Shear Loading in Two-Column Bridge Bents

The seismic performance of two-column bridge bents was investigated by quasi-static testing two one-third-scale bridge bents replicating the Dumbarton Bridge in the San Francisco Bay Area. Both tall flexurally dominated and short shear-dominated specimens were represented. For both tests, experimental activity focused on lateral force distribution between the two columns and how the distribution relates to lateral capacity of the bents. A three-dimensional (3-D) finite element analysis computer model, validated by experimental results, was used to perform a parametric study of a variety of bent configurations to determine shear distribution between columns and to establish the specific column that governs shear design. Results showed that the column under compression was more vulnerable to shear degradation and, prior to first yield, the compression column resisted a larger portion of lateral force than the tension column in two-column bridge bents.