Lecture WAAM_LEZ1_summerschool2024_MP.pdf

Lecture Summer School Bologna 2024

1. Characterizati
on of Metal 3D
printed
elements
Prof. Michele Palermo,
University of Bologna
SUMMER SCHOOL
“METAL 3D PRINTING IN
CONSTRUCTION”
July 8-10, 2024
University of Bologna, Italy

2. TheresearchgroupactivelycollaborateswiththefollowingotherUNIBO
divisionsanddepartments:
-Surveyandgeomatics(DICAM)
-Metallurgyandtechnology(DIN)
-Roboticsandautomatedcontrols(DEI)
-Architecture(DA)
InternationalcollaborationswithSMEs,technologyprovidersandRTOs:
WHO WE ARE?
AdditiveManufacturingandAutomationinConstruction(AMAC)research
groupiscomposedbyprofessors,researchersandpost-docfromDICAM
departmentatUniversityofBologna(Italy),StructuralEngineeringdivision.
Since2017weworkataninterdisciplinarylevelonthedevelopmentofmetal
AMtechnology(Wire-and-ArcAdditiveManufacturing)forlargepartswith
potentialapplicationsintheconstruction,infrastructureandenergysectors.

3. •Technological evolution in the construction industry
•Wire arc additive manufacturing
•Characterization of WAAM continuous elements
Geometrical
Microstructure
Mechanical
•Characterization of dot-by-dot WAAM elements
Geometrical
Microstructure
Mechanical
•Structural design for WAAM
Lecture layout

4. source: www.wikiwand.com/en/Concrete
Technological evolutionin theconstructionindustry
Photos: H. Kloft
System Formwork and Reinforcement Integration, 2021System Formwork and Reinforcement Integration, 1912

5. Low productivtiy, inefficientmaterial usage, high CO
2emissions and…
Development of productivity in different production areas
Grafik: ITE / TU BS
auf Basis der Daten des
Statistischen Bundesamtes
von 2017 Photo: H. Kloft
Craftedconstructionsites

6. The construction industry needs its own
digital manufacturing technologies for
individualized industrial fabrication…

7. Additive Manufacturing

8. Additive Manufacturing

9. Additive Manufacturing towards Industry 4.0

10. Additive Manufacturing for Circular Economy
Sauerwein, M., Doubrovski, E., Balkenende, R., & Bakker, C. (2019). Exploring the potential of additive
manufacturing for product design in a circular economy.Journal of Cleaner Production,226, 1138-1149.4

11. Benefits for AM in construction
•Environmentally friendly
•No waste
•Potentially use recycled base material
•Able to create complex design
•Ideally complete freedom in the design for the architect/designer
•Safety for construction workers
•Reduced risks on site
•Reduced amount of people required on site

12. Challenges for AM in construction
•Design for AM
•Build setup
•Process simulation
•Material properties
•Data capture and management
•Part qualification
DESIGN
FOR AM
(DfAM)
BUILD
SETUP
PROCESS
SIMULATION
MATERIAL
ANALYSIS
DATA CAPTURE
AND
MANAGEMENT
PART
QUALIFICAT
ION

13. Metal Additive Manufacturing

14. Metal Additive Manufacturing

15. Metal Additive Manufacturing
•Binder Jetting
•Powder Bed Fusion (PBF)
•Sheet Lamination
•Directed Energy Deposition (DED)

16. 2015: ARUP -
Amsterdam
2010: Nematox
2019: Airmesh-
Singapore
2018: MX3D Bridge -
Amsterdam
2010 2015 2017 2018 2019 2020
2017: Glass Swing –TU
Delft
2020: Takenaka
connector-Japan
Metal AM in construction

17. Metal AM in construction
NEMATOX FAÇADE NODE (2010)
University of Applied Sciences in Detmold, Germany
Aluminum node
Powder Bed Fusion

18. Metal AM in construction
ARUP NODE(2014)
ARUP
Stainless steel node
Powder Bed Fusion

19. Metal AM in construction
MX3D BRIDGE(2018)
MX3D, Netherlands
Stainless steel bridge
Wire-and-Arc Additive Manufacturing

20. Metal AM in construction
DIAGRID COLUMN(2018)
MX3D, Netherlands
University of Bologna, Italy
Stainless steel column
Wire-and-Arc Additive Manufacturing

21. WAAM:Weld-basedmetal 3D-printing consisting of an off-the-shelf welding equipment mounted
on top of a robotic arm.
CONTINUOUS PRINTING DOT-BY-DOT PRINTING
Wire-and-Arc Additive Manufacturing: printing strategies

22. ADVANTAGES:
Fast production
No geometrical constraint in shape
and dimension
High resistance of the printed material
OPEN ISSUES:
Lack of material characterization
Lack of mechanical and geometrical
characterization of the printed elements
Lack of current standard design
procedures
Wire-and-Arc Additive Manufacturing

23. Highpotentialinrealizinginnovativestructural
elementswithimprovedperformancesthrough
optimizationandreducedmaterialuse->
environmentalimpact
Multidisciplinaryintegratedcompetencesin
fabrication,conceptualstructuraldesign,testingand
verification.
CONCEPTUAL STRUCTURAL
DESIGN
DESIGN PROJECT
FABRICATION
TESTING &
VERIFICATION
WAAM for sustainable construction
Wire-and-Arc Additive Manufacturing

24. Approaches for structural design
ADVANCED NUMERICAL
MODELLING
(“digital twin”)
CONVENTIONAL DESIGN
TAILORED TO WAAM
(partial safety factors)
CONVENTIONAL DESIGN
APPROACH
(partial safety factors)
Semi-probabilistic approach to
calibrate the design values and
partial safety factors for the
main material properties
Constant geometry
(deterministic value of the
resistant cross-section)
Linear elastic material behavior
Detailed non-linearmaterial
behavior
Accurate geometrical
irregularities (from scan 3D)
Semi-probabilistic approach to
calibrate the design values and
partial safety factorsfor the
main material properties
accounting for the anisotropic
behavior
Effective material properties
and geometry

25. ADVANCED NUMERICAL
MODELLING
(“digital twin”)
CONVENTIONAL DESIGN
TAILORED TO WAAM
(partial safety factors)
CONVENTIONAL DESIGN
APPROACH
(partial safety factors)
Semi-probabilistic approach to
calibrate the design values and
partial safety factors for the
main material properties
Constant geometry
(deterministic value of the
resistant cross-section)
Linear elastic material behavior
Detailed non-linearmaterial
behavior
Accurate geometrical
irregularities (from scan 3D)
Semi-probabilistic approach to
calibrate the design values and
partial safety factorsfor the
main material properties
accounting for the anisotropic
behavior
Effective material properties
and geometry
WHAT WE NEED:
Evaluation of the effective
parameters
Calibrationof partial safety
factors
Estimation of the
constitutive/mechanical
behaviorof WAAM materials/
structural elements
Structural Design approaches

26. WAAM
PROCESS
Experimental
characterization
Structural design
guidelines
Computational
structural design
Experimental
characterization
Structural design
guidelines
Orthotropic
material model
Computational
structural design
Our research at UNIBO
CONTINUOUS
PRINTING
DOT
-
BY
-
DOT
PRINTING

