Lightly reinforced concrete structural walls with single layer: Effect of out-of-plane deformations on in-plane response

Lightly reinforced concrete walls with a single-layer of reinforcement have been frequently used as the lateral load-resisting system of industrialized and low-cost housing. The drift capacity of these walls is related to the tensile strain demand of the vertical rebars. The current approach for evaluation of this strain demand considers in-plane deformations only. Therefore, the effect of out-of-plane deformation and consequently the parameters controlling its development, such as the wall thickness, are not incorporated in the minimum reinforcement ratio requirements. This paper investigates the effect of out-of-plane deformation on the deformation capacity of thin, lightly reinforced structural walls. For this purpose, a numerical modeling approach, verified against existing experimental results, has been used to conduct parametric studies on the boundary zones with different dimensions and rebar ratios. The results show progression and recovery of significant out-of-plane deformation (before the development of out-of-plane instability) during in-plane loading of relatively thin walls and consequently a noticeable increase in strain demand of vertical bars, which would reduce the walls' deformation capacity. Also, the correlation between the rebar ratio and cross-sectional dimension of the boundary zone and anticipated rebar plastic strain is investigated, and importance of three-dimensional response assessment of slender shear walls with single-layer reinforcement is emphasized.