simple strut model for evaluating infill-frame...

Simple strut model for evaluating infill-frame interaction

Yasushi SANADA, Osaka Univ., Japan

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By Padang Ekspres

Modelate

damage

Yasushi SANADA, Toyohashi Univ. of Tech., Japan

2007 Sumatra earthquakes of 8.4 and 7.9 ML

Test and Analysis of a Masonry Infill Wall

Used in Indonesia

at Tongji Univ. in Sep. 2011

Structural type

*3-story

*R/C with Brick Infill Walls

*3-story


Structural type

Comparisons between collapsed/moderately damaged buildings


*E0=0.15 to 0.20

*E0=0.15 to 0.20

according to Japanese standard



Used in Indonesia


Structural type

*3-story


*3-story


Damage level

Damage level Structural type

*Collapse

*Moderate

Why?



*E0=0.15 to 0.20

*E0=0.15 to 0.20




Used in Indonesia


Damage level

Damage level

*Collapse

*Moderate

Why? Amount of Brick Infill?



Conclusion

Brick Infill contributed to the seismic

performance of buildings

Smaller

Larger


Used in Indonesia


Preparation of R/C frame specimen

Experimental Approach

φ4@100

700

55

01

,00

0600

2,1

50

700

325 800 800 3002,250

100

140

140

1214-φ9

4-φ9

φ4@100Lower beam

a'

a

a-a'

b-b'

b b'

Upper beam

D10

12-D19

12-D19

D10

2 x 40%-scale R/C one-bay

frame specimens,

representing 1st-story of the

surviving building

Uppre beam

Lower beam

Mortar20mm

Brick Wall 140mm

a'

a

70

0550

1,0

00

600

70

0

325 800 800 3002,250

2,1

50

a-a'

Preparation of R/C frame specimen

φ4@100

700

55

01

,00

0600

2,1

50

700

325 800 800 3002,250

100

140

140

1214-φ9

4-φ9

φ4@100Lower beam

a'

a

a-a'

b-b'

b b'

Upper beam

D10

12-D19

12-D19

D10

Brick wall


Preparation of brick wall specimen

Cutting from moderately

damaged building




damaged building

Transporting to

Toyohashi Univ.


Transported

Infill


damaged building

Transporting to

Toyohashi Univ.


Seismic

Testing


Test set-up and loading program

Test set-up

Loading program

– Vertical loading: Constant (183.4 kN)

– Horizontal loading: Cyclic (1/8001/12.5)

EastWest

PositiveNegative

2000 kN Vertical jacks 1000 kN Horizontal jack

West East

1750

450

400 Steel Box

Steel Box


-200

-100

0

100

200

-2 -1 0 1 2

Lat

eral

For

ce(k

N)

Drift Ration (%)

柱の曲げひび割れ

BF

Qmin = -34.5 kN

Qmax = 36.75 kN

Lateral force vs. drift ratio

Infilled Frame R/C Bare Frame


-200

-100

0

100

200

-2 -1 0 1 2Lat

eral

For

ce (kN

)

Drift Ration (%)

柱、壁の分離


壁のせん断ひび割れ

柱のせん断ひび割れ

主筋の降伏

帯筋の降伏

柱のせん断破壊

△

▲

×

IFQmax = 163.5 kN

Qmin = -174 kN

△

▲

×

-200

-100

0

100

200

-2 -1 0 1 2

Lat

eral

For

ce(k

N)

Drift Ration (%)


BF

Qmin = -34.5 kN

Qmax = 36.75 kN




Comparison of performance curves

-200

-150

-100

-50

0

50

100

150

200

-10 -7.5 -5 -2.5 0 2.5 5 7.5 10

La

tera

l fo

rce

(kN

)

Drift ratio (%)

QIF=174.0kN

QBF=28.5kN

2.8% 1.6%


Damage level

Damage level

*Collapse

*Moderate


Conclusion

Brick Infill contributed to the seismic

performance of buildings


Used in Indonesia


Simple strut model for evaluating infill-frame interaction

Yasushi SANADA, Osaka Univ., Japan

W = 0.25 dm (Paulay and Priestley)

cos

-1 W

c hc

αc : the ratio of the column contact length to the

height of the column (El-Dakhakhni et al.)

