Experimental Investigation and Level Classification on the Postearthquake Vertical Load-Carrying Capacity of RC Columns

This study aims to reveal the failure mechanism and performance law of the vertical mechanical performance of earthquake-induced cumulative damaged RC columns and quantify the vertical load-carrying capacity (VLCC) thresholds under various damage states and residual drift ratios. To this end, five RC columns were constructed and tested, of which four RC columns were first subjected to the lateral cyclic loading tests to generate various cumulative damage and residual drift ratios and then the axial compressive loading was carried out to obtain their residual VLCCs. For comparison, the remaining RC column was directly tested under axial compressive loading to examine the original VLCC. The experimental results indicate that the damage level and the residual drift ratio significantly affect the residual VLCC of RC columns. In particular, the failure patterns of the damaged RC column under axial compressive loading mainly depend on its residual drift ratio. Excessive residual drift may result in the transformation from the shear-crushing failure to the flexural-overturning instability failure of cumulative damaged RC columns, resulting in the VLCC significant decrease. Then, the lognormal cumulative function was validated to describe the relationships between the damage level/residual drift ratio and the VLCC based on the experimental results. Subsequently, the optimal selection of the probability distribution of the loss ratio of VLCC (LVLCC) samples was carried out by utilizing the nonparametric tests, and the LVLCC thresholds were quantified for various damage states and the residual drift ratios. The LVLCC thresholds for various levels can provide critical references for the assessment of the postearthquake serviceability of the structures.