27. WAAM –
CONTINUOUS
PRINTING
EXPERIMENTAL
CHARACTERIZATION
STRUCTURAL DESIGN
GUIDELINES
DEFINITION OF THE ORTHOTROPIC
MATERIAL MODEL
COMPUTATIONAL
STRUCTURAL DESIGN

28. Issues to be
addressed
Influence of the WAAMprocess parameters
on the geometrical, mechanical and
microstructural properties
Update of the current structural building
codesfor WAAM-produced structures
Definition of ad-hoc experimentally
calibrated orthotropic material modelfor
WAAM steels
Exploration of new optimized designs for
WAAM structural elements

29. STRUCTURAL DESIGN FOR ADDITIVE MANUFACTURING (SDAM)
The“blended”structuraldesignapproach:
•ExplorethepotentialofWAAMtechnologyfor
new«optimized»structuralsolutionsat
differentscalesintegrating(1)basicprinciples
ofstructuraldesign(efficientstructural
solutions)with(2)computationaldesign&
topologyoptimization,(3)printingprocess
featuresintermsofcapabilities,limitations,(4)
mechanicalandgeometricalproperties
Applicationsatdifferentscales:
•Wholestructuralsystem
•Singlestructuralelement/component
“Blended design approach”
(Laghi et al. 2022)

30. Constitutive behavior of steel material
Key mechanical properties for structural steel:
Young’s modulus,
Proportional stress
0.2% proof stress,
Ultimate Tensile Strength
Elongation at rupture
Poisson’s ratio
strain
stress
E
ε
0.2
0.2%
σ
0.2
ε
r
σ
u
0.2% proof stress
Ultimate tensile
strength
Elongation at
rupture
Young’s
modulus
σ
p
Proportional stress
F F

31. Stress strainbehaviourfor machinedand as-builtspecimens
Effectivestress basedon effectivearea for as-builtspecimens

32. Experimental characterization
Geometrical characterization: surface
roughness and cross sectional areas
Microstructural/ metallographic analysis with
EBSD and XRD
Mechanical tensile test on machined / as
built specimensalong three main directions
with respect to the printing layers: T, L, D.
LVDTand optical-basedmonitoringsystem
(DIC) to acquire full field of strain (both
longitudinal and transversal).
Tested materials @ UNIBO: stainless steel 304L
(machined + as built), carbon steel (machined)
Carbon steelER 70S-6
Stainlesssteel308LSi

33. The dog-bone testedspecimensby UNIBO

34. z
y
x
t(x
i,y
i)
6
9
m
m
20 m
m Geometrical characterization
3D model from scanningacquisition
on one as-built specimen (on 40
millions points)
Detailed study of the distribution of
surface roughness along the two
surfaces of the specimen (upper and
lower)
Detailed study of the distribution of
thicknessalong the two directions
(along the specimen and across it)
modelled as a random process.
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.
Stainlesssteel308LSi

35. Geometrical characterization
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.
Estimation of surface roughness from the two
point-clouds of upper and lower surfaces.
From the Z coordinates at zero-mean for each
surface, estimation of peaksand pits.
Values of arithmetical mean height and root
mean square height of 0.15-0.3 mm.
Maximumpeaks and pits (large dots) of around
0.8 mm.y
z
A
A
Section A-A
z
x
y
Stainlesssteel308LSi

36. Geometrical characterization
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.
Characterization of the thickness distribution for structural design purposes
Selected values of thickness t(x
i,y
i) were extracted along the two directions xand
y(total of 322 points)
For a fixed value of y
i, the set of measurements along the lengtht(x|y
i)can be
interpreted as the single realization of a random processt(x).
Values taken at a fixed value of x
iare taken across the ensemble t(x
i|y).
Stainlesssteel308LSi

37. Geometrical characterization
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.
The mean orthogonally to printing direction(across-
the-ensemble) has small variability, meaning that the
process can be considered stationaryin average
sense.
The mean along the printing direction (along-the-
length) has larger variability, meaning that the
process cannotbe considered ergodicin an average
sense.
Overall, the statistical distribution of thickness values
has a mean of 3.48 mm (with respect to a nominal
value of 4 mm) and a standard deviation of 0.2 mm.
Stainlesssteel308LSi

38. Geometrical characterization: : the effective area
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.
Overall, the mean effective area
corresponds to a thicknessof 3.58 mm
for T specimens and 3.76 mm for L
specimens. eff
eff
F
A

Estimation of the effective cross-sectional area of as-
built specimens from volume equivalency (from
measures taken with an hydraulic scale and according
to the Archimedes’ principle)
The effective areais considered constantover the
gauge length of the specimen to estimate the related
stresses (from experimental tests)

39. Material characterization: microstructure
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Ceschini, L., Trombetti, T., “Tensile properties and microstructural features of 304L
austeneticstainless steel produced by Wire-and-Arc Additive Manufacturing”, Journal of Advanced Manufacturing Technology, 2020.
L T D
Stainlesssteel308LSi
Marked Oriented columnar
grain growth leading to
macroscopic mechanical
anisotropy

40. Material characterization: key parameters
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Ceschini, L., Trombetti, T., “Tensile properties and microstructural features of 304L
austeneticstainless steel produced by Wire-and-Arc Additive Manufacturing”, Journal of Advanced Manufacturing Technology, 2020.
Stainlesssteel308LSi

41. Material characterization: key parameters
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Ceschini, L., Trombetti, T., “Tensile properties and microstructural features of 304L
austeneticstainless steel produced by Wire-and-Arc Additive Manufacturing”, Journal of Advanced Manufacturing Technology, 2020.
106
353
553
135
341
567
243
413
605
0
100
200
300
400
500
600
700
WAAM - T
WAAM - L
WAAM - D
Young’s modulus
[GPa]
0.2% proof
stress [MPa]
Ultimate tensile
strength [MPa]
EC3
EC3
EC3
High anisotropy in terms of Young’s modulus
(D highest, T lowest)
-60% to +25% Young’s modulus with respect
to traditionally manufactured stainless steel
+75% yield stress with respect to
traditionally manufactured stainless steel
Almost constantresults for ultimate tensile
strengthvalues (and in line with standard
EC3 values)
Stainlesssteel308LSi

42. Material characterization:key parameters
Estimation of Poisson’s ratio along T and L directions (from DIC
measures).
+15% to +50% with respect to the standard value for stainless steel.
Symmetricalrelationship between E and ν(typical of orthotropic
materials)
0,35 0,35 0,36
0,370,38
0,49
0,46
0,43
0,00
0,10
0,20
0,30
0,40
0,50
0,60
T-LL-T
Poisson’s ratio
Plate 1 Plate 2Plate 3Plate 4
EC3
Laghi, V., Tonelli, L., Palermo, M., Bruggi, M., Sola, R., Ceschini, L., Trombetti, T., “Orthotropic elastic model
of Wire-and-Arc Additively Manufactured stainless steel”, Additive Manufacturing, 2021.L TL T LT
EE
Stainlesssteel308LSi

