Current Status & Plan for Future Work

1. NEES-CABER MEETING 11/02/2009 Current Status & Plan for Future Work

2. OUTLINE • PROGRESS OVERVIEW • MAJOR FINDINGS • EXPERIMENTAL STUDY • ANALYTICAL STUDY • FUTURE WORKS

3. I. Missouri S&T : Progress Overview

4. II. MAJOR FINDINGS : Circular Columns • Effect of Combined Loading • Reduction in torsional and bending strength • Rapid degradation of torsional stiffness compared to flexural stiffness • Effect of Increased Spiral Reinforcement Ratio • More confinement and lesser degradation of flexural and torsional strength • Increased energy dissipation capacity under flexural and torsional hysteresis • Effect of Reduction in Shear Span • No reduction in bending and torsional strength due to predominant flexural failure mode caused by low longitudinal ratio • Decrease of energy dissipation capacity and equivalent damping ratio

5. II. MAJOR FINDINGS : Square Columns • Out-of-plane Warping Effect • Investigation of the relationship between angle of twist and the curvature of the concrete struts from measured bidirectional movements at several specified cross sections • Investigation of variation of torsional rigidity along the height • Effect of Increased Transverse Reinforcement Ratio • Rectangular and octagonal ties provide adequate confinement to core concrete

6. H/D(3)-T/M(0)- 1.32/2.10 H/D(3)-T/M(0.2)- 1.32/2.10 H/D(6)-T/M(0.2)- 1.32/2.10 H/D(3)-T/M(0.4)- 1.32/2.10 H/D(6)-T/M(0.4)- 1.32/2.10 H/D(6)-T/M(0.4)- 0.73/2.10 Circular Columns not Tested as Parameters were not considered to be immediate priority H/D(6)-T/M(0)- 1.32/2.10 H/D(6)-T/M(0.4)- 1.32/2.10 H/D(6)-T/M(0.2)- 1.32/2.10 III. EXPERIMENT : Test Matrix in Proposal Moderate Details Trans. Ratio- 0.73% High Details Trans. Ratio- 1.32% Low Shear H/D=6 High Shear H/D=3 Level 1 Axial 7% Level 2 Axial 15% Under Progress H/D(6)-T/M(0.4)- 0.73/2.10

7. III. EXPERIMENT : Considered Test Parameters Circular Columns • T/M Ratio : 0, 0.1, 0.2, 0.4, and ∞ • M/V Ratio : 6 and 3 • Spiral Ratio (Low and Moderate) : 0.73 % and 1.32 % • Axial Load Level 2 : 7 % and 11 % (for one specimen) Square/Rectangular Columns (Critical Parameters) • Aspect Ratio : 6 (Previous study:1.5 ~ 6.5) • Transverse Reinforcement Ratio : 1.32% (Previous study: 0.1 % ~ 4 %) • Longitudinal Reinforcement Ratio : 2.13% (Previous study:1.0 % ~ 3.5 %) • Axial Load Ratio : 7% (Previous study: 5% ~ 50%) • Transverse Confinement Figuration

8. III. EXPERIMENT : Comparison of Test Parameters

9. III. EXPERIMENT : Circular Column (Match) Tests Completed But not in Proposal Tests Not Completed in Proposal Testing Done

10. III. EXPERIMENT : Square Column (Match) Tests Not Completed in Proposal Testing Done Tests Completed But not in Proposal

11. III. EXPERIMENT : Test Results of Square Columns Pure Flexure Pure Torsion

12. III. EXPERIMENT : Test Results of Square Columns Combined Loading • Significant degradation in flexural strength and stiffness with increasing T/M ratio • Rapid degradation in torsional strength and with decreasing T/M ratio in both circular and square columns • The difference in ultimate strength between positive and negative sides in square columns is less than circular column as there is no locking and unlocking effect.

