state-of-the-art studies on the behavior of coupling beams · state-of-the-art studies on the...

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





• 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


10 2019/6/28

Experimental study on deep RCCBs in HKU (Kwan and Zhao , 2002).


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


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.


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


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


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


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


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


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


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


Lo

ad

(kN

)

-400

-300

-200

-100

0

100

200

300

400

0 0.005 0.01 0.015 0.02 0.025


Lo

ad

(kN

)

-400

-300

-200

-100

0

100

200

300

400

0 0.005 0.01 0.015 0.02 0.025


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





• 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


(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


-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


-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


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


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


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


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


Peak load

Failure

2019/6/28 Crack pattern and failure modes

28

CB25-1 CB25-2


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


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


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


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


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


CB15-3 292 367 5.43 11.94 26.44 2.20 4.86 Flexural


CB25-1 156 198 7.71 16.23 26.81 2.10 3.48 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


Specimen Vy

(kN)

Vu

(kN)

Ratation (10-3rad) Ductility ratio Failure mode

θy(rad) θu(rad) Θu1(rad) θu/θy θu1/θy



CB15-3 292 367 5.43 11.94 26.44 2.20 4.86 Flexural


CB25-1 156 198 7.71 16.23 26.81 2.10 3.48 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


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





• 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


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


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



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


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


2019/6/28

Crack pattern of the assembled RCCBs (Qian and Zhao, 2013)

A B C1 C2 E

41


-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


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


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


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


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


TGC

Lower precast wall

Single-row additional rebar

Web distributed rebar


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


Cast-in-situ topping

50

70

12

0

Precast wall

Additional RebarD8@200

Precast wall


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


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


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


(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


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





• 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


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


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


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


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


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


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


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


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


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

2019/6/28

• Background





• Conclusions

Outlines

75

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.

2019/6/28

76

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.

2019/6/28

77

Thanks much for your attention!

2019/6/28

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