43. Mechanical characterization: stress-strain curves
Stainlesssteel308LSi

44. Mechanical properties: machined vs as-built
Laghi, V., Palermo, M., Gasparini, G., Girelli, V.A., Trombetti, T., “On the influence of the geometrical irregularities in the
mechanical response of Wire-and-Arc Additively Manufactured planar elements”, Journal of Constructional Steel Research, 2021.L -longitudinal
T

-
t
r
a
n
s
v
e
r
s
a
l
Comparing the mechanical properties taken from experiments on machined and as-built
specimens, there is slight difference between the two sets of values.
The results confirm that the influence of the geometrical irregularities in the main mechanical
properties are of the order of the variability of the test results.
The estimation of the effective cross-section from volume equivalency provides sufficiently good
approximation on the main mechanical properties for as-built WAAM elements.
Direction LDirection T
Stainlesssteel308LSi

45. Orthotropic elastic model: formulation
Orthotropic model for WAAM material:
•From the experimentaltests: E
x-E
y-v
xy-v
yx
•Symmetrical relationship: x yx y xy
EE   1/ / 0
/ 1/ 0
0 0 1/
x x yx y x
y xy x y y
xy xy xy
EE
EE
G
  
  

      
     
   
   
      T
L
x
y
Laghi, V., Tonelli, L., Palermo, M., Bruggi, M., Sola, R., Ceschini, L., Trombetti, T., “Orthotropic elastic model of
Wire-and-Arc Additively Manufactured stainless steel”, Additive Manufacturing, 2021.
Stainlesssteel308LSi

46. Orthotropic elastic model
Calibrationof the WAAM orthotropic model from experiments on the four plates
tested.
Maximum Young’s modulus of more than 250 GPa for orientations of around 42°
(with respect to the printing layer)
Maximum shear modulus of more than 150 GPa at 0°and 90°.
YOUNG’S
MODULUS
SHEAR
MODULUS
Laghi, V., Tonelli, L., Palermo, M., Bruggi, M., Sola, R., Ceschini, L., Trombetti, T., “Orthotropic elastic model of
Wire-and-Arc Additively Manufactured stainless steel”, Additive Manufacturing, 2021.
Stainlesssteel308LSi

47. Orthotropic elastic model
Laghi, V., Tonelli, L., Palermo, M., Bruggi, M., Sola, R., Ceschini, L., Trombetti, T., “Orthotropic elastic model of
Wire-and-Arc Additively Manufactured stainless steel”, Additive Manufacturing, 2021.

48. Material characterization along the thickness
Carbon steelER 70S-6

49. Material characterization along the thickness
Carbon steelER 70S-6
Laghi, Vittoria, et al. "Mechanical and microstructural features of wire-and-arc additively manufactured carbon
steel thick plates."The International Journal of Advanced Manufacturing Technology127.3 (2023): 1391-1405.

50. Material characterization
Carbon steelER 70S-6
Values of the key
mechanical parameters are
adequate for structural
applications.
Strength values in line with
S275 structural steel.
Levels of ductility are quite
higher than the minimum
recommended values for
structural steel.

51. Material characterization
Carbon steelER 70S-6
Laghi, Vittoria, et al. "Mechanical and microstructural features of wire-and-arc additively manufactured carbon
steel thick plates."The International Journal of Advanced Manufacturing Technology127.3 (2023): 1391-1405.

52. Material characterization: microstructure
sound microstructure with
minor traces of typical
solidification defects
essentially homogeneous
microstructure along the
three main planes leading
to isotropic mechanical
behavior
Laghi, Vittoria, et al. "Mechanical and microstructural features of wire-and-arc additively manufactured carbon
steel thick plates."The International Journal of Advanced Manufacturing Technology127.3 (2023): 1391-1405.
Carbon steelER 70S-6x

53. Structural design guidelines
EUROPEAN
STANDARD CODE
DESIGN ASSISTED
BY TESTING
NEW CODE PROVISIONS
FOR WAAM
•Characteristic and
design values for
strength
•Pre-definedsafety
factors
•Estimationof the
design values and
safety factors from
experiments
•Characteristic and design
values for strength based
on the printing
orientation
•Updated safety factors
accounting for the
geometrical and
mechanical variability

54. EUROPEAN
STANDARD CODE
DESIGN ASSISTED
BY TESTING
NEW CODE PROVISIONS
FOR WAAM
•Characteristic and
design values for
strength
•Pre-definedsafety
factors
•Estimationof the
design values and
safety factors from
experiments
Structural design guidelines
•Characteristic and design
values for strength based
on the printing
orientation
•Updated safety factors
accounting for the
geometrical and
mechanical variability

55. The calibrated material properties are:
•Yielding stress (corresponding to 0.2% proof stress): f
yk-f
yd-??????
??????1
•Ultimate tensile stress: f
tk-f
td-??????
??????2
•Young’s modulus: E
Structural design guidelines
Calibrationof the key material properties from
experimentson machined specimens for the three
directions (T, L, D)
Two approaches:
•From Annex D of Eurocode 0 (based on
experimental mean and st.dev)
•From best-fit Log-Normal distributions (based
on fractiles) accounting for a proper CI
Equivalent to ??????
??????0
(=1.10 according to
EN1993:1-4)
Equivalent to ??????
??????2
(=1.25 according to
EN1993:1-4)
Laghi, V., Palermo, M., Veljkovic, M., Gasparini, G., Trombetti, T., “Assessment of design mechanical parameters
and partial safety factors for Wire-and-Arc Additive Manufactured stainless steel”, Engineering Structures, 2020.

56. Structural design guidelines
Best-fit Normal / Log-normal distribution:
•Characteristic value corresponding to
the 5% fractile
•ULS Design value corresponding to
the 0.1% fractile
AnnexD of Eurocode0:
•
•
• exp( )
k y n y
X m k s   ,
exp( )
d y dn y
X mks  k
m
d
X
X

Laghi, V., Palermo, M., Veljkovic, M., Gasparini, G., Trombetti, T., “Assessment of design mechanical parameters
and partial safety factors for Wire-and-Arc Additive Manufactured stainless steel”, Engineering Structures, 2020.
Stainlesssteel308Lsi

57. Design values from tested coupons
Laghi, V., Palermo, M., Veljkovic, M., Gasparini, G., Trombetti, T., “Assessment of design mechanical parameters
and partial safety factors for Wire-and-Arc Additive Manufactured stainless steel”, Engineering Structures, 2020.
HighestCOVforyielding
andultimatestrength
(D)and ultimate
strength(T)
Stainlesssteel308Lsi

58. Design values from tested coupons
5% and 0.1% fractilesfrom
best-fit Log-normal distribution
Calibrated values
according to EC0
EC3
recommendations
f
y,5%f
y,0.1%f
y,5%/ f
y,0.1%f
ykf
yd 
m1
T321296 1.08 310301 1.24
1.10L305279 1.09 297283 1.20
D353309 1.14 343309 1.27
f
t,5%f
t,0.1%f
t,5%/ f
t,0.1%f
tkf
td 
m2
T469408 1.15 443424 1.43
1.25L533508 1.05 532517 1.09
D509441 1.16 494443 1.30
Yielding
stress
Ultimate
tensile stress
Laghi, V., Palermo, M., Veljkovic, M., Gasparini, G., Trombetti, T., “Assessment of design mechanical parameters
and partial safety factors for Wire-and-Arc Additive Manufactured stainless steel”, Engineering Structures, 2020.
ForTspecimens=>
Smallersamplesize
n=6coupledhigh
largeCOVleadstothe
highestpartialfactor
forUTS=1.43
Stainlesssteel308Lsi