13. IV. ANALYSIS : Flexure (Plastic Hinge Model) Circular Columns H/D=6, Spiral=0.73% V Lp p y Plastic Hinge Based Model

14. IV. ANALYSIS : Flexure (Plastic Hinge Model) Square Columns H/D=6, Hoop=1.32% V Lp p y Plastic Hinge Based Model

15. IV. ANALYSIS : Pure Torsion (STM) Square Columns H/D=6, Hoop=1.32% STM Analysis

16. IV. ANALYSIS : T-M-V Interaction (Circular Column) Elfgren (1972) Formula

17. Circular-Spiral Ratio-0.73% Circular-Spiral Ratio-1.32% T/M=0.4 T/M=0.2 T/M=0.1 IV. ANALYSIS : Projection of T-M Interaction Comparison 450 Square-Trans. Ratio -1.32% 400 350 Analytical Predictions 300 250 T (kN-m) T/M=0.6 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 1000 M (kN-m)

18. V. FUTURE WORK : Test of Remaining Square Column 1. Sequential Loading

19. V. FUTURE WORK : Test of Remaining Square Column 1. Sequential Loading • Torsional and bending loads are applied in sequence to evaluate the decoupled stiffness and strength degradation. • As of now, Missouri S&T has no feedback system to realize the exact displacement control. After load control, it is difficult to maintain the T/M ratio in sequential loading.

20. V. FUTURE WORK : Test of Remaining Square Column 2. Pure Torsion with Higher Axial Force Kawashima Missouri S&T • Pure Torsion under Low Axial Load • Pure Torsion without Axial Load • Pure Torsion under Medium Axial Load (7%) • Pure Torsion under High Axial Load (14%) • Maximum Torque Without Axial Load Decreased 10% Compared To With Axial Load • Stiffness Degradation More If Without Axial Load • Maximum Torque And Stiffness Degradation Shall Be Improved • Better Energy dissipation • Different Crack Development Pattern

21. μ=4 μ=3 Force Displacement μ=2 μ=1 75%Fy 50%Fy 25%Fy Load control Displacement control V. FUTURE WORK : Test of Remaining Square Column 3. Unidirectional Cyclic Combined Loading

22. V. FUTURE WORK : Test of Remaining Square Column 3. Unidirectional Cyclic Combined Loading • To test at T/M=0.4 in unidirectional cyclic load to decouple the effect of cracking in both the directions. Also, there is no locking and unlocking effect for square columns. • To compare the different crack patterns, strength and stiffness degradation with cyclic loads on both the directions. • Final failure mode will be somewhat different

23. V. FUTURE WORK : Test of Remaining Square Column 4. Combined Loading with Higher Axial Load • Axial load ratio significantly affect both the flexural and torsional response. • If higher axial load is applied, the damage sequence of specimen might be different. For example, the yielding sequence of longitudinal bar and transverse bar. • The inclination of crack will be different.

24. V. FUTURE WORK : Oval Columns Parameters Considered in Literature • Horizontal distance between the centers of two spirals : 1.0d ~ 1.5d • Aspect Ratio (H/B) : 1.5 ~ 6 • Spiral Reinforcement Ratio : 0.12% ~ 1.78% • Longitudinal Reinforcement Ratio : 1.0 % ~ 3.0% • Axial Load Ratio : 5% ~ 12 % • Size and Spacing of Longitudinal Bars in the Interlocking Region • Failure Mode : Shear failure & Flexural failure • Strong Axis and Weak Axis

25. V. FUTURE WORK : Comparison of Test Parameters

26. V. FUTURE WORK : Design of Oval Columns Longitudinal Section Cross Section

27. V. FUTURE WORK : Combined Loading Pure Torsion Pure Bending-shear Four specimens complete the interaction diagram for combined loading

28. V. FUTURE WORK : Bilateral Cyclic Loading Three components of ground motions during earthquake In practice Two lateral components in the weak and strong axes independently. Zahn et al 1983 Kawashima et al 1992, For flexural strength and ductility capacity bilateral excitation＜ unilateral excitation Week axis Strong axis Current design flexural strength and ductility capacities are overestimated P1 P2 Unilateral excitation Unilateral excitation P P1 ＞P2 P’1 = P*cosθ P’2= P*sinθ P’1 ＜ P1 & P’2 ＜ P2 P’2 P’2 /P’1 = tanθ θ is determined by flexural capacity about strong and week axis θ P’1 Bilateral excitation

29. V. FUTURE WORK : Test Matrix of Oval Columns Determined by test results of specimen 1 and specimen 5

30. V. FUTURE WORK : Matching with Proposal Tests planned to be Completed But not in Proposal Tests Not planned to be Completed in Proposal Testing Planned

31. V. FUTURE WORK : Fabrication Steel Cage Formwork

32. V. FUTURE WORK : Loading Setup Pure Torsion And Pure Flexural Loading(Weak Axis) Pure Flexural (Strong Axis) And Combined Loading Bilateral Loading

33. V. FUTURE WORK : Tentative Test Schedule

34. Thank You!