Multilevel Performance Classifications of Tall RC Bridge Columns toward Postearthquake Rehabilitation Requirements

Abstract

This study aims at developing appropriate multilevel performance classification of tall RC bridge piers for seismic design. A new performance classification toward postearthquake rehabilitation requirements is presented. It considers damage states of the local environmental conditions and accessibility of the potentially damaged part. To reduce postearthquake rehabilitation requirements, higher performance levels allowing only minor and moderate damages are advised for tall bridge piers. Two RC columns with high aspect ratios were designed, fabricated, and tested under static cyclic loading, focusing primarily on minor and moderate damage states such as residual concrete cracking and onset of visible concrete crushing. The experimental results show that the zero-tip-displacement crack width measured after the column returned to zero tip displacement significantly underestimated residual-cracking damage, while the zero-lateral-force crack width can be taken as an approximate estimation for the residual cracking on the safe side. An improved model is proposed to evaluate the cracking behavior beyond steel yielding. In this model, the expected residual-crack width is expressed as a function of the maximum crack width. The results obtained using the model show good agreement with the experimental results. For the onset of concrete crushing, 24 cantilever test columns in total were analyzed, with aspect ratios equal to or greater than 3.0 and axial-load ratios ranging from 0.05 to 0.25. The results indicate that a higher aspect ratio and lower axial-load ratio lead to a higher drift ratio corresponding to the onset of visible concrete crushing.