59. Structural design guidelines
Yielding stressUltimate tensile strengthYoung’smodulus
f
ykf
yd
m1f
tk
f
td
m2
E
lbE
ub
[MPa][MPa] [MPa] [MPa] [GPa] [GPa]
WAAM-T3103001.244454251.4395 115
WAAM-L3002851.205305151.09105 165
WAAM-D3453101.274954451.30155 380
Stainlesssteel308Lsi

60. Structural design guidelines: design sheets

61. Proposed Protocol for tensile testing of WAAM
coupons
PROPOSED
PROTOCOL
Acquisition of
relevant
information
Setof standard
tensile tests
Data from the
producer
Ad-hoc
measures
ASTM E8/E8M

62. Protocol for tensile testing of WAAM couponsSET OF TENSILE
TESTS
Group 1: Tests on
machinedspecimens
90°
45°
0°
Group 2: Tests on
as-builtspecimens
90°45°
0°

63. Standards for mechanical characterization

64. Standards for mechanical characterization

65. THE TUBULAR SANDWICH CROSS-SECTION
•TSisatubularcrosssectionshavinga
internalfillforincreasedstructural
performances. Main geometrical
parameters:
•Dext,Dint,text,tint,tw,Nw,lw/t
•AFirstcataloguedevelopedusingRihno
parametricdesignalgorithmproviding
maininertiaparameters:
•A,J,r,…
•tisfixedforallwalls
•Somepossibleapplications:
•Three-likecolumns
•Offshorejackets
•HighrisebuildingsD
ext
t
TS CHS
CATALOGUE OF Sandwich cross-section
NAME
D
ext,D
int
[mm]
t
[mm]
N
w
[-]
l
w/t
[-]
CLASSFOR BUCKLING
TS_640_560_32 560 4 32 31 Class1
TS_800_720_40 720 4 40 31 Class1
TS_880_800_44 800 4 44 31 Class1
TS_960_880_48 880 4 48 31 Class1
TS_1000_800_48 800 4 48 33 Class1
ext
int
w
Case study 1: catalogue of uniform thickness TS

66. TS cross-sectionTS FE model mesh CHS FE model mesh CHS cross-section 2mm
1mm
4mm
Radialpressure
Structuralstrength CHS TS TS/CHS
AxialTension[kN] 926 926 1
Bending[kNm] 16.9 14.2 0.84
GlobalEulerbuckling[kN] 828 697 0.84
Radialbucklingpressure[MPa]2 1.08 1.852
APPLIED LOADS
Wall thickness is larger for
external cylinder walls
THE TUBULAR SANDWICH CROSS-SECTION
Case study 2: optimized offshore tubular elements

67. Uniform TS for three-like structures

68. WAAM TS : fabrications
AITTIP-2023
TS of 8 mm
nominal
thickness wall
TS of 4 mm
nominal
thickness wall

69. Computational structural design
INITIAL
DATASET
•Boundary conditions
•Applied loads
INITIAL
GEOMETRY
TOPOLOGY
OPT
STRUCTURAL
VERIFICATION
PARAMETRIC DESIGN
•Minimum weight
•Displacement constrained
STRUCTURAL
SOLUTIONS
MANUFACTURING
CONSTRAINTS
WAAM ORTHOTROPIC
MODEL

70. Computational structural design
Bruggi, M., Laghi, V., Trombetti, T., “Simultaneous design of the topology and build orientation of Wire-and-Arc
Additively Manufactured structural elements”, Computers and Structures, 2021.
TOPOLOGY OPTIMIZATION
FORWAAMPLANAR
ELEMENTS
Constraint:
DISPLACEMENT
Objective function:
MINIMUM WEIGHT
Variables:
DENSITY FIELD
PRINTING DIRECTION

71. Simply-supported 2D plate with concentrated vertical load at mid-span
Different optimal layouts depending on the printing direction (T,L,D) vs. isotropic
grade 304L
Computational structural design
Bruggi, M., Laghi, V., Trombetti, T., “Simultaneous design of the topology and build orientation of Wire-and-Arc
Additively Manufactured structural elements”, Computers and Structures, 2021. Grade 304 L WAAM
Grade 304L
WAAM-L
WAAM-T
WAAM-D
The optimal printing direction was
detected at 42°, for which the maximum
material reduction was reached (for a
given required stiffness)

72. Computational structural design
The final solution (which
encompasses all possible
loading conditions) has an
overall 30% weight reduction
Improved structural
performances with respect to
the traditional IPE300
3D Topology optimization from an IPE300 profile
(displacement-constrained)
Multiple loading cases applied
Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Exploration of structural designs through topology optimization using
metal 3D printing in construction”, International Conference on Additive Manufacturing (ICAM), November 2021.

73. WAAM
PROCESS
Experimental
characterization
Structural design
guidelines
Computational
structural design
Experimental
characterization
Structural design
guidelines
Orthotropic
material model
Computational
structural design
Research outline
DOT
-
BY
-
DOT
PRINTING

74. WAAM –
DOT-BY-DOT
PRINTING
EXPERIMENTAL
CHARACTERIZATION
STRUCTURAL DESIGN
GUIDELINES
COMPUTATIONAL
STRUCTURAL DESIGN

75. Issues to be
addressed
Influence of the process parameters and
build angle on the mechanical and
microstructural properties
Update of the current structural building
codesfor WAAM-produced rods
Definition of a new computational design
approach for WAAM-produced diagrid
columns

76. Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Girelli, V.A., Ceschini, L., Trombetti, T., “Mechanical response of dot-by-dot
wire-and-arc additively manufactured 304L stainless steel bars under tensile loading”, Construction and Building Materials,
125925, 2022.
dot –
45
dot –
10
dot
–0
z
z
z
Influence of the build angle Geometrical irregularitiesAnisotropicmechanical
properties
Influence of the nodal region
Dot-by-dot WAAM: the challenges

77. Material characterization: overview
Geometrical characterization: volumetric
measurements and 3D scanning
Microstructuralanalysis with EBSD and
XRD
Mechanicaltensile, bending and
compression tests on bars, nodes and unit
cells
LVDTand optical-basedmonitoringsystem
(DIC) to acquire full field of strain (both
longitudinal and transversal).
Tested materials: stainless steel 304L , carbon
steel ER70S-6
Carbon steelER 70S-6
Stainlesssteel308LSi
WAAM set-up @UNIFI
WAAM set-up @ MX3D

78. Stainlesssteelbarsof 6mm nominaldiameter
manufacturedby MX3D usingWAAM CMT process
Geometricalcharacterization
Microstructuralcharacterization
Mechanical characterization of single bars:
Tensile tests at three different build angles (e.g., 0°, 10°, 45°)
Three-point bending tests in the elastic field considering three
different build angles (e.g., 0°, 10°, 45°)
Compression/buckling tests at three different build angles (e.g., 0°,
10°, 45°)
Mechanical characterization of X bars:
Tensile tests on X bars at three different build angle (e.g., 10°, 20°,
30°)
Mechanical characterization of lattice cells
Experimental characterization of dot-by-dot WAAM
Single bars Cross X bars
Lattice cells

