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)

IntroductionStudy AimPunching Shear Failure

ACI 318-08 punchingshear provisions

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

Martinez-Cruzado et al. (1994) at University of California at Berkeley

Experimental Research

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

Numerical punching shear strength(Edge connection, S2)

vu vs. deflection (drift)

ACI Code Analysis

Numerical punching shear strength(Edge connection, S3)

ACI Code Analysis

vu vs. deflection (drift)

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.

Questions & Answers

Four Seasons PT Flat Plate Building –punching shear failure around drop panel

during 1994 Northridge EQ; now demolished