Experimental and numerical study on seismic behavior of reinforced concrete shear walls with bulging-induced defects

To examine the effect of bulging-induced defects on seismic behavior of reinforced concrete (RC) shear walls, one intact specimen and two specimens with varying degrees of defects were designed. Quasi-static tests were conducted to examine and compare the failure modes, hysteretic curves, load-bearing capacity, stiffness degradation, and energy dissipation capacity of the specimens. The results indicated that bulging-induced defects altered the crack propagation and failure modes of RC shear walls. Cracks tended to develop along the defects, and increased defect severity led to a transition from flexure-shear failure to brittle diagonal tension failure, attributed to the elevated diagonal principal tensile stress caused by section weakening and stress concentrations at the defect edges. Bulging-induced defects reduced the load-bearing and deformation capacities of the specimens. Specifically, in comparison to specimen SW-0, specimen SW-2, which exhibited the most severe defect, experienced reductions of 13.9% and 15.5% in yield load and peak load, respectively. Similarly, the yield, peak, and ultimate displacements declined by 21.7%, 30.7%, and 23.5%, respectively. To further explore the effects of defect ratio on seismic performance of shear walls, a numerical model incorporating defects was developed using OpenSees. A mathematical model was established to describe the relationship between defect ratio and peak load-bearing capacity. Based on the defect-integrated model, the influence of axial compression ratio and aspect ratio was also investigated. The simulation results revealed that as the defect ratio increased, both load-bearing capacity and deformation capacity declined significantly, with the peak load-bearing capacity decreasing by nearly 40% as the defect ratio increased from 2% to 10%. Additionally, a higher axial compression ratio improved load-bearing capacity but significantly reduced ductility and conversely, increasing the aspect ratio decreased the capacity while enhancing deformability.