state-of-the-art studies on the behavior of coupling beams · state-of-the-art studies on the...
TRANSCRIPT
Zuozhou ZHAO
Department of Civil Engineering
Tsinghua University
State-of-the-art Studies on the Behavior of
Coupling Beams
June 28, 2019
2019/6/28
• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
Coupled shear walls(CSW) are widely used for tall reinforced
concrete (RC) buildings.
Overturning moment is resisted jointly by the bending action of the
wall units and the couple formed from axial forces developed in the
wall units by coupling beams(CBs).
Background
2019/6/28 3
Seismic design philosophy of CSWs
Strong coupling beams (CBs): shear walls may fail at their bases
first. This could endanger the safety of the building and render the
repair after earthquake very difficult.
Weak coupling beams (CBs): coupling beams will yield before the
walls yield. thereby protecting the walls from being damaged. Since
the coupling beams are easier to repair than the walls, most
earthquake resistant designs follow the strong wall-weak beam
philosophy.
Ideal failure sequence: Strong walls weak beams. Walls are the last
to yield so as to maintain lateral stability of the structure and allow
large deformation before collapse.
Coupling beams (CBs) are required being “fuse” and possessing
high rotation ductility. It is questionable whether deep RCCBs could
possess such a great rotation ductility.
Background
2019/6/28 4
5
Chile Earthquake
(2010)
Wenchuan Earthquake(2008)
Kobe Earthquake
(1995)
Loma Prieta Earthquake
(1989)
Damage of deep RCCBs after strong EQ
2019/6/28
Background
Coupling beam
Questions:
What is the behavior of a RC coupling beam (RCCB)?
How shear force is resisted by a deep RCCB?
How to improve the seismic behavior of a deep RCCB?
2019/6/28 6
• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
8
Strut-tie model Distributed truss model
Generalized truss model
分布桁架模型压杆模型
广义桁架模型
Shear force transfer mechanisms in a RCCB
Deep RC coupling beams (RCCBs) (l/h≤2.5)
Distributed truss model
Strut-tie model
Combination of the upper two models
Slender RC coupling beams (l/h>2.5)
Generalized truss model
2019/6/28
RC coupling beams(RCCBs)
9
Diagonally reinforced bars
Conventionally reinforced
Typical reinforced method of RCCBs
2019/6/28
RC coupling beams(RCCBs)
10 2019/6/28
Experimental study on deep RCCBs in HKU (Kwan and Zhao , 2002).
RC coupling beams(RCCBs)
Parameters of the specimens
11 Typical failure mode of Deep RCCBs
MCB4(flexural) MCB3(flexural) MCB1(shear tension) MCB2(flexural)
Shear tension Shear sliding failure Flexural shear
2019/6/28
RC coupling beams(RCCBs)
12
Typical failure mode of Deep RCCBs
CCB4
(flexural)
CCB12
(shear-sliding)
CCB1
(shear tension)
CCB11
(diag-bars buckling) 2019/6/28
Peak load
Failure
13 2019/6/28
-400
-300
-200
-100
0
100
200
300
400
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(kN
)
LVD T
(+)Lo ad
-150
-100
-50
0
50
100
150
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(kN
)
LVD T
(+)Lo ad
-400
-300
-200
-100
0
100
200
300
400
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(kN
)
LVD T
(+)Lo ad
-400
-300
-200
-100
0
100
200
300
400
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(K
N)
LVD T
(+)Lo ad
-150
-100
-50
0
50
100
150
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(kN
)
LVD T
(+)Lo ad
-400
-300
-200
-100
0
100
200
300
400
-50 -40 -30 -20 -10 0 10 20 30 40 50
Displacement (mm)
Lo
ad
(K
N)
LVD T
(+)Lo ad
CCB1 CCB4
CCB11 CCB12
Load-displacement curves of the conventionally RCCBs exhibit
substantial pinching, the curve of the diagonally reinforced RCCB
exhibits no pinching and appears to be more stable.
RC coupling beams(RCCBs)
14
Envelopes of the cyclic load-displacement curves
Envelopes of the cyclic load-displacement curves prove that as the
span/depth ratio of such conventionally reinforced RCCB decreased,
the load resisting capacity increased but the ductility decreased. CCB1
series have different reinforcement layouts but had similar load
resisting capacities and similar ductility.
