Evaluation of shear models and seismic performance of RC columns under the constant/variable axial loads

Abstract:

Under strong vertical earthquakes near-fault lines, significant variable axial forces generated in bridge RC columns may weaken the shear resistance of RC column and even lead to shear failure. However, current research both domestically and internationally typically focuses the influence of vertical ground motion on seismic performance of RC columns based on fiber models, neglecting the shear degradation performance of the columns. Alternatively, studies based on shear models derived from fixed axial force assumptions investigate the effects of complex variable axial forces on the seismic performance of columns under strong vertical seismic actions. This leads to substantial differences in conclusions drawn from various shear models. In this context, based on quasi-static cyclic loading column model tests under constant and variable axial load, the accuracy of three representative shear models is evaluated, including one strength-based model and two deformation-based failure models, and a suggested model was provided. Moreover, a new numerical quasi-static loading test under constant and variable axial load is designed to study the effect of variable axial load on the seismic performance of RC column. Results indicate that the seismic performance of columns obtained by using different shear failure models show great disparity, especially for the case of variable axial load. The influence of variable axial loads focuses on the seismic performance of RC column mainly manifests in earlier initiation of shear failure and severer shear degradation. This paper provides valuable insights for simulating the shear performance of columns under variable axial loads, offering a theoretical basis for the seismic evaluation and design of RC columns located in the near-fault region.