Seismic behavior of non-seismically designed shear walls with moderate shear span under high axial loads

Abstract

This study investigates the seismic behavior of reinforced concrete (RC) non-seismically designed shear walls with moderate shear span-to-length ratios (SLR), while being subjected to high axial loads. Four shear wall specimens were fabricated and tested, including three specimens with an SLR of 1.58 and one with an SLR of 2.0. The applied axial load ratios (ALR) ranged from 0.30 to 0.35. Detailed test results, such as crack patterns, failure modes, hysteresis curves, stiffness degradation, and energy dissipation, are presented and analyzed. The test results show that all specimens, with different shear-to-flexure strength ratios (SFSR), experienced axial failure and were unable to sustain the target axial load at the end of the test. Among these specimens, three with SFSR values ranging from 0.82 to 1.24 failed in axial failure, while the specimen with an SFSR of 0.44 initially experienced shear failure, followed by axial failure after completing half a cycle. This indicates that SFSR has a significant effect on the failure mode of the shear walls under high ALR. Additionally, the test results obtained in this study are compared with the results of a previous study, in which test specimens had identical reinforcement detailing as in this study but were subjected to lower axial loads (ALR = 0.15–0.20), to investigate the effect of ALR on seismic behavior of shear walls in terms of failure mode, hysteretic curves. The observations show that for specimens with relatively higher SFSR (≥ 0.8), a high level of ALR not only affects the failure mode but also diminishes their deformability. In contrast, for the specimen with a low SFSR (0.44), the effect of ALR on deformability is minimal. Finally, a criterion for determining the occurrence of axial failure in shear walls is proposed.