2019/6/28
RC coupling beams(RCCBs)
15
Test results of the specimens under monotonic load and reversed cyclic load
Specime
n
h
(mm) L/h
fc’
(MPa)
rs
(%) rsv (%)
Applied load V (kN) Deflection D (mm) mD (=
Du/Dy) Failure mode
Vsh Vy Vp Vu Dsh Dy Dp Du
MCB1 600 1.17
45.5 0.485 1.069 264 262 344 292 11.52 10.50 42.50 60.00 5.7 shear-tension
CCB1 42.3 0.485 1.069 257 260 327 278 10.96 10.00 20.00 40.00 4.0 shear-tension
MCB2 500 1.40
45.7 0.486 1.069 237 198 260 221 11.92 5.97 41.04 69.00 11.6 flexural
CCB2 39.5 0.486 1.069 184 190 227 193 5.85 6.00 12.00 30.00 5.0 shear-compression
MCB3 400 1.75
35.0 0.496 1.069 156 126 159 135 37.00 4.00 38.00 49.00 12.3 flexural
CCB3 38.9 0.616 1.069 154 135 165 140 10.00 5.00 10.00 25.00 5.0 shear-sliding
MCB4 350 2.00
37.4 0.563 1.069 133 100 140 119 46.60 4.16 48.20 70.00 16.8 flexural
CCB4 37.7 0.563 1.069 114 110 123 104 12.00 6.00 12.00 36.00 6.0 flexural
2019/6/28
RC coupling beams(RCCBs)
16
0.000
0.004
0.008
0.012
0.016
-700 -350 0 350 700
Distance of cross section from centre of beam (mm)
Ro
tatio
n (
rad
ian
)
m =1
m =2
m =3
0.000
0.004
0.008
0.012
0.016
-700 -350 0 350 700
Distance of cross section from centre of beam (mm)
Ro
tatio
n (
rad
ian
)
m =3
m =1
m =2
0.000
0.004
0.008
0.012
0.016
-700 -350 0 350 700
Distance of cross section from centre of beam (mm)
Ro
tatio
n (
rad
ian
)
m =1
m =2
m =3
0.000
0.004
0.008
0.012
0.016
-700 -350 0 350 700
Distance of cross section from centre of beam (mm)
Ro
tatio
n (
rad
ian
)
m =1
m =2
m =3
CCB1 CCB4
CCB11 CCB12
Large local rotations took place at the beam-wall joints when the main
or diagonal bars yielded. The additional displacements arising from the
local rotations of the beam-wall joints contributed about 35 to 70 % to
the total lateral displacements when m=3.
2019/6/28
RC coupling beams(RCCBs)
17
Axial elongation of a deep RCCB
2019/6/28
-400
-300
-200
-100
0
100
200
300
400
0 0.005 0.01 0.015 0.02 0.025
Average elongation strain (mm/mm)
Lo
ad
(kN
)
-150
-100
-50
0
50
100
150
0 0.005 0.01 0.015 0.02 0.025
Average elongation strain (mm/mm)
Lo
ad
(kN
)
-400
-300
-200
-100
0
100
200
300
400
0 0.005 0.01 0.015 0.02 0.025
Average elongation strain (mm/mm)
Lo
ad
(kN
)
-400
-300
-200
-100
0
100
200
300
400
0 0.005 0.01 0.015 0.02 0.025
Average elongation strain (mm/mm)
Lo
ad
(kN
)
CCB1 CCB4
CCB11 CCB12
Axial elongation increased quickly after yield load. The maximum
average elongation strains recorded for the conventionally
reinforced coupling beams were around 1.2 to 2.0% and that for the
diagonally reinforced coupling beam was about 2.5 %.
18
Behavior of deep RCCBs
Behavior of the deep RCCBs in shear wall system is different from
frame beams in several aspects:
The stress distribution in the flexural reinforcement in a coupling
beam is consistent with the moment distribution before the
appearance of shear crack, just like a frame beam. After shear
cracking, both the top and the bottom reinforcing bars are subject
to tension within most of the span, as a result, the contribution of
the compression reinforcement to load resisting capacity and
ductility will not exist and lead to specially failure modes .
The local deformation at the beam-wall joint is much larger than
deformation of the beam itself.
Besides local failure such as anchorage failure and bearing failure,
the failure modes of coupling beams can be classified as flexural or
flexural shear failure, shear tension (diagonal splitting) failure and
shear sliding failure respectively.
2019/6/28
19
Full slit (Li and Li, 1984)
slit
Different reinforced concrete coupling beams
Multi-slit (Cheng et al., 1993)
short slit
concrete key
Partial slit (Ding et al., 1997)
a hole
keyway
Reinforcement layout in slit coupling beam
2019/6/28
Behavior of deep RCCBs
• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
21
Steel plate reinforced RC coupling beams (RCCBs) is an alternative
way of RC coupling beams. Steel plate in a RC deep coupling beam
can easily improve the shear resisting capacity of the RC coupling
beams.
Steel plate reinforced RC coupling beam
Shear Stud
Steel Plate
WallWall
Section A-A
Shear Stud
Steel Plate
Coupling Beam
Elevation
(Su and Lam, 2002)
2200
575 焊接钢筋
1250
150
附加钢筋
450
150
500
A——A
575
750
150
角钢
钢板
AA
Φ 8@100125
150
2Φ 16 2Φ 164Φ 12
300
2Φ 12
(Zhao and Zhang, 2005) 2019/6/28
22
Steel plate reinforced RC coupling beam
(Su and Lam 2002)
Load-Rotation Envelopes
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08
q (Rad)
V (
kN
)
Unit 1
Unit 2
Unit 3
Load-Rotation Curve - Unit B3
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08
q (Rad)
V (
kN
)
V u *
m
0 10 128 146 1642-10 -2-4-16 -6-12 -8-14
7R8 - 100
2T20 - t&b
B3
B3
Section B3-B3
Load-Rotation Curve - Unit B4
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08
q (Rad)
V (
kN
)
V u *
m
0 84 102-2-10 -4-8 -6 6
7R8 - 100
2T20 - t&b
Grade 50 Plate10mm thk x 240mm dp
B4
B4
Section B4-B4
Load-Rotation Curve - Unit B5
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08
q (Rad)
V (
kN
)
m
0 8642-2-4-6-8
V u *
7R8 - 100
2T20 - t&b
Shear Studat 100 c/c
B5
B5
Section B5-B5
Grade 50 Plate10mm thk x 240mm dp
Su and Lam (2002) studied the feasibility of a new coupling beam
design making use of the composite action between an embedded
steel plate and its surrounding reinforced concrete via shear studs. It
was proven that the use of embedded steel plates could increase the
strength and stiffness of coupling beams while maintaining small
sectional sizes, but shear studs are necessary to ensure desirable
inelastic beam behaviours.
