Use of Mechanical Couplers in Concrete Columns

Abstract

This paper investigates the seismic performance of a two-column bridge bent with a primary focus on the mechanical couplers used to connect the reinforcement bars at the base of the columns. Previous research has focused on the need to properly account for at-yield and post-yield tensile behavior of these connections, but little has been done in the area of research into the use and detailing of these couplers subjected to the compressive forces in the region of plastic hinges. To study the behavior of the mechanical couplers in compression, a two-column bridge bent was tested at the University of California, San Diego. In the test, mechanical couplers were used to attach the longitudinal reinforcement bars at staggered heights in the plastic hinge zone at the base of the columns in a manner that was similar to a prototype. The results of the test indicated that current design practices are inadequate to properly develop the necessary compressive forces in the reinforcement bars in these types of connections. Moreover, while the couplers in the test performed adequately, the compression region of the column became unstable due to the buckling of the steel reinforcement around the location of the couplers. This paper describes a shortcoming of the current methodology, along with solutions to provide a plastic hinge capable of delivering additional ductility during seismic events.