Experimental investigation and load-deformation analysis of reinforced concrete bridge columns under various loading cycles

Abstract

Twenty reinforced concrete (RC) bridge columns were tested under constant axial compressive as well as cyclic lateral loading, to explore the effect of loading cycle numbers (3, 10, 20 cycles for a given displacement amplitude) on the seismic behavior of RC bridge columns. Test results demonstrate that the bridge column specimens under cyclic loading failed in flexural-shear mode, which was evident by the presence of diagonal cracks, buckled longitudinal reinforcement, fractured stirrup, as well as saliently pinched lateral force–displacement hysteretic curves. As the axial compression ratio increased from 0.05 to 0.15 at the aspect ratio 1.6, there was about 50% increase in their yield and peak strengths, significant decrease in ultimate displacement, and about 30% decrease in the displacement ductility in the RC bridge columns. As the aspect ratio decreased from 2.3 to 1.6 at the axial compression ratio 0.05, there was about 35% increase in their yield and peak strengths, about 40% increase in the displacement ductility in the RC bridge columns. Additionally, the effect of loading cycle numbers on the seismic behavior of RC bridge column specimens is investigated. The effect of the number of loading cycles on seismic behavior is more significant after peak load than prior to the attainment of peak strength, and the deformation capacity is significantly reduced. During post-peak loading stage increasing the loading cycle numbers accelerates damage accumulation and impairs the seismic behavior of the specimens due to substantial reduction of their energy dissipation capacity and seismic ductility. Based on the analysis of test results under varied loading cycles and monotonic lateral force–displacement curves, a calculation model of lateral force–displacement relationship considering the influence of loading cycle numbers is developed, and its effectiveness and accuracy is verified. The objective of this paper is to investigate the effect of the number of loading cycles on the seismic behavior of RC bridge columns through experimental testing. The research results would improve seismic assessment of RC bridge columns exposed to such hazards that flexural-shear failure caused by cyclic degradation.