37
Denis Mitchell McGill University 2013 UBC - Tongji - CSRN Symposium Modern Solutions to Seismic Risk Mitigation: A Sino-Canada Joint Effort Evaluation and Retrofit of Existing Shear Walls
Denis Mitchell
McGill University
2013 UBC - Tongji - CSRN Symposium
Modern Solutions to Seismic Risk Mitigation:
A Sino-Canada Joint Effort
Evaluation and Retrofit of
Existing Shear Walls
Poorly Detailed Walls (Kobe 1995)
• Thin wall
• No confinement
• Small amount
of uniformly
distributed
reinforcement
• Shear failure
D. Mitchell, McGill University
Mitchell, D., DeVall, R.H., Kobayashi, K., Tinawi, R. and Tso, W.K., “Damage to Concrete
Structures due to the January 17, 1995 Hyogo-Ken Nanbu (Kobe) Earthquake”, CJCE,
V23, N3, 1996.
Deficiencies in Existing Shear Walls
Lap Splice
Inadequate length
Critical location
Shear Reinforcement
Inadequate
Poorly anchored
Confinement
Thin Walls
Inadequate
confinement at ends
4
Test
Setup
350 mm
10M
lap splice
Reversed
cyclic
loading
150 mm
600 mm
20M lap
splice
10M @
250mm
As-Built Walls
Inadequate length of
lap splices
20M → 600 mm
10M→ 350 mm
Lap splices located in
the potential plastic
hinge region
2 - 20M
10M @ 277 mm
10M @ 250 mm
150 mm
1200
mm
45 mm 85 mm
150 mmW1 W2
4 - 20M
As-Built Walls
Flexural Reinforcement
W1: 2 – 20M
W2: 4 – 20M
Distributed Reinforcement
Vertical: (0.0015Ag)
Horizontal: (0.0025Ag)
Poorly anchored shear
reinforcement
Responses of W1 and W2
7
Layssi,H, Cook,W.D. and Mitchell,D., "Seismic Response and CFRP Retrofit of Poorly
Detailed Shear Walls", ASCE J. of Composites for Construction, V. 16, N. 2, 2012.
Responses of W1 and W2
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Lateral Displacement (mm)
Ap
plie
d S
he
ar
(kN
)
Maximum Load
W1
-1.0 -0.5 0.0 0.5 1.0Drift (%)
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Ap
plie
d S
he
ar
(kN
)
Lateral Displacement (mm)
-1.0 -0.5 0.0 0.5 1.0Drift (%)
W2
Maximum Load
Remarks
Brittle and premature tensile failure of lap splices
Low Energy dissipation
CFRP Retrofit
Full CFRP wrap
1800 mm
CFRP strips
100 mm @ 250 mm
100 mm
1800 mm
250 mm
CFRP
Direction of
fibers
150 mm
Responses of WRT1 & WRT2
-30 -20 -10 0 10 20 30
-150
-100
-50
0
50
100
150
Ap
plie
d S
he
ar
(kN
)
Lateral Displacement (mm)
Maximum LoadGeneral yield
WRT1
-1.0 -0.5 0.0 0.5 1.0Drift (%)
-45 -30 -15 0 15 30 45
-250
-200
-150
-100
-50
0
50
100
150
200
250
Ap
plie
d S
he
ar
(kN
)
Lateral Displacement (mm)
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
Drift (%)
Maximum LoadGeneral yield
WRT2
Yielding of flexural reinforcement (Ductility of 2.0)
Gradual deterioration of bond in the lap splice region
FRSCC Retrofit
FRSCC Jacket
Additional reinforcement
over the lap splice region
Full CFRP wrap
Beyond the Jacket
CFRP strips
Shear strengthening
FRSCC
jacket
100 mm
1175 mm
250 mm
CFRP
625 mm
350 mm
150 mm
Reversed
cyclic
loading
150 mm
12
Crushed concrete
Removed
Additional Reinf.