2019/6/28
23
Steel plate reinforced RC coupling beam
2200
575 焊接钢筋
1250
150
附加钢筋
450
150
500
A——A
575
750
150
角钢
钢板
AA
Φ 8@100
125
150
2Φ 16 2Φ 164Φ 12
300
2Φ 12
One steel plate was embedded and extended into wall blocks at both
ends. A steel angle was welded at each end of the steel plate to
ensure its anchorage in the wall blocks.
Two deformed bars were welded on each side of the plate.
2200
575 焊接钢筋
1250
150
附加钢筋
450
150
500
A——A
575
750
150
角钢
钢板
AA
Φ 8@100
125
150
2Φ 16 2Φ 164Φ 12
300
2Φ 12
2019/6/28
specimen
24
Steel plate reinforced RC coupling beam
Six coupling beams were tested. The thickness and clear span of the
specimens were fixed at 150 mm and 750 mm respectively.
Variables: span/depth ratio; steel plate section; steel ratio
Details of the specimens
2019/6/28
25
Steel plate reinforced RC coupling beam
D8
D6
D7
D3
D4
D5
D2
D1
Displacements were measured using linear variable displacement
transducers (LVDTs).
Strains of longitudinal bas, stirrups and steel plates were obtain by
using strain gauges.
Deflection monitoring Strain monitoring 2019/6/28
26
Steel plate reinforced RC coupling beam
The test setup was the same as RCCBs test. The specimen was
erected with beam longitudinal axis in the vertical direction. Shear
load was applied to the specimen through the L-shaped loading frame.
The action line of the applied load passed through the mid-span of the
beam specimen. A rotation restraint mechanism was installed.
Test setup
Reaction Wall
L-Shaped
Loading Frame
Specimen
Base Beam
600 kNActuator
Balance
Weight
Balance
Weight
Rotation Restraint
Mechanism
2019/6/28
27
CB15-1 CB15-2 CB15-3 CB15-4
Steel plate reinforced RC coupling beam
Peak load
Failure
2019/6/28 Crack pattern and failure modes
28
CB25-1 CB25-2
Steel plate reinforced RC coupling beam
Failure Peak load Failure Peak load
2019/6/28
Crack pattern and failure modes
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
荷载
(kN
)
(+
D3
D5
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
29
Steel plate reinforced RC coupling beam
CB15-2 CB15-3
CB15-4 CCB2
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
CB15-1
Compare the hysteretic curves of CB15 series with that of CCB2, the
introduction of steel plate in a coupling beam can not only increase the
strength and energy dissipation capacity, but increase the stiffness of the
beam under reversed cycle loading and greatly reduce the pinching effect of
the load-rotation curve.
2019/6/28
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
30
Steel plate reinforced RC coupling beam
Unit 3-Lam(2005)
CB25-1
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
θ=(D3-D5)/d (rad)
loa
d (
kN
)
(+
D3
D5
CB25-2
Unit 1-Lam(2005)
For CB25 series and Lam’s specimens, there is similar phenomenon.
2019/6/28
31
Steel plate reinforced RC coupling beam
CB25 series & UNit3-Lam
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
转角 θ (rad)
荷载
(kN
)
CB15-1
CB15-2
CB15-4
CB15-3
CCB2-ZZZ
(a) CB15 骨架曲线
q
V
-500
-400
-300
-200
-100
0
100
200
300
400
500
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
转角 θ (rad)
荷载
(kN
)
Lam-CF
CB25-2CB25-1
(b) CB25 骨架曲线
q
V
CB15 series & CCB2-ZZZ(l/h=1.4)
Compare the skeleton curves of CB15 series with that of CCB2-ZZZ(l/h=1.4)
and CB25 series and UNit3-Lam, the introduction of steel plate in a coupling
beam can not only increase the strength and energy dissipation capacity, but
increase the stiffness of the beam under reversed cycle loading and greatly
reduce the pinching effect of the load-rotation curve.
2019/6/28
32
Steel plate reinforced RC coupling beam
Specimen Vy
(kN)
Vu
(kN)
Ratation (10-3rad) Ductility ratio Failure mode
θy(rad) θu(rad) Θu1(rad) θu/θy θu1/θy
CB15-1 241 377 3.66 25.00 44.52 6.83 12.16 Flexural Shear
CB15-2 252 363 3.88 18.12 25.96 4.67 6.69 Flexural Shear
CB15-3 292 367 5.43 11.94 26.44 2.20 4.86 Flexural
CB15-4 223 340 3.76 12.25 31.38 3.26 8.35 Flexural Shear
CB25-1 156 198 7.71 16.23 26.81 2.10 3.48 Shear
CB25-2 191 254 6.56 14.91 29.54 2.27 4.50 Flexural Shear
Load and deflection characteristic parameters of the specimens
CB15-3 and CB15-4 have the highest and lowest yield strength
respectively, which may result from the depth of the steel plate
encased in the specimen.
CB15-1 and CB15-2 have similar steel plate reinforcement ratio and
hence have similar load capacity.
CB15-4 have a large steel plate while has the lowest load capacity
due to anchorage failure of steel plate in the wall piers. So enough
anchorage of steel plate must be provided.
