Hybrid Wood and Steel System:
Overstrength and Ductility
M.A.Sc Student:
Supervisor:
FP innovations:
Carla Dickof
Professor Stiemer, UBC;
Professor Tesfamariam, UBC Okanagan
Erol Karacabeyli
Marjan Popovski
Project Description
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
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
3
One Bay
2 Bays
3 bays
Braced Bays
Bracket
Properties
Infill Case 1
Gap between infill and steel frame
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 walls
Ductility
Type
Steel
Moment
Rd Ro
D
5.0
1.5
MD
3.5
1.5
LD
2.0
1.3
Wood
Rd
Ro
2.0
1.7
Infill Walls: Midply
Shear Walls
Midply 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 Walls
• 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
Pure Shear
Parallel to Perpendicular
grain
to grain
ELASTIC PROPERTIES
Elastic
7800 MPa 4600 MPa
Shear
250 MPa
STRENGTH
Tension
16.5 MPa
Compressio 24 MPa
n
Crushing
30 MPa
Shear
5.2 MPa
Shear and Rocking
Connection between
Wall and Frame
• Nailed bracket
connection developed
for CLT walls
50
Perp
Para
40
30
• Bracket behaviour is
independent in
different directions
• Confinement also
provided along edges of
panel to provide
confinement using
“gap” elements
Force (KN)
20
10
0
-40 -30 -20 -10
-10 0
10
20
-20
-30
-40
-50
Displacement (mm)
30
40
Pushover Results
700
Base Shear (KN)
600
500
400
300
200
bare frame
midply infill
CLT infill
100
0
0
0.01
0.02
0.03
Drift (mm/mm)
0.04
Effect of Infill Panel Type: Single Storey Single Bay Frame
0.05
Pushover Results
1200
Base Shear (KN)
1000
800
no gap
gap=3mm
gap=10mm
gap=20mm
gap=50mm
unconfined
bare frame
600
400
200
0
0
0.01
0.02
0.03
Drift (mm/mm)
0.04
Effect of Gap Size between Infill Panel and Frame: Single Bay
Single Storey Frame
0.05
Pushover Results
Type D Frame
Base Shear (KN)
4000
Type LD Frame
4000
3000
3000
2000
2000
1000
1000
0
0
0.05
Drift (mm/mm)
0.1
0
0
plain
CLT1
CLT2
CLT3
Frame Yield
Panel Yield
0.05
Drift (mm/mm)
0.1
Effect of Moment Frame Ductility: 3 Storey Steel for all Infill
Configurations
Pushover Results
3 Storey Frame
Base Shear (KN)
5000
6 Storey Frame
5000
9 Storey Frame
5000
4000
4000
4000
3000
3000
3000
2000
2000
2000
1000
1000
1000
0
0
0.05
Drift (mm/mm)
0.1
0
0
0.05
Drift (mm/mm)
0.1
0
0
plain
CLT1
CLT2
CLT3
Frame Yield
Panel Yield
0.05
Drift (mm/mm)
Effect of Number of Storeys: Limited Ductility Steel Moment
Frames for all Infill Configurations
0.1
Pushover Results
3 Storey Frame
Base Shear (KN)
Ductile
3300
2800
2300
1800
1300
Base Shear (KN)
Limited Ductility
800
2286
2409.4
2016
1847.2 2016
996.6
2409.4
6 Storey Frame
3300
2800
2300
1800
1300
800
1
2
3
3300
2707.7 3261.9
2800
2349.2
2300
1800
2055.9
1796.2 1923.5
1300
1032.2
800
1
2
3
Infilled Bays
9 Storey Frame
3300
2807.7
2703.2
2800 2997.6
2900.8
2300
2515.7
2352.5
2175
2211.3
18001993.3
1223.8
1300
1108.9
800
1
2
3
1
2
3
3300
3300 3041.1
2736.1
2702.1
2613.4
2800 2349.2
2800
2394.7
2221.7
2300
2300
1958.5
1800 2037.7
1800
1923.5 2055.9
1659.6
1300 1132
1300
977
800
800
1
2
3
1
2
3
Infilled Bays
Infilled Bays
3023.0
2625.7
2900.8
Comparison of Frame and Panel Yield for all Frames and Infill
Configurations
NBCC Seismic Factor
Definition
Overstrength (Ro or Ω)
Ductility (Rd or µT)
• 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 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 Factors
9.0
8.0
7.8
6.9
7.0
D bare frame
D + 1 bay infill
D + 2 bay infill
D + 3 bay infill
LD bare frame
LD + 1 bay infill
LD + 2 bay infill
LD + 3 bay infill
Ductility
6.0
4.8
5.0
4.0
3.0
2.0
3.73.5 3.7
3.2
3.0
2.7
1.6
2.62.8
2.3
2.1 1.92.2
1.8
2.6
1.91.92.22.2
1.61.6
1.0
0.0
3
Ductility Factor for all Frames
6
Frame Storeys
9
NBCC Seismic Factors
D bare frame
D + 1 bay infill
D + 2 bay infill
D + 3 bay infill
3.5
3.0
Overstrength
2.5
2.0
2.0 2.0
1.5
1.0
2.2
2.0
2.0 2.0 2.0
1.81.9 1.8 1.8
1.7
LD bare frame
LD + 1 bay infill
LD + 2 bay infill
LD + 3 bay infill
2.3 2.3 2.3
2.1 2.1
2.02.0
1.8
1.2 1.1 1.1
1.3
0.5
0.0
3
6
Frame Storeys
Overstrength Factors for all Frames
9
Future Work
• FEMA P695 guidelines for dynamic analysis
• Partial Incremental dynamic analysis
– 22 ‘Far-Field’ ground motions
Acknowledgements
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.