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Nonlinear and Code Analyses of PT Slab-Column Connections
Thomas Kang, Ph.D., P.E., Assistant ProfessorYu Huang, Research Assistant
The University of Oklahoma, Norman
(Funded by OTCREOS10.1-21 and the University of Oklahoma)
Introduction
PT slab-column connection
Study AimPunching Shear Failure
Courtesy: J. Brink (DCI Engr.)
Introduction
Punching shear failureat slab-column connection
Study AimPunching Shear Failure
(Tian et al, 2008)
Introduction
Punching shear failureat PT slab-column connectionsunder earthquake simulations
Study AimPunching Shear Failure
Kang and Wallace (ACI SJ 2005, ACI SJ 2006, PTI 2008) Kang et al. (ASCE JSE 2009, ACI CI 2007)
r
Introduction
ACI 318-08 punching shear provisionsStudy AimPunching Shear Failure
Need to evaluate(PT edge/corner conn.)
IntroductionStudy Aim
1. Revisit & evaluate ACI 318-08
2. Review of experimental studies
3. Numerical simulations
Punching Shear Failure
Objectives of this study
Foutch et al. (1990) at University of Illinois at Urbana-Champaign
Experimental Research
Kang and Huang (2010) Modelled by Univ. of Oklahoma
Foutch et al. (1990) at University of Illinois at Urbana-Champaign
Experimental Research
Kang and Huang (2010) Analyzed by Univ. of Oklahoma
PT edge connections
Experimental Research
Tests used for nonlinear FE modeling
1. Tian et al., 2008Two interior RC connections
2. Foutch et al., 1990Four edge PT connections w/ f’c = 6~7.3 ksi
3. Martinez-Cruzado et al., 1994Two corner PT connections w/ f’c = 5.9~6.1 ksi Two edge PT connections w/ f’c = 4.6~4.8 ksi
Nonlinear FEM Analysis
Unbonded tendon-concrete interactions
Modeling detailsModeling Details Verification
Modeling detailsModeling Scheme
Edge connection mesh Corner connection mesh
Verification
Nonlinear FEM Analysis
Verification
Nonlinear FEM Analysis
Detailed information will be available at:
1. Kang and Huang, 2010 (in-press)PTI Journal, V. 8, No. 1, June 2010
2. Huang et al., 2010 (in-press)International Journal of Theoretical and Applied Multiscale Mechanics, 2010
Modeling DetailsModeling scheme
VerificationModeling scheme
Moment vs. deflection (drift)- PT edge connections (S1, S3)
Nonlinear FEM AnalysisModeling details
Verification
Moment vs. deflection (drift)- PT edge connections (S2, S4)
Nonlinear FEM AnalysisModeling scheme Modeling details
Verification
Tendon stress increase vs. moment
Moment vs. Tendon stress increase
S1 and S3S2 and S4
Nonlinear FEM AnalysisModeling scheme Modeling details
Verification
Experimental backbone
Analysis
Nonlinear FEM Analysis
N-S lateral force vs. drift ratio- PT corner connection (C2)
Modeling scheme Modeling details
Data retrieve (edge)
Stress reading illustration
Nonlinear FEM AnalysisModeling scheme Modeling details Verification
Prediction vs. ACI 318 RC nominal shear strength(PT edge connections, Foutch et al., 1990)
0%
50%
100%
150%
200%
250%
s1 s2 s3 s4 average
Vu_AB Vu_CD
ACI nominal shear strength
Average 154% & 178%
ACI Code Analysis
c1a c1a' c1b c1b' c2a c2a' c2b c2b average0%
50%
100%
150%
200%
250%
Experimental Analysis
ACI nominal shear strength
Average 168%
Prediction vs. ACI 318 RC nominal shear strength(PT corner connections, Martinez-Cruzado et al., 1994)
ACI Code Analysis
c1a-2.5 c1a-2.5' c1b-2.5 c1b-2.5' c2a-2.5 c2a-2.5' c2b-2.5 c2b-2.5 average0%
20%
40%
60%
80%
100%
120%
140%
160%
180%
200%
Analysis
ACI nominal shear strength
Average 146%
Prediction vs. ACI 318-08 RC nominal shear strength(PT corner connections under amplified gravity loads)
ACI Code Analysis
Unbalanced moment transfer
ACI 318-08 equation
If critical section is close to square, around 40% unbalanced moment is transferred bythe eccentric shear stress.
ACI Code Analysis
The factor γv can be obtained using numerical results of vuand experimental Vsw, Msw, Vapplied, (Vapplied x l’)
1. vu_AB (monitored at front corner)
2. vu_CD (monitored at back corner)
ACI Code Analysis
Unbalanced moment transfer(Edge connection; Foutch et al., 1990)
γv vs. Deflection or drift ratio (S1)
ACI Code Analysis
Unbalanced moment transfer(Edge connection; Foutch et al., 1990)
ACI Code Analysis
γv vs. Deflection or drift ratio (S2)
Unbalanced moment transfer(Corner connection; Martinez-Cruzado et al., 1994)
ACI Code Analysis
γv vs. Drift ratio (C2 & C2-2.5)
ACI Code Analysis
Unbalanced moment transfer(Corner connection; Martinez-Cruzado et al., 1994)
γv vs. Drift ratio (C2 & C2-2.5)
Summary & Conclusions
1. Finite Element Model Development
3. Evaluation of ACI 318 based on Exp. Data & FEA
2. Nonlinear Finite Element Analysis (FEA)
vs.
1. Maximum shear stress vs. Nominal shear strength
2. Assessed γv (~0.2) vs. Specified γv (~0.4)
3. For both PT edge and corner connections
4. f’c = 4.9 ksi limitation could be increased to 6 ksi.