79. 3D model from scanningacquisition on
one as-built specimen (on 40 millions
points)
Detailed study of the cross-sectional
variation along the length of the
specimen
Detailed study of the lack of
straightness along the length of the
specimen
r
z
d
n
z
i
H
n
H
real
d
real
z
L
y
L
x
c
real
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Girelli, V.A., Ceschini, L. Trombetti, T., “Mechanical response of dot-by-dot wire-and-arc additively
manufactured 304L stainless steel bars under tensile loading." Construction and Building Materials, 2022.
Geometrical characterization from 3D scan
82/60

80. Detrimental effect of the higher
build angle (e.g., 45°) in the
geometrical irregularities
Higher values of eccentricity +30%
on average and +15% on maximum
of dot-45 with respect to dot-0
dot-0: e
mean=0.43mm; e
max=0.92 mm
dot-45: e
mean=0.55mm; e
max=1.12mm
Higher mean diameter of dot-45
(6.05 mm) with respect to dot-0 (5.77
mm), with lower dispersion
dot-0
dot-45
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Girelli, V.A., Ceschini, L. Trombetti, T., “Mechanical response of dot-by-
dot wire-and-arc additively manufactured 304L stainless steel bars under tensile loading." Construction and Building
Materials,. 2022
Geometrical characterization from 3D scan
z
??????=??????
�
2
+??????
�
2
Diameter distributionsEccentricity distributions

81. Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Girelli, V.A., Ceschini, L. Trombetti, T., “Mechanical response of dot-by-
dot wire-and-arc additively manufactured 304L stainless steel bars under tensile loading." Construction and Building
Materials,. 2022
Microstructural characterization from 3D scan
3D optical microscopy showing the
overall microstructure. In case of
dot-0 and dot-10 (a, b), layer
boundaries are almost
perpendicular to the building
direction while a slight inclination
can be observed for dot-45 bars (c)
Colour microscopy showing
epitaxial growth of columnar grains
crossing-over layers. Yellow and
white dashed lines underline layer
boundaries and epitaxial grains,
respectively.The formation of
highly-oriented large columnar
grains crossing-over layers is
promoted (d, e, f)

82. Mechanical behavior in tension: problem formulation
Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.

83. Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.
Tensile tests on 29 as-built stainless steel(welding wire grade ER308LSi)specimens printed at three different built
angles: straight (0°), inclined at 10°and at 45°, having 6mm nominal diameter
n-a= nozzleangle
b-a= buildangle
Mechanical behavior in tension: the tested specimens

84. Dot-0 specimens
Mechanical behavior in tension: effective stress-strain
Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.

85. Dot-10 specimens
Mechanical behavior in tension: effective stress-strain
Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.

86. Dot-45 specimens
Mechanical behavior in tension: effective stress-strain
Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.

87. Laghi, V., Palermo, M., Silvestri, S., Gasparini, G., Trombetti, T., “Experimental behavior of Wire-and-Arc Additively
Manufactured stainless steel rods”, Proceedings in Eurosteel conference, September 2021.
High influence on the printing
inclination in terms of both Young’s
modulus and strength values.
Very low Young’s modulusvalues
(from 137 GPa to 98 GPa on average)
Higher overstrengthratio
(ultimate/0.2% proof) with respect to
the continuous printing, suggesting a
higher hardening phase, possibly
induced by geometrical effects
WAAM –T
(continuos)
Mechanical behavior in tension: key effective parameters

88. Best-fit Normal / Log-normal distribution:
•Characteristic value corresponding to
the 5% fractileconsidering different
CI
•Design value corresponding to the 0.1%
fractileconsidering different CI
AnnexD of Eurocode0:
•
•
• exp( )
k y n y
X m k s   ,
exp( )
d y dn y
X mks  k
m
d
X
X

Mechanical behavior in tension: design values

89. Mechanical behavior in tension: design values

90. Mechanical behavior in tension: partial safety factors

91. ADVANCED FE SIMULATIONS
Mechanical behavior in bending: problem formulation
PVW
Laghi, V., Girelli, V. A., Gasparini, G., Trombetti, T., & Palermo, M. (2024). Investigationon the elasticflexuralstiffnessof dot-by-dot wire-
and-arcadditivelymanufacturedstainlesssteelbars. Engineering Structures, 306, 117680.

92. Three-point bending testson 10 as-built stainless steel(welding wire grade
ER308LSi)bars of 6mm nominal diameter to evaluate the flexural stiffness
Laghi, V., Girelli, V. A., Gasparini, G., Trombetti, T., & Palermo, M. (2024). Investigationon the elasticflexuralstiffnessof dot-by-dot wire-
and-arcadditivelymanufacturedstainlesssteelbars. Engineering Structures, 306, 117680.
Mechanical behavior in bending: experimental tests set-up ()
()
nn
real real
EJ
EJ




93. Along-the-lengthvariationof moment of inertiaJ and cross sectionarea A
Mechanical behavior in bending: moment of inertia
Laghi, V., Girelli, V. A., Gasparini, G., Trombetti, T., & Palermo, M. (2024). Investigationon the elasticflexuralstiffnessof dot-by-dot wire-
and-arcadditivelymanufacturedstainlesssteelbars. Engineering Structures, 306, 117680.
96/60

94. Mechanical behavior in bending: flexural Young’s modulus
97
The flexural elastic modulus as
evaluated according to the
three proposed approaches is
approximately equal, on
average, to 113 GPa.
Such value if on average equal
to 0.85 the average tensile
elastic modulusas obtained
from tensile tests (137 GPa)
This result indicates an
anisotropic behaviour
Laghi, V., Girelli, V. A., Gasparini, G., Trombetti, T., & Palermo, M. (2024). Investigationon the elasticflexuralstiffnessof dot-by-dot wire-
and-arcadditivelymanufacturedstainlesssteelbars. Engineering Structures, 306, 117680.
97/60

95. Mechanical behavior in compression: problem formulation
v
0/L=equivalent imperfection parameterExtended Perry-Robertsonformulation
98/60

96. Mechanical behavior in compression: problem formulation
Stiffnesscurves Bucklingcurves

97. Compression testson 17 as-
built stainless steel(welding
wire grade ER308LSi)
specimens with different
lengths (e.g.,240mm, 120mm,
80mm, 60mm) and 6mm
nominal diameter
Interpretation of the results
based on the flexural stiffness
estimated from bending tests.
Effective Buckling length factor
b=0.9
Mechanical behavior in compression: experimental testsC01 C02 C03 C04
C
0
1
-
1
C
0
1
-
2
C
0
1
-
3
C
0
2
-
1
C
0
2
-
2
C
0
2
-
3
C
0
2
-
4
C
0
3
-
1
C
0
3
-
2
C
0
3
-
3
C
0
3
-
4
C
0
3
-
5
C
0
3
-
6
C
0
4
-
1
C
0
4
-
2
C
0
4
-
3
C
0
4
-
4
dot-1
dot-2
dot-3
dot-4
dot-5
dot-6
dot-7
dot-8