2019/6/28
33
Steel plate reinforced RC coupling beam
Specimen Vy
(kN)
Vu
(kN)
Ratation (10-3rad) Ductility ratio Failure mode
θy(rad) θu(rad) Θu1(rad) θu/θy θu1/θy
CB15-1 241 377 3.66 25.00 44.52 6.83 12.16 Flexural Shear
CB15-2 252 363 3.88 18.12 25.96 4.67 6.69 Flexural Shear
CB15-3 292 367 5.43 11.94 26.44 2.20 4.86 Flexural
CB15-4 223 340 3.76 12.25 31.38 3.26 8.35 Flexural Shear
CB25-1 156 198 7.71 16.23 26.81 2.10 3.48 Shear
CB25-2 191 254 6.56 14.91 29.54 2.27 4.50 Flexural Shear
Load and deflection characteristic parameters of the specimens
CB25-2 has a thicker steel plate, so its load resisting capacity and
energy dissipation capacity are much higher than that of specimen
CB25-1. Its yield load and peak load is increased by more than 20%.
During post peak stage, yielding of the longitudinal bars and
stirrups led to decreasing of load resisting capacity.
Specimen with large plate section area has a stable load-deflection
hysteretic curve. This proves that the minimum steel plate
reinforcement ratio should be met to obtain desired performance.
2019/6/28
34
Steel plate reinforced RC coupling beam
Shear resisting capacity of the steel plate reinforced RCCB affected by
steel plate reinforcement ratio, depth, thickness, depth/thickness ratio,
using FE method.
Depth Depth/Thickness Ratio
0
2
4
6
8
10
12
14
16
0 1 2 3 4
V/b
h0 (
Mp
a)
Plate Reinforcement Ratio (%)
0
2
4
6
8
10
12
14
16
0 2 4 6 8
D=180mm
D=420mm
V/b
h0 (
Mp
a)
Thickness (mm)
0
2
4
6
8
10
12
14
16
0 100 200 300 400 500
t=3mm
t=6mm
V/b
h0 (
Mp
a)
Depth (mm)
0
2
4
6
8
10
12
14
16
0 50 100 150
ρ=0.01787
ρ=0.03574
V/b
h0 (
Mp
a)
Depth/Thickness
Plate Reinforcement Ratio Plate Thickness
2019/6/28
• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
36
Advantage of Precast structures (PC VS Cast-in-site RC):
Higher construction quality
Possible increased construction speed
Improved durability
Reduction in situ labor or waste
Seismic design are required for precast structures.
Precast residential buildings in China are mostly designed as
precast shear wall structures. Precast wall systems can be
classified into two types:
Jointed system: “dry” or “ductile” connections (damages
concentrate on connections)
Equivalent monolithic system: “wet” or “strong” (same as
cast-in-situ structures)
Assembled RC coupling beam
2019/6/28
37
Assembled RC coupling beam
The assembled RC coupling beam includes the top and the bottom
precast RC segment combined together by the center cast-in-place
RC slab boundary.
Seismic behavior of the assembled RC coupling beam under
simulated cyclic loading have been studied carefully and some
detailing methods have been proposed. Some studies conducted
in Tsinghua University are briefly introduced. (Qian and Zhao,2013)
2019/6/28
assembled RC coupling beam
38
Assembled RC coupling beam
2019/6/28
Group Specimen L
(mm)
h
(mm) L/h
Connection method with
the upper part
A A 2400 1300 1.85 Grouted couplers
B B 2400 1300 1.85 None
C
C1 1500 1000 1.5 Grouted couplers
C2 2000 1000 2.0 Grouted couplers
C3 2400 1000 2.4 Grouted couplers
D
D1 1500 1000 1.5 None
D2 2000 1000 2.0 None
D3 2400 1000 2.4 None
E E 1500 500 3.0 -
Test of 9 assembled RCCB specimens with different connection
methods between the upper and the lower part has been carried out
in Tsinghua Univerty.
Details of the specimens
39
Assembled RC coupling beam
2019/6/28
250
8080
530
A
A
C
B
DE
A
序号 配筋 序号 配筋
C
E
B
D
8 16 4 162 1612@100
12@100
250
200
400
200
A
6
7
10
11
9
8
13
12
1
2
345
9
A
200
250
250
200
400
200
B
A
C
B
DE
端部搭接焊接,焊缝长度不小于50mm(其余相同)
530
180
AB
不小于50mm(单面焊)
250250
400
400
1380
830
200
200
不小于80mm(单面焊)
1
2
7
891011
12
3456
13
14
A
12d
13
6B
9
200
250
250
400
400
10
7
9
6
11
8
1
2
345
8
6B
250
250
200
500
C
7
6
8
9
1
2
345
250
250
200
500
D A B
1
2
345
250
250
200
E
Connection detailing of the assembled RCCB specimens.
