Enhancing Shear Strength of Capbeam–Column Joints in Existing Multicolumn Bent Bridges Using an Innovative Method

Abstract

Nonintegrated multicolumn bents are the common type of substructure in existing bridges. Among all possible seismic defects in their behavior, capbeam–column joint behavior has not properly been acknowledged so far. Although for other defects some retrofit methods are available, there are only a few methods proposed for improving the shear strength of these joints. The purpose of this research was to assess the cyclic response of such bents and suggest a practical retrofit method for improving joint behavior without significant damage. To this end, a ¼-scale two-column bent, representative of existing bridges built before 1990, was tested. Using test results, a passive retrofitting method based on the increasing shear strength of joints was developed. The performance of the proposed method was examined on a new specimen similar to the first one. The results show that, unlike the reference bent, which was damaged extensively in joint regions, the joints in the retrofitted specimen did not suffer any damage, and all plastic hinges were formed at both ends of the columns, the desirable failure mode followed by seismic codes.