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Hybrid Wood and Steel System: Overstrength and Ductility. M.A.Sc Student: Carla Dickof Supervisor: Professor Stiemer, UBC; Professor Tesfamariam , UBC Okanagan FP innovations: Erol Karacabeyli Marjan Popovski. Project Description. Goal : - PowerPoint PPT Presentation
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Hybrid Wood and Steel System: Overstrength and Ductility
M.A.Sc Student: Carla DickofSupervisor: Professor Stiemer, UBC;
Professor Tesfamariam, UBC OkanaganFP innovations: Erol Karacabeyli
Marjan Popovski
Goal: Analyse and provide guidelines for the design of the hybrid seismic force resisting system, steel moment frames with infill wood shear walls
Hybrid System of Interest:• Hybridize steel and wood into a vertical seismic force resisting system.• Focus on steel moment frames with a wood infill wall system• Address material incompatibilities with special attention to hydroscopic
properties in wood• Provide values for equivalent static seismic design of system
Project Description
Hybrid System: Base Building
Building Plan Frame Elevation
Hybrid System: Parameters
Parameter Options
Infill Wall Types CLT shear walls Midply shear walls
Ductility Limited Ductility Ductile
Storeys 9 6 3Braced Bays One Bay 2 Bays 3 bays
Bracket Properties Gap between infill and steel frame
Infill Case 1 Infill Case 2 Infill Case 3
Bare Frame Design
• Steel moment frame to be designed based with NBCC ductility requirements
• Infill walls to be added and compare the response of the frame and the response of plain wood wallsDuctility Type
Steel Moment
Wood
Rd Ro Rd Ro
D 5.0 1.5
2.0 1.7MD 3.5 1.5
LD 2.0 1.3
Infill Walls: Midply Shear WallsMidply walls have higher strength compared to standard plywood shear walls• Nails in double shear• Nail head does not
pull through sheathing
• Increased nail edge distance
Failure of walls occurs through buckling of studs
Infill Walls: CLT WallsParallel to grain
Perpendicular to grain
ELASTIC PROPERTIESElastic 7800 MPa 4600 MPaShear 250 MPaSTRENGTHTension 16.5 MPaCompression 24 MPaCrushing 30 MPaShear 5.2 MPa
• Approximated as elastic perfectly plastic with plasticity model
• Elastic properties determined using composite theory
• Strength limits determined from product data
• Plain CLT systems show all deformation in connectors
• Confinement from surround frame may cause deformation in the panel
Pure Rocking Shear and RockingPure Shear
Connection between Wall and Frame• Nailed bracket
connection developed for CLT walls
• Bracket behaviour is independent in different directions
• Confinement also provided along edges of panel to provide confinement using “gap” elements
-40 -30 -20 -10 0 10 20 30 40
-50
-40
-30
-20
-10
0
10
20
30
40
50
PerpPara
Displacement (mm)
Forc
e (K
N)
0 0.01 0.02 0.03 0.04 0.050
100
200
300
400
500
600
700
Bas
e S
hear
(KN
)
Drift (mm/mm)
bare framemidply infillCLT infill
Effect of Infill Panel Type: Single Storey Single Bay Frame
Pushover Results
Effect of Gap Size between Infill Panel and Frame: Single Bay Single Storey Frame
Pushover Results
0 0.01 0.02 0.03 0.04 0.050
200
400
600
800
1000
1200
Bas
e S
hear
(KN
)
Drift (mm/mm)
no gapgap=3mmgap=10mmgap=20mmgap=50mmunconfinedbare frame
Effect of Moment Frame Ductility: 3 Storey Steel for all Infill Configurations
Pushover Results
0 0.05 0.10
1000
2000
3000
4000
Base
She
ar (K
N)
Drift (mm/mm)
Type D Frame
0 0.05 0.10
1000
2000
3000
4000
Drift (mm/mm)
Type LD Frame
plain CLT1 CLT2 CLT3Frame YieldPanel Yield
Effect of Number of Storeys: Limited Ductility Steel Moment Frames for all Infill Configurations
Pushover Results
0 0.05 0.10
1000
2000
3000
4000
5000
Base
She
ar (K
N)
Drift (mm/mm)
3 Storey Frame
0 0.05 0.10
1000
2000
3000
4000
5000
Drift (mm/mm)
6 Storey Frame
0 0.05 0.10
1000
2000
3000
4000
5000
Drift (mm/mm)
9 Storey Frame
plain CLT1 CLT2 CLT3Frame YieldPanel Yield
Pushover Results3 Storey Frame 9 Storey Frame6 Storey Frame
DuctileLim
ited Ductility
Comparison of Frame and Panel Yield for all Frames and Infill Configurations
1 2 3800
1300
1800
2300
2800
3300
996.6Base
She
ar (K
N)
1 2 3800
1300
1800
2300
2800
3300
1223.8
1 2 3800
1300
1800
2300
2800
3300
1108.9
1 2 3800
13001800230028003300
1032.2
Infilled Bays
Base
She
ar (K
N)
1 2 3800
13001800230028003300
1132
Infilled Bays1 2 3
80013001800230028003300
977
Infilled Bays
1659.6
1958.52221.7
3041.1 2613.4 2736.1
977800
1800
2800
1 2 3Infilled Bays
frame yield panel yield bare frame yield
Overstrength (Ro or Ω) • Overstrength is the ratio of the
design load to the ultimate load of the system
• Looking at the innate overstrength in this type of system, the design load is taken as the load at first yield
Ductility (Rd or µT)• Ductility is the ratio of the
displacement at the ultimate load to the displacement at failure
• Failure is taken as an 80% reduction in strength after the ultimate load has been acheived according to FEMA P695
NBCC Seismic Factor Definition
Ductility Factor for all Frames
NBCC Seismic Factors
3 6 90.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.07.8
6.9
4.8
1.62.1
2.63.0
1.8 1.6
2.71.9 1.6
3.7
2.2 1.9
3.5
2.31.9
3.22.6
2.2
3.7
2.82.2
D bare frame LD bare frameD + 1 bay infill LD + 1 bay infillD + 2 bay infill LD + 2 bay infillD + 3 bay infill LD + 3 bay infill
Frame Storeys
Duc
tility
3 6 90.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
2.01.7 1.8
1.3
1.82.02.0 1.9 2.0
1.2
2.02.3
2.2
1.82.1
1.1
2.02.3
2.01.8
2.1
1.1
2.02.3
D bare frame LD bare frameD + 1 bay infill LD + 1 bay infillD + 2 bay infill LD + 2 bay infillD + 3 bay infill LD + 3 bay infill
Frame Storeys
Ove
rstr
engt
h
Overstrength Factors for all Frames
NBCC Seismic Factors
Future Work
• FEMA P695 guidelines for dynamic analysis• Partial Incremental dynamic analysis
– 22 ‘Far-Field’ ground motions
Our supporters at NewBuildS through NSERC and Canadian Steel Institute of Steel Construction
Thanks to everyone at FPInnovations, with special thanks to Dr. Popovski and Prof. Karacabeyli, industrial advisors to the project
Special thanks to the supervisors Dr. Stiemer and Dr.Tesfamariam from the University of British Columbia
Acknowledgements to UBC grad students: Yalda Khorasani, Mathieu Angers, Hassan Pirayesh, Carla Dickof, Caroline Villiard, Benedikt Zeisner.
Acknowledgements