98. Mechanical behavior in compression: geometry
0.1%
0.2%-2%

99. L=240 mm
??????=2,25
L=60 mm
??????=0,56
Experimental results: force vs displacement curves

100. Experimental results: N
crvs slenderness
Mean-2std values are very
much lower than those
according to our current EC3
buckling curves

101. Planar X bars: problem formulation

102. Planar X bars: expected modes of failureNode
rupture
Ruptureat
intersection
Bar
rupture

103. Planar X bars: the tested specimens
43 X bars tested with 3
different inclination angles
(e.g., 15 at 10°,15 at30°,13
at 45°)
Tensile tests applying the
tensile force on the
straight bar (A) or inclined
bar (B)
All specimens having d
n=6
mm, L
n=250 mm
A
B
A
BA
B

104. Planar X bars: geometrical properties
Specimen-to-specimen variability
Specimen d
eff [mm]
X10 5.66 ±0.02
X20 5.67 ±0.04
X30 5.72 ±0.03

105. Planar X bars: Microstructuralcharacterization
X30 sample
Metallographic analyses showed
grains growing epitaxially by
following the building direction
metallographic analyses of
fracture regions highlighting
different grain orientations

106. Planar X bars: tensile tests set-up

107. Planar X bars: tensile tests force-displacement
curves

108. Planar X bars: modes of failureNode
rupture
Ruptureat
intersection
Bar
rupture Node
rupture
Ruptureat
intersection
Bar
rupture Node
rupture
Ruptureat
intersection
Bar
rupture
Node
Intersection
Bar

109. Planar X bars: ultimate strength vs angle
f
u
[
MPa
]
530
350
180
Single barsfrom tensile tests
705
Significant detrimental effect of the
build angle for tests on rod B on the
ultimate strength, from 11,27 kN
(RodB-X10) to 8,40 kN(RodB-X30).
Slight strength reduction of ultimate
strength for rod Afor increasing
build angles, from 12,11 kN(RodA-
X10) to 11,21 kN(RodA-X30).
Typical mode of failure is the
rupture in the nodal region.

110. Planar X bars: ultimate strength X vs single bars

111. EUROPEAN
STANDARD CODE
DESIGN ASSISTED
BY TESTING
NEW CODE PROVISIONS
FOR WAAM
•Characteristic and
design values for
strength
•Pre-definedsafety
factors
•Estimationof the
design values and
safety factors from
experiments
•Characteristic and design
values for strength based
on the printing build
angle
•Updated safety factors
accounting for the
geometrical and
mechanical variability
Structural design guidelines

112. Structural design guidelines

113. Full Integration of:
basic principles of structural design
(efficient structural solutions)
computational design & topology
optimization
printing process features in terms of
capabilities and limitations
Advanced FEM simulations
Laghi, V., Palermo, M., Bruggi, M., Gasparini, G., Trombetti, T., “Blended structural optimization for wire-and-arc additively manufactured
beams”, Progress in Additive Manufacturing, 2022.
Structural design for AM

114. INITIAL
DATASET
•Boundary conditions
•Applied loads
INITIAL
GEOMETRY
GLOBAL
SHAPE OPT
TOPOLOGY
OPT
STRUCTURAL
VERIFICATION
PARAMETRIC DESIGN
•Minimum weight
•Maximum allowable
utilization factor
STRUCTURAL
SOLUTIONS
MANUFACTURING
CONSTRAINTS
Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Computational design and manufacturing of a half-scaled 3D-
printed stainless steel diagrid column”, Additive Manufacturing, 2020.
WAAM MATERIAL +
GEOMETRICAL
PROPERTIES
Computational structural design

115. Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Computational design and manufacturing of a half-scaled 3D-
printed stainless steel diagrid column”, Additive Manufacturing, 2020.
Computational structural design

116. Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Computational design and manufacturing of a half-scaled 3D-
printed stainless steel diagrid column”, Additive Manufacturing, 2020.
Diagrid column Fabrication @ MX3D

117. ??????= 1,5
??????= 2
??????= 3
Conventionalpole
10 %
47 %
68 %
Performances
FABRICATION
WEIGHT REDUCTION
Laghi, V., & Gasparini, G. (2023, October). Explorations of efficient design solutions for Wire-and-Arc Additive
manufacturing in construction. In Structures (Vol. 56, p. 104883). Elsevier.
TU Braunschweig 2021
Applications: WAAM Lattice Pole (patented)
LATTICE POLE CROSS SECTION

118. Extremity of
the loading
machine
U-shaped box
M30 connection bolt
DIC
camera
CSB device
Test machine
Point A
Point C Dot-by-dot WAAM CSB
Applications: WAAM dissipative CSB connections for steel frames
CIRCULARWELD Project
Unit cubiccell
Palermo, M., Laghi, V., Silvestri, S., Gasparini, G., & Trombetti, T. (2022, September). Crescent Shaped Brace Devices to
Strengthen Pinned Beam-Column Connections via Semi-rigid CSB Joints. InWorld Conference on Seismic Isolation

119. FOCUS: WAAM optimized beams

120. SIMP ESO/BESO Ground structure
Grasshopper plug-in
tOpos Ameba Peregrine
SupportsLoads Slenderness
•Doubly pinned
•Doubly clamped
•Concentrated force
•Distributed load
•1/4
•1/6
•1/8
WAAM
optimized
beams

