Title:
Strain Nonlinearity and Shear Lag Effect in Compressive Flange of Reinforced Concrete Structural Walls
Author(s):
Zhongwen Zhang, Da Luo, and Bing Li
Publication:
Structural Journal
Volume:
118
Issue:
3
Appears on pages(s):
199-208
Keywords:
flanged reinforced concrete walls; reinforced concrete (RC); seismic; shear lag effect
DOI:
10.14359/51729359
Date:
5/1/2021
Abstract:
Contrary to the plane section assumption, nonlinearity in distribution of the vertical strains was commonly found in the compressive flange of structural reinforced concrete (RC) walls, making their compression contact area, neutral depth, and maximum compressive strain often vary significantly from the calculated values. For shear-dominated flanged walls, these factors are crucial in accurately estimating their ultimate strength. The uneven distributions of the vertical compressive strains in the flange relates to the shear lag effect and plastic yielding of the reinforcing bars. This paper investigates this phenomenon with the existing experimental data and numerical models. For walls with a monotonic lateral load, the nonlinearity was found to be mainly caused by the compressive shear lag effect. The existing method relating the effective width linearly with height of the wall was found to be inaccurate and a modified theoretical method was proposed. For walls going through cyclic lateral loads, the nonlinearity was found to be strongly related to tension yielding of the reinforcing bars in previous loading reverses. An empirical equation was proposed. The results indicate higher contribution of the compressive flange in squat RC walls than anticipated by the current design practice. However, the contribution can be severely hindered by the previous tension yielding of the flange.
Related References:
1. Gulec, C.; Whittaker, A.; and Stojadinovic, B., “Peak Shear Strength of Squat Reinforced Concrete Walls with Boundary Barbells or Flanges,” ACI Structural Journal, V. 106, No. 3, May-June 2009, pp. 368-377.
2. Gulec, C. K., and Whittaker, A. S., “Empirical Equations for Peak Shear Strength of Low Aspect Ratio Reinforced Concrete Walls,” ACI Structural Journal, V. 108, No. 1, Jan.-Feb. 2011, pp. 80-89.
3. Kassem, W., “Shear Strength of Squat Walls: a Strut-And-Tie Model and Closed-Form Design Formula,” Engineering Structures, V. 84, 2015, pp. 430-438. doi: 10.1016/j.engstruct.2014.11.027
4. Ma, J.; Ning, C.; and Li, B., “Peak Shear Strength of Flanged Reinforced Concrete Squat Walls,” Journal of Structural Engineering, ASCE, V. 146, No. 4, 2020, p. 04020037. doi: 10.1061/(ASCE)ST.1943-541X.0002575
5. Palermo, D.; Vecchio, F. J.; and Solanki, H., “Behavior of Three-Dimensional Reinforced Concrete Shear Walls,” ACI Structural Journal, V. 99, No. 1, Jan.-Feb. 2002, pp. 81-89.
6. Thomsen, J. H. IV, and Wallace, J. W., “Displacement-Based Design of Slender Reinforced Concrete Structural Walls—Experimental Verification,” Journal of Structural Engineering, ASCE, V. 130, No. 4, 2004, pp. 618-630. doi: 10.1061/(ASCE)0733-9445(2004)130:4(618)
7. Zhang, Z., and Li, B., “Shear Lag Effect in Tension Flange of RC Walls with Flanged Sections,” Engineering Structures, V. 143, 2017, pp. 64-76. doi: 10.1016/j.engstruct.2017.04.017
8. Paulay, T., and Priestley, M. N., Seismic Design of Reinforced Concrete and Masonry Buildings, Wiley Interscience Publication, New York, 1992, 768 pp.