40
Assembled RC coupling beam
2019/6/28
Crack pattern of the assembled RCCBs (Qian and Zhao, 2013)
A B C1 C2 E
41
Assembled RC coupling beam
-150 -100 -50 0 50 100 150-600
-400
-200
0
200
400
600
q
F/K
N
/mm
-0.06 -0.04 -0.02 0.00 0.02 0.04 0.06
2019/6/28
A
-150 -100 -50 0 50 100 150-600
-400
-200
0
200
400
600
q
F/K
N
/mm
-0.06 -0.04 -0.02 0.00 0.02 0.04 0.06
B
-150 -100 -50 0 50 100 150-600
-400
-200
0
200
400
600
q
F/K
N
/mm
-0.09 -0.06 -0.03 0.00 0.03 0.06 0.09
C1
-150 -100 -50 0 50 100 150
-600
-400
-200
0
200
400
600
q
F/K
N
/mm
-0.09 -0.06 -0.03 0.00 0.03 0.06 0.09
D1
-150 -100 -50 0 50 100 150-600
-400
-200
0
200
400
600
q
F/K
N
/mm
-0.09 -0.06 -0.03 0.00 0.03 0.06 0.09
E
42
Assembled RC coupling beam
2019/6/28
Measured and predicted capacity of assembled RCCBs
Specimen Model
Predicted Measured Fp(kN) Measured/Predicted
Vu
(kN)
2Mu/L
(kN) Positive Negative Average
Fp/ Vu Fp/(2Mu/L)
A 1 beam 584 300
571 455 513 0.89 1.71
2.82 2 beam 639 182 0.80
B 1 beam 584 294
468 375 422 0.72 1.44
1.88 2 beam 646 224 0.65
C1 1 beam 491 359
500 451 475 0.97 1.32
2.49 2 beam 543 191 0.87
C2 1 beam 496 269
446 376 411 0.83 1.53
2.87 2 beam 548 143 0.75
C3 1 beam 494 224
381 330 356 0.72 1.59
2.99 2 beam 545 119 0.65
D1 1 beam 574 361
653 504 578 1.00 1.60
2.13 2 beam 636 271 0.91
D2 1 beam 604 271
352 357 354 0.59 1.31
1.74 2 beam 669 204 0.53
D3 1 beam 573 226
302 293 298 0.52 1.32
1.75 2 beam 631 170 0.47
E — 348 109 204 175 189 0.54 1.73
43
3-story full-scale PC shear wall structure model
Global experimental study on a 3-story full-scale precast concrete shear wall structure with rebars spliced by grouted couplers in Tsinghua University.
2019/6/28
11
00
12
00
70
07
00
15
00
80
03
00
03
00
06
00
0
700 1200 1100
90
01
20
09
00
90
01
20
09
00
200
20
0
200
650 1500 650
18
0
900 1200 9003000
20
0
1 2
A
B
C
44
3-story full-scale PC shear wall structure model
Foundation beamAxes A
Axes B
Axes C
Axes 2
Axes 1
1F
3F
2F
3.0 m 3.0 m
3.0 m
3.0
m3.0
m3.1
m
WestEast
Loading beam
PCSW
Sealant-filled gap
Grout-filled gap
Polystyrene block
Window belly wall
Coupling beam
Precast wall or inner wythe of PCSWPolyurethane insulation layer of PCSW
Outer wythe of PCSW
Vertical post-casting segment
Horizontal post-casting segment
Precast bottom slab of composite slab
Cast-in-situ topping of composite slab
Slab-to-slab joint of composite slab
1
2
3
4
6
5
Boundary vertical rebar
20 mm thick grout-filled gap
TGC
Lower precast wall
Single-row additional rebar
Web distributed rebar
20 mm thick grout-filled gap
TGC
Noncontact lap
Lower precast wall
Upper precast wall
Boundary element Wall web
1 Horizontal wall-to-wall joint
200
22d400
All horizontal rebars spliced with 90° standard hooks
U-shaped rebar
200
20d400
24d
26d
Welded closed stirrup
Precast panel
Rectangular segment L-shaped segment
2 Vertical wall-to-wall joint
1200
1000
340 1
40
20
Window belly wall precast with wall limbs as a whole
D6@2002D12
Polystyrene block
100
200
500
300
Wall rebar
Coupling beam20 mm thick grout-filled gap and no rebar spliced
3 Detail of window belly wall (located on axes A and 2)
Cast-in-place topping
Precast bottom slab
Bottom slab rebar
230
50
70
Additional rebar 4D10
120
5 Slab-to-slab joint of composite concrete slabRebar truss
D8@200
Precast bottom slabBottom slab rebarD8@200
Cast-in-situ topping
50
70
120
Precast wall
Additional RebarD8@200
Precast wall
Precast bottom slabBottom slab rebarD8@200
50 1
20
37dD8@200
RPS (1F and 3F)
NRPS (2F)6 Slab-to-wall joint
4 Detail of PCSW (located on axes C and 2)
200500 500
200 70 60
20 mm thick sealant-filled gap
Concrete outer wythePolyurethane insulation layerInner wythe (Structural wall)
FRP connector spaced at 500 mm
Foundation beamAxes A
Axes B
Axes C
Axes 2
Axes 1
1F
3F
2F
3.0 m 3.0 m
3.0 m
3.0
m3.0
m3.1
m
WestEast
Loading beam
PCSW
Sealant-filled gap
Grout-filled gap
Polystyrene block
Window belly wall
Coupling beam
Precast wall or inner wythe of PCSWPolyurethane insulation layer of PCSW
Outer wythe of PCSW
Vertical post-casting segment
Horizontal post-casting segment
Precast bottom slab of composite slab
Cast-in-situ topping of composite slab
Slab-to-slab joint of composite slab
1
2
3
4
6
5
Boundary vertical rebar
20 mm thick grout-filled gap
TGC
Lower precast wall
Single-row additional rebar
Web distributed rebar
20 mm thick grout-filled gap
TGC
Noncontact lap
Lower precast wall
Upper precast wall
Boundary element Wall web
1 Horizontal wall-to-wall joint
20
0
22d400
All horizontal rebars spliced with 90° standard hooks
U-shaped rebar
20
0
20d400
24d
26
d
Welded closed stirrup
Precast panel
Rectangular segment L-shaped segment
2 Vertical wall-to-wall joint
1200
10
00
34
0 14
02
0
Window belly wall precast with wall limbs as a whole
D6@2002D12
Polystyrene block
100
20
05
00
30
0
Wall rebar
Coupling beam20 mm thick grout-filled gap and no rebar spliced
3 Detail of window belly wall (located on axes A and 2)
Cast-in-place topping
Precast bottom slab
Bottom slab rebar
230
50
70
Additional rebar 4D10
12
0
5 Slab-to-slab joint of composite concrete slabRebar truss
D8@200
Precast bottom slabBottom slab rebarD8@200
Cast-in-situ topping
50
70
12
0
Precast wall
Additional RebarD8@200
Precast wall
Precast bottom slabBottom slab rebarD8@200
50 1
20
37dD8@200
RPS (1F and 3F)
NRPS (2F)6 Slab-to-wall joint
4 Detail of PCSW (located on axes C and 2)
200500 500
200 70 60
20 mm thick sealant-filled gap
Concrete outer wythePolyurethane insulation layerInner wythe (Structural wall)
FRP connector spaced at 500 mm
2019/6/28
Detailing of the assembled RC coupling beams: upper belly wall (non
structure element) + grout-filled gap + bottom coupling beam. All
window belly walls and the lower segments were connected by a 20
mm thick high-strength grout-filled construction gap, no rebar spliced.