121. SIMP ESO/BESO Ground structure
Grasshopper plug-in
tOpos Ameba Peregrine
WAAM
optimized
beams

122. Slenderness 1/8; L = 2.4 m
Load Distributed; 30kN/m
Supports Doubly pinned
WAAM optimized beams
CASE 1

123. Slenderness 1/8; L = 2.4 m
Load Distributed; 30kN/m
Supports Doubly pinned
WAAM optimized beams
CASE 1

124. WAAM optimized beams
CASE 2
Slenderness 1/8; L = 2.4 m
Load Point; 72kN
Supports Doubly pinned

125. WAAM optimized beams
CASE 2
Slenderness 1/8; L = 2.4 m
Load Point; 72kN
Supports Doubly pinned

126. WAAM optimized beams
CASE 3
Slenderness 1/6; L = 1.8 m
Load Distributed; 30kN/m
Supports Doubly pinned

127. WAAM optimized beams
CASE 3
Slenderness 1/6; L = 1.8 m
Load Distributed; 30kN/m
Supports Doubly pinned

128. WAAM optimized beams
CASE 4
Slenderness 1/6; L = 1.8 m
Load Point; 56kN
Supports Doubly pinned

129. WAAM optimized beams
CASE 4
Slenderness 1/6; L = 1.8 m
Load Point; 56kN
Supports Doubly pinned

130. WAAM optimized beams
CASE 5
Slenderness 1/4; L = 1.2 m
Load Distributed; 30kN/m
Supports Doubly pinned

131. WAAM optimized beams
CASE 5
Slenderness 1/4; L = 1.2 m
Load Distributed; 30kN/m
Supports Doubly pinned

132. WAAM optimized beams
CASE 6
Slenderness 1/4; L = 1.2 m
Load Point; 36kN
Supports Doubly pinned

133. WAAM optimized beams
CASE 6
Slenderness 1/4; L = 1.2 m
Load Point; 36kN
Supports Doubly pinned

134. WAAM optimized beams
CASE 7
Slenderness 1/8; L = 2.4 m
Load Distributed; 30kN/m
Supports Doubly clamped

135. WAAM optimized beams
CASE 7
Slenderness 1/8; L = 2.4 m
Load Distributed; 30kN/m
Supports Doubly clamped

136. WAAM optimized beams
CASE 8
Slenderness 1/8; L = 2.4 m
Load Point; 72kN
Supports Doubly clamped

137. WAAM optimized beams
CASE 8
Slenderness 1/8; L = 2.4 m
Load Point; 72kN
Supports Doubly clamped

138. WAAM optimized beams
CASE 9
Slenderness 1/6; L = 1.8 m
Load Distributed; 30kN/m
Supports Doubly clamped

139. WAAM optimized beams
CASE 9
Slenderness 1/6; L = 1.8 m
Load Distributed; 30kN/m
Supports Doubly clamped

140. WAAM optimized beams
CASE 10
Slenderness 1/6; L = 1.8 m
Load Point; 56kN
Supports Doubly clamped

141. WAAM optimized beams
CASE 10
Slenderness 1/6; L = 1.8 m
Load Point; 56kN
Supports Doubly clamped

142. WAAM optimized beams
CASE 11
Slenderness 1/4; L = 1.2 m
Load Distributed; 30kN/m
Supports Doubly clamped

143. WAAM optimized beams
CASE 11
Slenderness 1/4; L = 1.2 m
Load Distributed; 30kN/m
Supports Doubly clamped

144. WAAM optimized beams
CASE 12
Slenderness 1/4; L = 1.2 m
Load Point; 36kN
Supports Doubly clamped

145. WAAM optimized beams
CASE 12
Slenderness 1/4; L = 1.2 m
Load Point; 36kN
Supports Doubly clamped

146. Blended optimization
1.Typical slenderness of I-type beams in space frames
2.Consideration of the true nature of steel connections
3.Multiple load cases

147. Blended optimization
Slenderness 1/15; L = 4.5 m
Load Point; 135kN
Supports Simply supported beam vs doubly pinned
25.4%
53.5%
Definition of the boundary conditions

148. Slenderness 1/15; L = 4.5 m
Load Distributed; 30kN/m –45kN/m –60kN/m
Supports Simply supported beam
52.4%
21.8%
11.0%
Blended optimization
Definition of the load value

149. Slenderness 1/15; L = 4.5 m
Load Multiple load cases
Supports Simply supported beam –rod imposed
43.4%
30.1%
41.6%
28.2%
28.2%
Blended optimization
Multiple loading conditions

150. Blended optimization
Final beam –21% weight reduction

151. Material: S355
Structural verification

152. Material: S355
Structural verification

153. Material: S355
Structural verification

154. Material: S355
Structural verification

155. 0
2
4
6
8
10
12
14
16
18
1 2 3 4
Displacement Uz [mm]
Load Case
Comparison of displacement in local-z direction results
Maximum displacement Uz; IPE300
Maximum displacement Uz; optimized
beam
Structural verification

156. 0
50
100
150
200
250
300
350
400
1 2 3 4
Von Mises stress [MPa]
Load case
Comparison of Von Mises stress results
Maximum Von Mises stress; optimized beam
Maximum Von Mises stress; IPE300
Structural verification

157. Failure criteria:
Yielded
XLateral-torsional buckling
XLocal buckling
0
50
100
150
200
250
300
350
400
450
500
0,0 4,8 9,5
14,3 19,1 23,8 28,4 33,0 37,6 42,3 46,9 51,6 56,2 60,9 65,5 70,2 74,8 79,4 84,0 88,6 93,2 97,8
102,4 107,0 111,6 116,2 120,7 125,3 129,8 134,4 138,9 143,4 147,9 152,4 156,8 161,3 165,7 170,1 174,5 178,8 183,1 187,4 191,6 195,8 199,8 203,9 207,8 211,8 215,6 219,5 223,3
FORCE [KN]
DISPLACEMENT [MM]
Pushover force-displacement graph
Lateral torsional buckling:
250.07kN
Local buckling:
377.45kN
Maximum:
434.42kN
Reference value
Design at SLS: 135kN
Structural verification

158. Additional considerations
using WAAM stainless steel
material model
•Orthotropic material
L
D
T
Structural verification

159. 0 0,5 1 1,5
U3
MISES
Maximum value of the parameter relative to the linear-elastic isotropic steel
benchmark
Parameter
Comparison of isotropic structural steel with orthotropic
WAAM steel results
Linear elastic orthotropic WAAM
Linear elastic isotropic steel
Isotropic steel
Isotropic steel
Orthotropic WAAM
Orthotropic WAAM
Structural verification

160. WAAM-L
WAAM-T
WAAM-D
Structural verification
WAAM-L
WAAM-T
WAAM-D

161. 0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
WAAM-L WAAM-T WAAM-D
Results normalized to WAAM
-
L results
Material direction
Relative results of elasto-plastic material definition relative
to WAAM-L
Maximum displacement in
z-direction
Maximum Von Mises stress
Structural verification

163. FOCUS: WAAM lattice structures

164. Dot-by-dot printing

165. dot –45
dot –10
dot –0
z
z
z
Influence on the build angle Geometrical irregularitiesAnisotropicmechanical
properties
Laghi, V., Palermo, M., Tonelli, L., Gasparini, G., Girelli, V.A., Ceschini, L., Trombetti, T., “Mechanical response of dot-by-dot
wire-and-arc additively manufactured 304L stainless steel bars under tensile loading”, Construction and Building Materials,
125925, 2022.
Dot-by-dot printing

166. Possibilitytoprinthigh-efficiencylattice
elementswithareductioninweightupto
90%
Longprintingtime
Dot-by-dot printing

167. MICRO-SCALE MACRO-SCALEMESO-SCALE
WAAM lattice elements

168. 2018: MX3D
2021: 3D Pioneers Challenge
2021: TU Braunschweig
2022: Italianpatent
Dot-by-dot printing

169. Standard
pole
WAAM lattice
pole
WAAM lattice pole

170. ??????= 1,5
??????= 3
??????= 2
s= 4 mm s= 6 mm
WAAM lattice pole

171. Definition of the global shapes
WAAM lattice pole
Geometricalparameters:
•Distribution/variationofexternaldiameters
•Distributionofcontrolsections

172. Definition of the global shapes
Geometricalparameters:
•Distribution/variationofexternaldiameters
•Distributionofcontrolsections
•TYPE1:constantdistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE2:constantdistributionofexternaldiameters,variable
distributionofcontrolsections
•TYPE3:variabledistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE4:variabledistributionofexternaldiameters,variable
distributionofconstrolsections
WAAM lattice pole

