy slabs such as Turbine Pedestal System is best used for heavy slabs such as Turbine Pedestal
Tops, Linear Accelerator or any other type of heavy reinforced Tops, Linear Accelerator or any other type of heavy reinforced
concrete structuresconcrete structures

39. Post/Ledger SystemsPost/Ledger Systems

40. Adjustable Beam SystemAdjustable Beam System
•One of the older systems on the marketOne of the older systems on the market
•Simple to useSimple to use
•Units come in various span combinations. Units come in various span combinations.
Span sizes vary from 4’ up to 30’Span sizes vary from 4’ up to 30’
•Great for tight locations or areas where Great for tight locations or areas where
obstructions limited the use of standard obstructions limited the use of standard
shoring towers.shoring towers.
•Can be used in tight and unusual shapesCan be used in tight and unusual shapes
•Available in both steel and aluminumAvailable in both steel and aluminum

41. Adjustable Beam SystemsAdjustable Beam Systems

42. Table SystemsTable Systems
•These systems are best used on high rise type structures where These systems are best used on high rise type structures where
there is a substantial amount of reuse there is a substantial amount of reuse
•Table units are designed for your projects requirements Table units are designed for your projects requirements
•These systems components are either constructed from aluminum These systems components are either constructed from aluminum
or steelor steel
•These systems use modular parts that simply bolt togetherThese systems use modular parts that simply bolt together
•Little re-shoring of slabs is required due to limiting leg locationsLittle re-shoring of slabs is required due to limiting leg locations
•As for Column Mounted Tables, no re-shoring will be required, due As for Column Mounted Tables, no re-shoring will be required, due
to tables being supported by jacks at the structures column or to tables being supported by jacks at the structures column or
shearwallsshearwalls
•These systems all require the use of tower or track type cranes to These systems all require the use of tower or track type cranes to
movemove
•Contractors must keep crane location and capacities in mind when Contractors must keep crane location and capacities in mind when
deciding on using one these types of systemsdeciding on using one these types of systems
•Assembly area is typically required since these systems are job Assembly area is typically required since these systems are job
built. In some cases shoring suppliers may assemble tables for built. In some cases shoring suppliers may assemble tables for
the contractorthe contractor

43. Table SystemsTable Systems

45. How many systems are being used on this project?How many systems are being used on this project?

46. Column Hung SystemColumn Hung System
Post/Ledger SystemPost/Ledger System
Truss SystemTruss System

47. ““Bad Practice”Bad Practice”
Care must be taken during ALL stages
of assembly on any type of Shoring
Systems. If care is NOT taken, there
is a potential for failure of that system.

48. Since this jack is not plumb, damage or failure of the Since this jack is not plumb, damage or failure of the
jack may occurjack may occur
This jack has been installed properlyThis jack has been installed properly

49. Drophead/Post SystemsDrophead/Post Systems
•This is the newest system to be introduced to the US This is the newest system to be introduced to the US
construction marketconstruction market
•System uses a simple post shore that supports a ledger which System uses a simple post shore that supports a ledger which
can in turn support a prefabricated panel or LVL wood joistcan in turn support a prefabricated panel or LVL wood joist
•The benefit to this system is that the post stays in place while The benefit to this system is that the post stays in place while
the decking material is stripped out around itthe decking material is stripped out around it
•These systems use a drop head which “drops down” to allow These systems use a drop head which “drops down” to allow
the joist/panel and ledgers to be removed and cycled onto the the joist/panel and ledgers to be removed and cycled onto the
next pour, leaving the post in place for re-shoringnext pour, leaving the post in place for re-shoring
•Post are available in various heightsPost are available in various heights
•Panels and LVL joist are available in several standard sizesPanels and LVL joist are available in several standard sizes
•For a typical 12” thick concrete slab, the typical area on a post For a typical 12” thick concrete slab, the typical area on a post
will be 48 sq. ft. (Depending on shoring height)will be 48 sq. ft. (Depending on shoring height)

51. National Shoring SuppliersNational Shoring Suppliers
•Patent Construction SystemsPatent Construction Systems
•Doka, USADoka, USA
•PeriPeri
•EFCOEFCO
•Aluma SystemsAluma Systems
•Waco ScaffoldingWaco Scaffolding
•Symons CorporationSymons Corporation
•TitianTitian
•Hi-Lite, LTD.Hi-Lite, LTD.
•MevaMeva