45
3-story full-scale PC shear wall structure model
The 3-story full-scale precast concrete shear wall structure model.
Actuators
Loading beam
Reaction floor
Anchoring end
E
W N
S
Tensioning end
Reaction wall
Foundation beamFixed beam
Prestressing tendons
Displacement transducer
2019/6/28
46
3-story full-scale PC shear wall structure model
0.035g
0.07g 0.20g 0.40g
0.62g
PsD test QuS test
LST
LST LST LST LST
LST: lateral stiffness test with a top lateral displacement amplitude of 2 mm.
Top displacement or PGA
1/500
1/300
1/200
1/120
1/100
1/75
1/60
1/50
Loading protocol
2019/6/28
3-story full-scale PC shear wall structure model
(a) 0.07g PGA (b) 0.20g PGA (c) 0.40g PGA
(d) 0.62g PGA (e) PsD and QuS tests (f) story drift
-400
-300
-200
-100
0
100
200
300
400
-3.0 -2.0 -1.0 0.0 1.0 2.0 3.00
u (mm)-3 -1 2
FE
K (
kN
)
-400
-300
0
100
200
3
-200
-100
300
400
-2 1
0θ (%)
-0.03 -0.01 0.02 0.03-0.02 0.01
FEK,max(kN) θmax
305.5 1/4114
279.5 1/4298
(+)
(-)
-800
-600
-400
-200
0
200
400
600
800
-9.0 -6.0 -3.0 0.0 3.0 6.0 9.00
u (mm)-9 -3 6
FE
K (
kN
)-800
-600
200
400
9
-400
-200
600
800
-6 3
0θ (%)
-0.09 -0.03 0.06 0.09-0.06 0.03
FEK,max(kN) θmax
772.7 1/1041
737.7 1/1010
(+)
(-)
-1600
-1200
-800
-400
0
400
800
1200
1600
-30.0 -20.0 -10.0 0.0 10.0 20.0 30.00
u (mm)-30 -10 20
FE
K (
kN
)
-1600
-1200
0
400
800
30
-800
-400
1200
1600
-20 10
0θ (%)
-0.3 -0.1 0.2 0.3-0.2 0.1
FEK,max(kN) θmax
1525.6 1/316
1447.9 1/309
(+)
(-)
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-60.0 -40.0 -20.0 0.0 20.0 40.0 60.0
FE
K (
kN
)
-2000
-1500
0
500
1000
-1000
-500
1500
20000θ (%)
-0.6 -0.2 0.4 0.6-0.4 0.2
0u (mm)
-60 -20 40 60-40 20
FEK,max(kN) θmax
2040.9 1/129
1895.7 1/169
(+)
(-)
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-200 -150 -100 -50 0 50 100 150 200
FE
K (
kN
)
-2000
-1500
0
500
1000
-1000
-500
1500
2000
0u (mm)
-200 -100 100 200
0θ (%)
-2 -1 1 2
Hysteretic loopSkeleton curve
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-75 -50 -25 0 25 50 75F
EK (
kN
)
-2000
-1500
0
500
1000
-1000
-500
1500
2000
0Story drfit (mm)
-75 -25 50 75-50 25
0Story drift ratio (%)
-2 -1 21
1st story2nd story3rd story
Hysteretic loops or skeleton curves under different load conditions
2019/6/28 47
South facade (axes A)
West East
East West
East West
West East
Wall on axes C of 1st story
Wall on axes B of 1st story
Wall on axes A of 1st story
1st story slab
2nd story slab
3rd story slab
Windowbellywall
Couplingbeam
Cracking
2.0
m
1.4
m
1.4
m
2.0
m
Failure modes of the test model after QuS test
After the 1st cycle of 1/50 drift,
the QuS test was terminated for
safety reasons.
Cracks and damages of the test
model concentered on the
coupling beams and window belly
walls in loading direction.
Cracks of walls distributed at a
height of 0 ~ 2.0 m from the
foundation, with a maximum
width of 2 mm.
No crack was observed at wall
limbs of the 2nd and 3rd story.
The test model exhibited the
desired “strong wall limb and
weak coupling beam” failure
mode.
