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PESDES 2017 International Workshop on Performance-Based Seismic Design of Structures
Prediction of the Lateral Load Displacement Curves for RC Squat Walls Failing in Shear
DirectorNational Center for Research on Earthquake Engineering
ProfessorNational Taiwan University
Shyh-Jiann Hwang
October 14, 2017
Mission of NCREE
• Established at National Taiwan University in 1990• Mission:
2
· Pre-quake preparation – Disaster prevention· Emergency response – Disaster reduction· Post-quake recovery – Disaster relief
Vulnerable Low-rise RC Buildings
Most Vulnerable Buildings under Chi-Chi Earthquake
Collapse of School Building
Collapse of Street Townhouse
Low-rise Reinforced Concrete Buildings
• Tax Information of Taiwan (2011)• Total: 54 million buildings,1,651million m2
• RC Buildings with 7 stories and below : 61.4%
RC Steel Brick Else
Tota
l Flo
or A
rea
Seismic EvaluationCapacity
Spectrum MethodPushover Analysis
Performance-Target Ground Acceleration Ap
Ap
Objective
Ø Propose the lateral-load displacement curves of shear wall and short column subjected to shear failures
Ø Considering:l crackingl strengthl shear deformationl collapse
2.Shear deformation
1.Shear cracking
4. gradual process
3. Strut-and-tie action
Li, Y. A., Huang, Y. T., and Hwang, S. J., (2014) “Seismic Response of Reinforced Concrete Short Columns Failed in Shear,” ACI Structural Journal, V. 111, No. 4, July-August, pp. 945-954.
Test Observation on Short Column
Proposed Curve
Weng, P. W., Li, Y. A., Tu, Y. S., and Hwang, S. J., (2017) “Prediction of Lateral Load Displacement Curves for Reinforced Concrete Squat Walls Failed in Shear,” Journal of Structural Engineering, ASCE, 143(10), DOI: 10.1061/(ASCE)ST.1943-541X.0001872, 04017141.
(ACI 318-14 Code)web shear cracking
flexural shear cracking
Cracking Point
wwccr
NddtfV4
27.0
dt
VM
tNf
fV ww
wwcw
ccr
2
2.01.005.0
effc
wcrcrf IE
hV12
3
,
, ,, slipc f c csr cr rr
dtEhV
wc
wcrcrs 4.0,
ws
yb
y
crcrslip h
kddufd
VV
1E8
2
,
Flexure
Shear
Slip
Cracking Point
v
d r
v
h
NormalStrain
2
h
Shear Strain 2
d
d
cf
cf
o o
HognestadParabola
d
d
d
r
Crackedreinforcedconcrete
vf
hf
Cylinder
d
d
d
Equilibrium
Diagonal Compression
Compatibility
Softening
Diagonal Comp. Failure
Hwang, S. J., and Lee, H. J., (2002) “Strength Prediction for Discontinuity Regions by Softened Strut-and-Tie Model,” Journal of Structural Engineering, ASCE, Vol. 128, No. 12, pp. 1519-1526.
Softened Strut-and-Tie Model
Hwang, S. J., Tsai, R. J., Lam, W. K., and Moehle, J. P., (2017) “Simplification of Softened Strut-and-Tie Model for Strength Prediction of Discontinuity Regions,” ACI Structural Journal, V. 114, No. 5, pp.
1239-1248.
cos strcn AfKV
wcww ft
Nkd
85.025.0
wstr tkdA
46.114.01cottan BK AA
112
c
y
ff
A
130
c
y
ff
B
52.035.3
MPafc
Strength PointSoftened Strut-and-Tie model
Shear Deformation due to Strain Field of Shear Element
1DL - 1.5% 1DH – 0.75% rd
v
h
Formulation of Strut-and-Tie Mechanism
Tests of Short Columns
※ Approximation of @ Vmax is preferred.
Vmax : convergent @Vmax : divergent
Characteristics of Strength Point
sn ipf sl
ws h 2sin006.0
Flexure
Shear
Slip
Lateral Displacement
effc
wcrf IE
hV12
3
ws
yb
y
crslip h
kddufd
VV
1E8
2
(Referred to ASCE 41-13 Table 10-20)
Collapse Point
Condition Strength ratio ( )
Drift ratio ( )
0.2 2.0%
0.0 1.0%
na VV wa h
05.0
cww
yss
ftNfAA
05.0
cww
yss
ftNfAA
• Hidalgo et al. (2002)Test Data of Shear Walls
Weng, P. W., Li, Y. A., Tu, Y. S., and Hwang, S. J., (2017) “Prediction of Lateral Load Displacement Curves for
Reinforced Concrete Squat Walls Failed in Shear,” Journal of Structural Engineering, ASCE, 143(10), DOI:
10.1061/(ASCE)ST.1943-541X.0001872, 04017141.
Comparison of Failure Mechanisms coscos, strcdSSTn AfKCV Proposed
ACI 318-14 , 0.83n ASCE c c y w wt w c wV f f t f t
Crushing of concrete
Widening of Diagonal crack
1.64 11
64%steel contributionconcrete contribution
232%0.83 10.25
steel contributionconcrete contribution
Li, Y. A., and Hwang, S. J., (2017) “Prediction of Lateral Load Displacement Curves for Reinforced Concrete Short Columns Failed in Shear,” Journal of Structural Engineering, ASCE,
143(2), DOI: 10.1061/(ASCE)ST.1943-541X.0001656, 04016164.
Speci. H/h[MPa] [MPa]
1DL
1
0.09 281.27% 430
1DH 0.29 25
1NL 0.10 230.24% 458
1NH 0.29 25
2DL
2
0.09 261.27% 430
2DH 0.30 24
2NL 0.10 230.24% 458
2NH 0.29 26
1
20.3
36 1.21% 300
3 391.88% 305
4 35
2 0.6 48 1.21% 300
cf cg fA
N
ytfs
Test of Short Columns
1. Proposed curve is trilinear, consisting of shear cracking, shear strength and collapse point
2. Proposed curve is suitable for shear walls and short columns
3. Approximation of strain field to calculate shear deformation is feasible
Conclusions
p Funded by Ministry of Science and Technology and National Center for Research on Earthquake Engineering (NCREE)
Acknowledgement