9. Song, Q. G., and Scordelis, A. C., “Formulas for Shear-Lag Effect of T-, I-and Box Beams,” Journal of Structural Engineering, ASCE, V. 116, No. 5, 1990, pp. 1306-1318. doi: 10.1061/(ASCE)0733-9445(1990)116:5(1306)
10. Chang, S. T., and Zheng, F. Z., “Negative Shear Lag in Cantilever Box Girder with Constant Depth,” Journal of Structural Engineering, ASCE, V. 113, No. 1, 1987, pp. 20-35. doi: 10.1061/(ASCE)0733-9445(1987)113:1(20)
11. Chang, S. T., and Yun, D., “Shear Lag Effect in Box Girder with Varying Depth,” Journal of Structural Engineering, ASCE, V. 114, No. 10, 1988, pp. 2280-2292. doi: 10.1061/(ASCE)0733-9445(1988)114:10(2280)
12. Waugh, J. D., and Sritharan, S., “Nonlinear Analysis of T-Shaped Concrete Walls Subjected to Multi-Directional Loading,” 9th U.S. National Conference and 10th Canadian Conference on Earthquake Engineering, Toronto, ON, Canada, 2010, 1506 pp.
13. Zhang, Z., and Li, B., “Seismic Performance Assessment of Slender T-shaped Reinforced Concrete Walls,” Journal of Earthquake Engineering, V. 20, No. 8, 2016, pp. 1342-1369. doi: 10.1080/13632469.2016.1140097
14. Brueggen, B. L.; French, C. E.; and Sritharan, S., “T-Shaped RC Structural Walls Subjected to Multidirectional Loading: Test Results and Design Recommendations,” Journal of Structural Engineering, ASCE, V. 143, No. 7, 2017, p. 04017040. doi: 10.1061/(ASCE)ST.1943-541X.0001719
15. Hoult, R. D., “Shear Lag Effects in Reinforced Concrete C-Shaped Walls,” Journal of Structural Engineering, ASCE, V. 145, No. 3, 2019, p. 04018270. doi: 10.1061/(ASCE)ST.1943-541X.0002272
16. Kwan, A. K., “Shear Lag in Shear/Core Walls,” Journal of Structural Engineering, ASCE, V. 122, No. 9, 1996, pp. 1097-1104.
17. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
18. Hassan, M., and El-Tawil, S., “Tension Flange Effective Width in Reinforced Concrete Shear Walls,” ACI Structural Journal, V. 100, No. 3, May-June 2003, pp. 349-356.
19. Ni, X., and Cao, S., “Shear Lag Analysis of I-Shaped Structural Members,” Structural Design of Tall and Special Buildings, V. 27, No. 10, 2018, p. e1471 doi: 10.1002/tal.1471
20. Amadio, C.; Fedrigo, C.; Fragiacomo, M.; and Macorini, L., “Experimental Evaluation of Effective Width in Steel–Concrete Composite Beams,” Journal of Constructional Steel Research, V. 60, No. 2, 2004, pp. 199-220. doi: 10.1016/j.jcsr.2003.08.007
21. Zhang, Z., and Li, B., “Seismic Performance Assessment of Slender T-Shaped Reinforced Concrete Walls,” Journal of Earthquake Engineering, V. 20, No. 8, 2016, pp. 1342-1369. doi: 10.1080/13632469.2016.1140097
22. Eurocode 2, “Design of Concrete Structures—Part 1-1: General Rules and Rules for Buildings,” CEN EN 1992-1-1, Brussels, Belgium, 2004, 225 pp.
23. Nie, J. G.; Cai, C. S.; Zhou, T. R.; and Li, Y., “Experimental and Analytical Study of Prestressed Steel–Concrete Composite Beams Considering Slip Effect,” Journal of Structural Engineering, ASCE, V. 133, No. 4, 2007, pp. 530-540. doi: 10.1061/(ASCE)0733-9445(2007)133:4(530)
24. Fahmy, E. H., and Robinson, H., “Analyses and Tests to Determine the Effective Widths of Composite Beams in Unbraced Multi-Storey Frames,” Canadian Journal of Civil Engineering, V. 13, No. 1, 1986, pp. 66-75. doi: 10.1139/l86-010