2019/6/28 48
Failure modes of coupling beams and window belly walls
After 0.40g PsD test, all coupling beams were dominated by flexural
cracks, while shear cracks developed at the window belly walls
located on axes A and C at the 2nd and 3rd story.
After QuS test, the window belly walls on axes A and C failed in
shear mode. Influenced by the upper window belly walls, coupling
beams located on axes A and C at the 1st and 2nd story with aspect
ratios of 2.5 were dominated by shear inclined cracks.
Axes A
Window belly wall of 3rd storyCoupling beam of 2nd story
1200 mm
480 m
m420 m
m
After 0.40g PsD test
After QuS test
Coupling beam of 2nd story
Axes C 2019/6/28 49
1200 mm
58
0 m
m
1200 mm
58
0 m
mAxes A
Axes C
Coupling beams at the 3rd story, after QuS test
Note that coupling beams located on axes A and C at the 3rd story,
with aspect ratios of 2.1 and no upper window belly wall, failed in
flexural mode, characterized by concentrated plastic hinges at both
ends and slight shear cracks.
Failure modes of coupling beams and window belly walls
It can be concluded that upper window belly walls significantly
influenced the failure modes of coupling beams. A composite effect
existed in the lower coupling beam and upper window belly wall.
Designing the window belly wall as a upper coupling beam to form
double coupling beams may be a feasible alternative.
2019/6/28 50
51
3-story full-scale PC shear wall structure model
LB4 LB1
A new research program on assembled RCCBs, especially composite effect
between the window belly wall and the lower coupling beams are carried out
in Tsinghua University.
2019/6/28
• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
53
Wall
pier
Shear link
Wall
pier
Beam segment
Foundation
Replaceable steel coupling beam (RSCB)
Wall
pier
Shear link
Wall
pier
Beam segment
Foundation
Ground motion
FoundationFoundation Replacement
Wall
pier
Wall
pier
Beam segment(Damage)
Shear link
A type of replaceable steel coupling beam, with a central fuse shear
link connecting with normal steel beam segment at its two ends, has
been proposed and studied in Tsinghua Univ. (Ji and Wang 2016)
2019/6/28
54
3 Key issues should be considered.
Very short shear links
Link-to-beam connections
RC slab design
Shear link
Replacement
Wall
pier
Wall
pier
Beam segment
Replaceable steel coupling beam (RSCB)
2019/6/28
55
Wall
pier
Shear link
Wall
pier
Beam segment
e
l
Shear link Yield in shear
Beam
segment
Flexural strength
Link-to-beam
connection
e/(Mp/Vp)<1.6
Vp=0.6fyAw Yield strength
Mbp>0.5l·(ΩVp)
Vbp> Ω Vp Shear strength
Vcp> Ω Vp
Mcp>0.5e’·(Ω Vp) Flexural strength
Shear strength
Capacity design philosophy of RSCBs
2019/6/28
56
e/(Mp/Vp) < 1.0 e/(Mp/Vp) ≈ 1.5 Length
ratio
RSCBs EBFs
Shear links (per AISC 341 & GB 50011)
Wall
pier
Shear link
Wall
pier
Beam segment
e
2019/6/28
57
Vp
Vpn
Vp
Vpn
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2-1200
-800
-400
0
400
800
1200
Sh
ea
r fo
rce
V (
kN
)Inelastic rotation γp (rad)
0.08 rad required by AISC 341
Test of very short shear links
e/(Mp/Vp) = 0.87 Length ratio:
Hybrid section: LY 225/Q235 for link web and Q345 for flanges
2019/6/28
Overstrength Ω = Vmax/Vn
Length ratio e/(Mp/Vp)
Ove
rstr
en
gth
Vm
ax/V
n
0
0.5
1
1.5
2
2.5
0 1 2 3 4 5
Hjelmstad et al.Okazaki et al., 2007Malley et al.
Dusicka et al.
Ramadan et al.
Okazaki et al., 2009Kasai et al.
Engelhardt et al.
McDaniel et al.
Ricles et al.Mansour et al.This study
Bending Moment
Shear force
Plastic hinge
γ
V
γ
Secondary
tensile force
V
58
The very short shear links generated an overstrength factor
of approximately 1.9, significantly exceeding the value of 1.5
assumed for EBF links in the AISC 341-10 provisions. 2019/6/28
59
VM
Web splice plates resist all shear force
Flange splice plates resist all moment FM1
FM2
Fv
Splice plate
Shear key
VM
Bolts resist all moment
Shear key resists all shear force
FB
Fv
FBT
C
I-shaped section link
CB1: End plate connection
I-shaped section link
CB2: Splice plate connection
Test of link-to-beam connection
2019/6/28
60
Adhesive resists eccentric shear
VM
Adhesive
Instantaneous center
r
Bolts resist eccentric shear
VM
Epoxy adhesive fv = 15 MPa
Double channel section link
CB3: Bolted web connection
Double channel section link
CB4: Adhesive web connection
2019/6/28
61
Test setup
2019/6/28
62
Loading protocol B
ea
m r
ota
tio
n φ
(ra
d)
20-0.1
-0.05
0
0.05
0.1
0 5 10 15 25Cycles
0.005
0.01
0.5Vp
Vp0.02
0.03
0.04
0.05
0.06
0.07
0.015
0.08
Link replacement
Phase I 0.02 rad
Phase II Fail
Phase I: load to 0.02 rad rotation
Phase II: load till failure
Replacement of the shear link
2019/6/28
63
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
CB1 CB2
CB3 CB4
Phase I test
Vp
Vpn
Vp
Vpn
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
2019/6/28
64
CB1 CB2
CB3 CB4: Adhesive fracture
Phase I test
Vp
Vpn
Vp
Vpn
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
Beam
segment
Shear link
Adhesive
fracture
2019/6/28
65 CB1 CB2 CB3
Coupling beam
Vp
Vpn
Vp
Vpn
-0.09 -0.06 -0.03 0 0.03 0.06 0.09-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.09 -0.06 -0.03 0 0.03 0.06 0.09-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.09 -0.06 -0.03 0 0.03 0.06 0.09-1200
-800
-400
0
400
800
1200
Beam rotation φ (rad)
Sh
ea
r fo
rce
V (
kN
)
Shear link
Vp
Vpn
Vp
Vpn
-0.18 -0.12 -0.06 0 0.06 0.12 0.18-1200
-800
-400
0
400
800
1200
Link rotation ϒ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.18 -0.12 -0.06 0 0.06 0.12 0.18-1200
-800
-400
0
400
800
1200
Link rotation ϒ (rad)
Sh
ea
r fo
rce
V (
kN
)
Vp
Vpn
Vp
Vpn
-0.18 -0.12 -0.06 0 0.06 0.12 0.18-1200
-800
-400
0
400
800
1200
Link rotation ϒ (rad)S
he
ar
forc
e V
(kN
)
Phase II test
2019/6/28
66
Spec.