Flexural
Shear
Additional Concrete
SCC + steel fibres
Threaded rods shear
connectors
10M @
80 mm
1200
mm
66 mm
356 mm
356 mm
4 - 15M
350 mm
105 mm
100 mm
350 mm
2 - 15M
FRSCC Retrofit/Repair
13
FRSCC Retrofit
FRSCC Jacket
Additional reinforcement
over the lap splice region
Full CFRP wrap
Beyond the Jacket
CFRP strips
Shear strengthening
FRSCC
jacket
100 mm
1175 mm
250 mm
CFRP
625 mm
350 mm
150 mm
Reversed
cyclic
loading
150 mm
14
FRSCC Retrofit/Repair
Responses of WRP1 & WRP2
-60 -45 -30 -15 0 15 30 45 60
-200
-150
-100
-50
0
50
100
150
200
WRP1
Ap
plie
d S
he
ar
(kN
)
Lateral Displacement (mm)
Maximum LoadGeneral yield
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Lateral Displacement (mm)
Ap
plie
d S
he
ar
(kN
)WRP2
Maximum LoadGeneral yield
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
16
Remarks
Ductile response (Ductilities of 3.3 and 2.8)
Higher levels of dissipated energy
Prototype Structure
5 Storey Building
Storey Height: 12’
Shear Wall-Frame
Deficient Shear Walls
Frame with limited
ductility
Location
Montreal, QC
Vancouver, BC
17
Layssi,H, Seismic Retrofit of Deficient Reinforced Concrete Shear Walls, PHD
Thesis, McGill University, 2013
Uniform Hazard Spectra
Montreal Vancouver
18
0.0 1.0 2.0 3.0 4.0
0.0
0.2
0.4
0.6
0.8
1.0
Sp
ectr
al a
ccele
ratio
n (
g)
Period (sec)
Mont: 2%/50 years
Mont: 10%/50 years
0.0 1.0 2.0 3.0 4.0
0.0
0.2
0.4
0.6
0.8
1.0
Sp
ectr
al a
ccele
ratio
n (
g)
Period (sec)
Van: 2%/50 years
Van: 10%/50 years
NBCC 2005
Fibre Model vs. Test
W1 W2
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre modelA
pplie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
Fibre Model vs. Test
WRT1 WRT2-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre modelA
pplie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
Fibre Model vs. Test
21
WRP1 WRP2
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-30 -15 0 15 30
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)-30 -15 0 15 30
-250
-200
-150
-100
-50
0
50
100
150
200
250
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-150
-100
-50
0
50
100
150
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-60 -45 -30 -15 0 15 30 45 60
-300
-200
-100
0
100
200
300
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-200
-150
-100
-50
0
50
100
150
200
Test
Fibre model
Applie
d S
hear
(kN
)
Tip deflection (mm)
-75 -60 -45 -30 -15 0 15 30 45 60 75
-300
-250
-200
-150
-100
-50
0
50
100
150
200
250
300
Test
Fibre model
Tip deflection (mm)
Applie
d S
hear
(kN
)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-1.0 -0.5 0.0 0.5 1.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
Drift (%)
Results - non-linear static and
dynamic procedures
Montreal Vancouver
As-built NG NG
CFRP
retrofit
OK On limit
FRSCC
retrofit
OK OK
Poorly Detailed Walls (Chile 2010)
Wall
buckling90º bends
no confinement
Wall Details
• Wall thicknesses
varied from 175 to
250 mm
• Wall slenderness = 12
to 18
Chile wall details
400
4 – 22 mm bars
90º bends
Wall
Structure
Berkeley, CA
built in 1969
Mar,D., Panian,L., Dameron,R.A., Hansen,B.E., Vahdani,S., Mitchell,D. and Paterson,J.,
“Performance-Based Seismic Upgrade of a 14-Story Suspended Slab Building Using
State-of-the-Art Analysis and Construction Techniques”, SEAOC Convention, 2000.
Lap Splice
Retrofit
Paterson, J. and Mitchell, D., Seismic Retrofit of Shear Walls with Headed Bars
and Carbon Fiber Wrap”, J. Structural Engi. ASCE, Vol. 129, No. 5, 2003.
As-Built
Test
Paterson, J. and Mitchell, D., Seismic Retrofit of
Shear Walls with Headed Bars and Carbon
Fiber Wrap”, J. Structural Eng. ASCE, Vol.
129, No. 5, 2003.
Rd
1.5Standard 90-degree
hook around
vertical end bar
≤ 2.5
U-bar around
vertical end bars;
staggered lap
splices min. 5t from
end of wall
≤ 4.0 Anchored within
tied vertical
reinforcement
Anchorage of Horizontal Reinforcement
CSA A23.3-14, Design of Concrete Structures, Canadian Standards Association,
Mississauga, ON, 2014
Shear Walls
Shear failure,
Kobe
Poor
confinement,
Chile
Wall
buckling,
ChileD. Mitchell, McGill University
Shear
Walls
h 0.0020
v 0.0015
max 500 mms
3 b
0.0025
0.0025
500 mm
3max
s
h
v
b
450 mm
0.0025
0.0025
smax
h
v
Ties s 16dbl
48 dbh
b
Hoops
bh24d
b
6s dbl
/2
smax
300 mm (plastic hinge)
(a) (b) (c)
b b b
= 1.5Rd = 2.0Rd dR = 3.5
1 layer of steel if 210 mmb
2-15M minimum
bh(24 plastic hinge)d
b
(6 plastic hinge)dbl
/2( plastic hinge)
lw
lw
1.5
D. Mitchell, McGill University