52. References and Design PublicationsReferences and Design Publications
•Formwork For ConstructionFormwork For Construction by Mary K. Hurd SP-4, ACI by Mary K. Hurd SP-4, ACI
347. 6th Edition, The American Concrete institute, P.O. 347. 6th Edition, The American Concrete institute, P.O.
Box 9094, Farmington Hills, Michigan, 48333-9094. The Box 9094, Farmington Hills, Michigan, 48333-9094. The
“Bible” for any formwork or shoring Engineer or “Bible” for any formwork or shoring Engineer or
designerdesigner
•Handbook of Temporary Structures in ConstructionHandbook of Temporary Structures in Construction by by
Robert T. Ratay, 2nd Edition, 1996, The McGraw-Hill Robert T. Ratay, 2nd Edition, 1996, The McGraw-Hill
Companies, ISBN 0-07-051261-2 . This is a good book Companies, ISBN 0-07-051261-2 . This is a good book
that a designer/contractor on the proper design and that a designer/contractor on the proper design and
usage of temporary structures in construction. Covers usage of temporary structures in construction. Covers
items such as underpinning, earth retention, shoring, items such as underpinning, earth retention, shoring,
scaffolds, formwork, piles, and many other topics.scaffolds, formwork, piles, and many other topics.
•AASHTO Guide Design Specification for Bridge AASHTO Guide Design Specification for Bridge
Temporary WorksTemporary Works
•AASHTO Construction Handbook for Bridge Temporary AASHTO Construction Handbook for Bridge Temporary
WorksWorks
•ASCE 37-02 Design Loads on Structures During ASCE 37-02 Design Loads on Structures During
ConstructionConstruction
•Masonry Wall Bracing StandardsMasonry Wall Bracing Standards

53. Columbia Building – Washington D.C.Columbia Building – Washington D.C.

55. Post Shores Shown Post Shores Shown
CorrectlyCorrectly
Loads on structure Loads on structure
are indicated on for are indicated on for
Engineer of Record Engineer of Record
to reviewto review

58. Dulles ATCTDulles ATCT

59. All erection information All erection information
(spacing's, type or (spacing's, type or
equipment, etc.) givenequipment, etc.) given
Erection SequenceErection Sequence
Specific Notes Specific Notes
Indicated on DrawingIndicated on Drawing

60. All Required Details All Required Details
GivenGiven

61. Sections & Details Sections & Details
for ALL Conditionsfor ALL Conditions
Areas indicated that are Areas indicated that are
other responsibilities for other responsibilities for
designdesign

64. Tampa Airport MonorailTampa Airport Monorail

67. Connection DetailConnection Detail

68. Built per detail shown on drawingsBuilt per detail shown on drawings

69. .
TEMPORARY STRUCTURE DESIGNER'S DONT'S
 
•Don't design for a contractor you don't know
•Don't design unless you understand the construction process
in which the temporary structure will be used
 
•Don't reduce design loads
•Don't increase allowables
•Don't reduce safety factors
. . . . . unless you have adequately considered all factors, and
. . . . . unless inspection is part of your services
•Don't allow used materials without continuous quality control
•Don't allow material substitutions without your approval

70. .
ROLES AND RESPONSIBILITIES OF PROJECT
DESIGN ENGINEER
(STRUCTURAL ENGINEER OF RECORD)
 
•Evaluate effects of temporary structures on the
permanent structure
 
•Normally not involved in the design of temporary
structures – means-and-methods
 
•Usually does not review temporary structures shop
drawings

71. .
THE BEST WAYS TO MITIGATE CONSTRUCTION
FAILURES ARE, OBVIOUSLY:
•competent designs
•good construction practices
•utmost care
•strict inspection
•unwavering enforcement of high standards
•clear definition of responsibilities

72. .
Loads Created by Construction Equipment
Construction Dewatering
Construction Ramps / Platforms / Vehicular Runway
Cofferdams
Earth Retaining Structures
Diaphragm / Slurry Walls
Underground / Tunneling Supports
Underpinning Foundations
Bridges
Scaffolding
Falsework / Shoring
Concrete Formwork
Bracing / Guying for Stability
Temporary structures in Repair / Restoration
Utilities – Underground / Overhead
Temporary buildings
Structures for the entertainment industry
Current Temporary Structures Sub-TopicsCurrent Temporary Structures Sub-Topics

73. Questions?
•POCs:
•Ron Welch, Committee Chair
[email protected], 903-566-7002
•John Brain, Committee Secretary,
[email protected], [phone]