Improving Existing Inverted-T Bent Caps for Serviceability and Strength by Retrofitting with Supplemental Steel

Abstract

Undesirable cracking is commonly observed in existing bridge bents with inverted-T bent caps at the web-to-ledge interface. Although the cracking is unexpected, such cracks may decrease service life and are possible signs of structural deficiencies. In this study, concepts of retrofit solutions for improving the performance of such bent caps were developed and experimentally investigated. The solutions were designed to provide supplemental ledge and hanger load paths by attaching additional steel components: a post-tensioning (PT) threadbar with a “catcher” channel or end-region stiffeners. Experimental test results demonstrated the retrofitted inverted-T bent caps remained in a good (operational) condition to levels above the service limit state and had load carrying capacity up to 60% above the specified ultimate load demands. These experimental observations for both as-built and strengthened bent caps were compared to the calculated strength capacities, and the code-based strength capacities were shown to be overconservative. Repair and retrofit design recommendations are provided, including limitations, based on the experimental investigation.