Nonlinear and Code Analyses of PT Slab-Column Connections

Transcription

1 Nonlinear and Code Analyses of PT Slab-Column Connections Thomas Kang, Ph.D., P.E., Assistant Professor Yu Huang, Research Assistant The University of Oklahoma, Norman (Funded by OTCREOS and the University of Oklahoma)

2 Introduction Punching Shear Failure Study Aim PT slab-column connection Courtesy: J. Brink (DCI Engr.)

3 Introduction Punching Shear Failure Study Aim Punching shear failure at slab-column connection (Tian et al, 2008)

4 Introduction Punching Shear Failure Study Aim Punching shear failure at PT slab-column connections under earthquake simulations Kang and Wallace (ACI SJ 2005, ACI SJ 2006, PTI 2008) Kang et al. (ASCE JSE 2009, ACI CI 2007)

5 Introduction Punching Shear Failure Study Aim ACI punching shear provisions

6 Introduction Punching Shear Failure Study Aim ACI punching shear provisions Need to evaluate (PT edge/corner conn.) r

7 Introduction Punching Shear Failure Study Aim Objectives of this study 1. Revisit & evaluate ACI Review of experimental studies 3. Numerical simulations

8 Experimental Research Kang and Huang (2010) Modelled by Univ. of Oklahoma Foutch et al. (1990) at University of Illinois at Urbana-Champaign

9 Experimental Research PT edge connections Kang and Huang (2010) Analyzed by Univ. of Oklahoma Foutch et al. (1990) at University of Illinois at Urbana-Champaign

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

11 Experimental Research Tests used for nonlinear FE modeling 1. Tian et al., 2008 Two interior RC connections 2. Foutch et al., 1990 Four edge PT connections w/ f c = 6~7.3 ksi 3. Martinez-Cruzado et al., 1994 Two corner PT connections w/ f c = 5.9~6.1 ksi Two edge PT connections w/ f c = 4.6~4.8 ksi

12 Nonlinear FEM Analysis Modeling Details Modeling details Verification Unbonded tendon-concrete interactions

13 Nonlinear FEM Analysis Modeling Scheme Modeling details Verification Edge connection mesh Corner connection mesh

14 Nonlinear FEM Analysis Modeling scheme Modeling Details Verification Detailed information will be available at: 1. Kang and Huang, 2010 (in-press) PTI Journal, V. 8, No. 1, June Huang et al., 2010 (in-press) International Journal of Theoretical and Applied Multiscale Mechanics, 2010

15 Nonlinear FEM Analysis Modeling scheme Modeling details Moment vs. deflection (drift) - PT edge connections (S1, S3) Verification

16 Nonlinear FEM Analysis Modeling scheme Modeling details Moment vs. deflection (drift) - PT edge connections (S2, S4) Verification

17 Nonlinear FEM Analysis Modeling scheme Modeling details Verification Tendon stress increase vs. moment S1 S2 and S3 S4 Moment vs. Tendon stress increase

18 Nonlinear FEM Analysis Modeling scheme Modeling details N-S lateral force vs. drift ratio - PT corner connection (C2) Verification Analysis Experimental backbone

19 Nonlinear FEM Analysis Modeling scheme Modeling details Verification Data retrieve (edge) Stress reading illustration

20 ACI Code Analysis Numerical punching shear strength (Edge connection, S2) v u vs. deflection (drift)

21 ACI Code Analysis Numerical punching shear strength (Edge connection, S3) v u vs. deflection (drift)

22 ACI Code Analysis Prediction vs. ACI 318 RC nominal shear strength (PT edge connections, Foutch et al., 1990) 250% Average 154% & 178% 200% 150% 100% 50% ACI nominal shear strength 0% s1 s2 s3 s4 average Vu_AB Vu_CD

23 ACI Code Analysis Prediction vs. ACI 318 RC nominal shear strength (PT corner connections, Martinez-Cruzado et al., 1994) 250% Average 168% 200% 150% 100% 50% ACI nominal shear strength 0% c1a c1a' c1b c1b' c2a c2a' c2b c2b average Experimental Analysis

24 ACI Code Analysis Prediction vs. ACI RC nominal shear strength (PT corner connections under amplified gravity loads) 200% 180% Average 146% 160% 140% 120% 100% 80% ACI nominal shear strength 60% 40% 20% 0% c1a-2.5 c1a-2.5' c1b-2.5 c1b-2.5' c2a-2.5 c2a-2.5' c2b-2.5 c2b-2.5 average Analysis

25 ACI Code Analysis Unbalanced moment transfer ACI equation If critical section is close to square, around 40% unbalanced moment is transferred by the eccentric shear stress.

26 ACI Code Analysis The factor γ v can be obtained using numerical results of v u and experimental V sw, M sw, V applied, (V applied x l ) 1. v u_ab (monitored at front corner) 2. v u_cd (monitored at back corner)

27 ACI Code Analysis Unbalanced moment transfer (Edge connection; Foutch et al., 1990) γ v vs. Deflection or drift ratio (S1)

28 ACI Code Analysis Unbalanced moment transfer (Edge connection; Foutch et al., 1990) γ v vs. Deflection or drift ratio (S2)

29 ACI Code Analysis Unbalanced moment transfer (Corner connection; Martinez-Cruzado et al., 1994) γ v vs. Drift ratio (C2 & C2-2.5)

30 ACI Code Analysis Unbalanced moment transfer (Corner connection; Martinez-Cruzado et al., 1994) γ v vs. Drift ratio (C2 & C2-2.5)

31 Summary & Conclusions 1. Finite Element Model Development 2. Nonlinear Finite Element Analysis (FEA) 3. Evaluation of ACI 318 based on Exp. Data & FEA 1. Maximum shear stress vs. Nominal shear strength vs. 2. Assessed γ v (~0.2) vs. Specified γ v (~0.4) 3. For both PT edge and corner connections 4. f c = 4.9 ksi limitation could be increased to 6 ksi.

32 Questions & Answers Four Seasons PT Flat Plate Building punching shear failure around drop panel during 1994 Northridge EQ; now demolished