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This paper presents findings on the effects of varying axial load on the seismic performance of reinforced concrete (RC) short columns that failed in shear by conducting an experimental program on five full-scale RC columns. The key variable of this paper is the applied axial load pattern. The seismic behavior of the columns subjected to varying axial load was experimentally appraised with regards to crack patterns, shear failure modes, hysteretic response, shear behavior, and drift and energy dissipation capacities. The test results indicated that the lateral load-displacement hysteresis loops of RC columns with varying axial load are unsymmetrical. Under varying axial load, the columns exhibited a very diverse seismic performance when compared to those subjected to constant axial load. Different shear failure modes were also detected between columns under constant and varying axial loads. The shear strength and its deterioration of columns strongly depend on both the fluctuating range and intensity of applied axial load. To supplement the experimental results, a three-dimensional (3-D) finite element (FE) model is proposed to further investigate the effects of varying axial load on seismic behavior of RC short columns subjected to varying axial force. The intensity and fluctuation of the applied axial load is found to have a significant effect on the shear strength of RC short columns. Comparisons with the current available model for assessment of shear capacity revealed that the ASCE/SEI 41-17 provisions tend to overestimate the shear capacity of RC columns subjected to varying axial load tested in this study. Therefore, a modification parameter is proposed when adopting the ASCE/SEI 41-17 provision to evaluate the shear capacity of RC columns under varying axial load. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study carried out on eight full-scale uncorroded and corroded reinforced concrete columns that were subjected to simulated seismic loading to investigate the effects of reinforcement corrosion on the seismic behavior of columns that failed in flexure. The main variables are the corrosion levels of reinforcement and applied axial force ratios. The seismic performance of test specimens was assessed in terms of crack pattern, hysteretic response, yield displacement, lateral load resistance, drift capacity, displacement ductility, and energy dissipation capacity. The results highlighted that the corroded columns suffered a significant degradation of strength and lateral drift capacity as compared to uncorroded columns. In addition, it is noteworthy to observe that the failure mode of corroded columns switched from flexural failure to flexural-shear failure and sudden axial failure when they are highly corroded and subjected to high axial force. An empirical equation based on the maximum pit depth of corroded longitudinal reinforcing bars was proposed to predict the residual flexural strength of corroded columns. Furthermore, based on the shear strength model proposed in ASCE/SEI 41-13, methods were proposed to estimate the shear strength of corroded columns failed in flexural-shear failure and axial failure, which consider the contribution reductions to shear strength of transverse reinforcement and concrete due to corrosion. Among these methods, the shear strength of corroded columns estimated based on the corrosion mass loss and average residual cross-sectional area was not conservative as compared to the test results. In contrast, the shear strength of corroded columns predicted using the minimum residual cross-sectional area of transverse reinforcing bars showed good and reliable correlation with the experimental results. [ABSTRACT FROM AUTHOR]