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.