Seismic Performance of a Concrete Bridge Bent Consisting of Three Steel Shell Columns

This paper describes the performance of a full-scale, three-column concrete bridge bent test unit that was designed, constructed, and tested under simulated in- plane seismic loads. Representing a typical bent configuration used by the Alaska Department of Transportation and Public Facilities, the test unit employed 12.7-mm-thick steel shell concrete columns and evaluated adequacy of an improved beam-to-column joint design procedure. The steel shell served as the external reinforcement and formwork for the columns. As intended, plastic hinges were fully developed in the columns adjacent to the interface with the cap beam, with minimal damage occurring to the cap beam and joints due to simulated seismic actions. These observations, along with the recorded force-displacement hysteretic response, confirmed the desirable seismic performance of the test unit. Design details, analytical response, test observations, key experimental results, and design recommendations are presented.