Seismic performance and damage properties of flexure-shear critical RC columns with various loading cycles

Abstract

An experimental study was conducted to investigate the effects of loading cycles on seismic behavior and damage properties for flexure-shear critical reinforced concrete columns. Two groups of circular columns (including 8 specimens) with different shear span ratios were tested under quasi-static loads with various cycles, and the numbers of load cycle were designed as 0 (i.e., monotonic loading), 3, 10, and 20 cycles, respectively. The failure modes, load-deformation curves, ductility and energy dissipation capacity of the flexure-shear critical columns with various loading cycles were explored. Test results revealed that the shear effects and cumulative damage effects induced by cyclic loading are intensified with the increase of the loading cycles, which demonstrated that the columns are prone to occur the flexure-shear failure with the increase of the cycles. The study examined that the ultimate deformation is the most crucial factor affecting the damage properties of flexure-shear critical columns. The ultimate displacement diminishes with the loading cycles increase, and it reduces by 38%, 50%, and 62%, respectively, when the loading cycles increase from 0 to 3, 10, and 20 cycles. Additionally, the damage properties of flexure-shear critical columns are also pertinent to cumulative energy dissipation. The cumulative energy dissipation of column specimens increases obviously after yielding and increases with the loading cycles increase. An new two-parameter seismic damage model considering ultimate deformation and energy dissipation that including the effects of loading cycles was proposed, and the model could optimally analyze the damage properties of flexure-shear critical columns subjected to seismic excitation.