No.
Connection
type
Ultimate
rotation
(rad)
Residual
rotation for
replacement
(rad)
Replacement
time
(hour)
CB1 End plate
connection 0.06 0.0045 0.4
CB2 Splice plate
connection 0.09 0.0045 2.6
CB3 Bolted web
connection 0.06 0.0065 2.2
CB4 Adhesive web
connection 0.003 —— ——
Replaceability
(Ji and Wang 2016) 2019/6/28
67
CBS1: Composite slab
RC slab
Shear link
Headed Stud
Beam segment
Shear key
RC slab design
2019/6/28
68
CBS2: Isolated slab
CBS3: Bearing slab CBS4: Slotted slab
CBS1: Composite slab
polystyrene sheetBent rebar
Shear link
RC slab
Beam segment
Separation
(50 mm)
Shear link
RC slab
Beam segment
Shear link
RC slab
Beam segment
RC slab
Shear link
Headed Stud
Beam segment
Shear key
2019/6/28
69
RC slab
Beam segment
Shear link
2019/6/28
70
Studs pulled out
Slab damage
• At 0.04 rad beam rotation, most of shear studs pulled out
from the RC slab, and the rebars were exposed and buckled.
• Shear studs are NOT recommended for use between the
RSCBs and their above slabs.
Concrete cover
spalling
Exposed rebar
2019/6/28
71
polystyrene sheetBent rebar
Shear link
RC slab
Beam segment
CBS2: Isolated slab (GOOD)
CBS3: Bearing slab (FAIR) CBS4: Slotted slab (FAIR)
CBS1: Composite slab (BAD)
Separation
(50 mm)
Shear link
RC slab
Beam segment
Shear link
RC slab
Beam segment
RC slab
Shear link
Headed Stud
Beam segment
Shear key
2019/6/28
72
Beijing Sancai Building (11 story, 48.5 m)
2019/6/28 72
73
48600
8100 8100 8100 8100 8100 8100
6000
8400
14400
Longitudinal
Transverse
Hybrid coupled wall
RSCBs
RC coupling
beams
RC beamsRC slab RC columns
Design basis earthquake (DBE) PGA 0.2g
Period:1.57 s (Y)、1.53 s (X)、1.26 s (Torsion)
Seismic design: linear spectrum analysis under SLE
Interstory drift ratio (SLE) < 1/800
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• Background
• RC coupling beams
• Steel plate reinforced RC coupling beams
• Assembled RC coupling beams
• Replaceable steel coupling beams
• Conclusions
Outlines
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Conclusions Deep RCCBs behaved quite differently from ordinary frame beams after
the appearance of inclined shear cracks. All the longitudinal reinforcement
bars becoming in tension and the beams starting to elongate. The elongation
strains of the beams were of the order of 1.5 to 2.5 %.
High nominal shear stresses had led to the tendency of the deep RCCBs
to fail in shear. Additional displacement due to the local rotations at the
beam-wall joints had contributed about half to the total lateral displacement
and resulted in the above relatively high drift ratios. Diagonally reinforced
deep RCCB had a more stable hysteretic load-displacement curve and a
much better energy dissipation capacity. Sufficient lateral hoops should be
provided along the diagonal reinforcement.
Steel plate RCCB can improve the behavior of Deep RCCB. Steel plate
can resist more shear force with the displacement increasing. Stirrups also
plays an important role in resisting the shear loads. The spacing of the
stirrups should be limited to prevent the spalling of the concrete cover
around the longitudinal reinforcement.
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Conclusions The precast shear wall structure with rebars spliced by grouted
couplers(PSWGC) exhibited excellent seismic performance. No visible
damage concentrated on the joints connecting precast members. The
window belly wall, which was precast with wall limbs as a whole,
significantly affected crack patterns of the lower coupling beams under
large drift. The composite effect between the window belly wall and the
lower coupling beams should be carefully considered in structure design.
Replaceable steel coupling beam is a feasible way for improving seismic
performance of deep RCCBs in a CSW structure. Design philosophy and
detailing method have been proposed.
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Thanks much for your attention!
2019/6/28