173. Definition of the global shapes
Geometricalparameters:
•Distribution/variationofexternaldiameters
•Distributionofcontrolsections
•TYPE1:constantdistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE2:constantdistributionofexternaldiameters,variable
distributionofcontrolsections
•TYPE3:variabledistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE4:variabledistributionofexternaldiameters,variable
distributionofconstrolsections
WAAM lattice pole

174. Definition of the global shapes
Geometricalparameters:
•Distribution/variationofexternaldiameters
•Distributionofcontrolsections
•TYPE1:constantdistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE2:constantdistributionofexternaldiameters,variable
distributionofcontrolsections
•TYPE3:variabledistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE4:variabledistributionofexternaldiameters,variable
distributionofconstrolsections
WAAM lattice pole

175. Definition of the global shapes
Geometricalparameters:
•Distribution/variationofexternaldiameters
•Distributionofcontrolsections
•TYPE1:constantdistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE2:constantdistributionofexternaldiameters,variable
distributionofcontrolsections
•TYPE3:variabledistributionofexternaldiameters,constant
distributionofcontrolsections
•TYPE4:variabledistributionofexternaldiameters,variable
distributionofconstrolsections
WAAM lattice pole

176. WAAM lattice pole
Generation of virtualmodels
•Definitionofthe«atomizedsection»
•Repetitionofthesectionalongthepolelength
•Creationofthediagrid

177. ??????= 1,5
??????= 2
??????= 3
Weight reduction:
Conventionalpole
TYPE 1
10 %
49 %
72 %
10 %
48 %
71 %
10 %
47 %
68 %
10 %
45 %
65 %
WAAM lattice pole
TYPE 3
TYPE 2 TYPE 4

178. WAAM lattice pole
Structural analyses:
•Linear static analysis (Karamba3D, SAP2000)
•Non-linear static analysis (SAP2000)
•Linear buckling analysis (SAP2000)

179. WAAM lattice pole
Linear static analysis:
•Compressive design load equal to 20 kN
•Simply-supported constraints (hinge-roller)
•WAAM stainless steel material

180. ??????= 1,5
??????= 2
??????= 3
Utilizationfactor(U%)
Linear staticanalysis
Karamba3D
ConventionalpoleU% = 5
>> 100
>> 100
>> 100
>> 100
>> 100
>> 100
>> 100
>> 100
WAAM lattice pole

181. ??????= 1,5
??????= 2
??????= 3
Utilizationfactor(U%)
Linear staticanalysis
Karamba3D
ConventionalpoleU% = 5
WAAM lattice pole

182. Linear staticanalysis
SAP2000
ConventionalpoleU% = 5WAAM lattice pole
??????= 1,5 s = 4 mmU% = 78
??????= 1,5 s = 6 mmU% = 111
??????= 1,5 s = 4 mmU% = 85
??????= 1,5 s = 6 mmU% = 120
??????= 1,5 s = 4 mmU% = 101
??????= 1,5 s = 6 mmU% = 178
??????= 2s = 4 mmU% = 85
??????= 1,5 s = 6 mmU% = 72
TYPE 1 TYPE 2 TYPE 3 TYPE 4

183. 171
178
4 mm
6 mm
82
78
121
111
4 mm
6 mm
101
107
129
120
91
85
4 mm
6 mm
72
85
85
101
4 mm
6 mm
ComparisonKaramba3D –SAP2000
Karamba3D
Utilizationfactor(U%)
SAP2000
WAAM lattice pole

184. WAAM lattice pole
Non-linear static analysis:
•Incremental vertical compressive load
•Maximum allowable displacement of the top
section equal to 100 mm
•Simply-supported constraints (hinge-roller)
•WAAM stainless steel material

185. Non-linear staticanalysis
SAP2000
Linear staticanalysis20 kNWAAM lattice pole
TYPE 1 TYPE 2 TYPE 3 TYPE 4
??????= 1,5 s = 4 mm6,13 kN
??????= 1,5 s = 6 mm31,48kN
??????= 1,5 s = 4 mm3,17 kN
??????= 1,5 s = 6 mm14,28kN
??????= 1,5 s = 4 mm6,48kN
??????= 1,5 s = 6 mm27,37kN
??????= 2s = 4 mm2,92kN
??????= 1,5 s = 6 mm14,36kN

186. WAAM lattice pole
Linear buckling analysis:
•Unitary vertical compressive load
•Simply-supported constraints (hinge-roller)
•WAAM stainless steel material

187. Collapseload (NL-S)
Loads:
Critical load (L-B) 6 mm
31,48 kN
32,76 kN
4 mm
6,13 kN
6,18 kN
4 mm
3,17 kN
3,26 kN
6 mm
14,28 kN
14,68 kN
4 mm
5,95 kN
6,48 kN
6 mm
27,37 kN
30,92 kN
4 mm
2,92 kN
2,93 kN
6 mm
14,36 kN
14,59 kN
Comparisonlinear buckling–nonlinearstatic
SAP2000
WAAM lattice pole

188. •Workonthehyperbolicshape
•Forceamoreclampedconfiguration
•Impose a maximum allowablelengthof the single bars(to
avoidlocalbuckling)
•Absenceof horizontalhoopsatcontrol sections
•Barsintersections(diagridnodes) modelledashinges
•Excessivelengthof the single bars
Manufacturing issues
Modellingissues
Solution
Solution
WAAM lattice pole

190. •Possibility to print at various scales and different densities of the diagrid
•Only external diagrid
•3D diagrid (internal and external)
•Long printing time
•Manufacturing constraints
•Max 45°inclination of the bars (to maintain good properties)
•Limitation in maximum free length of the bars (to avoid local
buckling)
Fabrication of lattice elements

191. •Organization of the curves to guarantee the correct
order of printing of successive points
•Be sure to have 5 commands associated to each
printing point:false,true,wait, false, false
•Associate 5 positions in the space for each printing
point, corresponding to the commands and to the
offset between printing and waiting.
Fabrication of lattice elements

192. •Cold Metal Transfer (CMT) results in better quality of
the printed lattice
•High accuracy of the robotic system is requested
(point precision within 0.5 mm)
•Real-time monitoring reduces the error between ideal
and real layer height
•Fundamental printing parameters to set:
•Wire feed speed (Wfs)​
•Gas pre and post flow​
•Welding / waiting time​
Fabrication of lattice elements

193. MX3D, Amsterdam -2018
Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Computational design and manufacturing of a half-scaled 3D-printed stainless
steel diagrid column”, Additive Manufacturing, 2020.
Case study –WAAM diagrid column

194. MX3D, Amsterdam -2018
Laghi, V., Palermo, M., Gasparini, G., Trombetti, T., “Computational design and manufacturing of a half-scaled 3D-printed stainless
steel diagrid column”, Additive Manufacturing, 2020.
Case study –WAAM diagrid column

195. TU Braunschweig -2021
Case study –WAAM 3D diagrid

196. TU Braunschweig -2021
Case study –WAAM 3D diagrid

197. Dörrie, R., Laghi, V., Arrè, L., Kienbaum, G., Babovic, N., Hack, N., & Kloft, H., “Combined Additive Manufacturing Techniques for
Adaptive Coastline Protection Structures”, Buildings,2022.
TU Braunschweig -2022
Case study –FloWall