Strut width w:

dm

H h

Introduction

Strut Model

where 4.0175.0

hW (Stafford-Smith and Carter)

mgc

m

hIE

tE

4

2sin

Modeling of Infilled Frame

Strut width (W) = ? Contribution of infill to

strength/stiffness

Infill

deformation : iδ Column

deformation: cδ Infilled frame

deformation

Flexural

deformation

Shear

deformation

Frame/Infill

contact length

Infilled frame

Q

y: intersection point

iδ = cδ

yhs

h

Ch hs

cδ

Q

Mu

Qu

Evaluation of cδ

Moment

diagram

Column

Displacement: cδ(y)

432 ..24/1..6/1..2/11

yCyQyMIE

y huu

cc

c 0 ≤ y ≤ hs.

Column displacement:

)(2

2

yMdy

xdEI )(yxEI

Double Integration

hs θ

hs

h

Ch

fm

f 'm

=

fm

Q

Cs

wh

L

hs

h

Ch

fm

f 'm

=

fm

Q

Cs

wh

L

f’m = 0.65 fm

Equivalent

stress block

Evaluation of cδ

Moment

diagram

Column

Displacement: cδ(y)

)(2

2

yMdy

xdEI )(yxEI

Double Integration

yhs

h

Ch hs

cδ

Q

Mu

Qu

θ=0

Column displacement:

hs ≤ y ≤ h :

)..24/1..6/1

...4/1.2/1...6/1(1

43

223

shsh

shuhu

cc

c

hCyhC

yhCMyhCQIE

y

iδ

θ

θ

Infill : uniform shear deformation

yy ii

h

hyci

Evaluation of iδ

yy ic

Finding intersection height

(Newton Raphson Method)

hs

hs: Infill/frame contact length w = hs cos θ

Infill/Frame Contact Length

hs : intersection height

yy ic

Finding intersection height

(Newton Raphson Method)

hs: Infill/frame contact length

Infill/Frame Contact Length

hs : intersection height

w = hs cos θ 2

-200

-100

0

100

200

-2 -1 0 1 2Lat

eral

For

ce (kN

)

Drift Ration (%)

柱、壁の分離




主筋の降伏

帯筋の降伏


△

▲

×

IFQmax = 163.5 kN

Qmin = -174 kN

△

▲

×

-200

-100

0

100

200

-2 -1 0 1 2

Lat

eral

For

ce(k

N)

Drift Ration (%)


BF

Qmin = -34.5 kN

Qmax = 36.75 kN



Application to Test Specimen

Evaluation of Infill Contribution

-200

-100

0

100

200

Lat

eral

for

ce (

kN)

-2 -1 0 1 2

Drift ratio (%)

Experiment

IF_FB

-200

-100

0

100

200

-2 -1 0 1 2

Lat

eral

For

ce (kN

)

Drift Ration (%)

柱、壁の分離




主筋の降伏

帯筋の降伏


△

▲

×

IFQmax = 163.5 kN

Qmin = -174 kN

△

▲

×

-200

-100

0

100

200

-2 -1 0 1 2

Lat

eral

For

ce(k

N)

Drift Ration (%)


BF

Qmin = -34.5 kN

Qmax = 36.75 kN

Lateral force at the same drift ratio

2cos..

d

twEK m

hs= 312 mm

Strut width : Initial lateral stiffness of infill:

hs = y

w = 2 hs cos

= 515 mm

Contact length:

= 112.6 kN cos... mftwQ

Verification of Analytical Model

Lateral strength of infill:

-200

-100

0

100

200

Lat

eral

for

ce (

kN)

-2 -1 0 1 2

Drift ratio (%)

Analysis

Experiment

Seismic Performance of Infilled R/C Frame

Q

Cs

hs

h

Ch

Cs/2 cos θ Qu

Qt Qu

Qt

-300

-200

-100

0

100

200

300

Lat

eral

for

ce (

kN)

-4 -2 0 2 4

Drift ratio (%)

Test Model

tsu QCQQ cos2/

Lateral strength of

overall infilled frame:

Conclusions

A simplified analytical method was proposed to evaluate infill

contribution to the seismic performance of masonry infilled RC frames,

and was verified through our structural test.

In the proposed analytical method, an infill panel is replaced by a

diagonal compression strut.

Compression strut width was determined with contact length between

column and infill.

Contact length was evaluated based on the compression balance at the

infilled/frame interface and lateral displacement compatibility under

column flexural and infill shear deformations.

The performance curve of the infill in the experimental specimen was

simulated by the proposed method. Consequently, a good agreement was

observed between experimental and analytical results.

Thank you for your attention

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