Experimental evaluation of post-tensioned bridge bent under cyclic loads and comparison to hybrid bridge bents

Abstract

Experimental results for a re-centering bridge bent whose concrete columns were post-tensioned with unbonded high-strength steel bars are presented. The initial post-tensioning forces to achieve column re-centering were obtained using rigid body analogy. Steel collars were provided at the top and bottom ends of the columns for confinement. The column-to-footing interface contained a polyurethane layer inside the shear key to reduce column damage. For the initial post-tensioning forces implemented in the experiment, concrete damage was observed at the bottom of the columns. The post-tensioned (PT) bars remained elastic up to the design drift ratio of 2.0% and yielded at a 5.0% drift ratio; the column longitudinal mild steel bars yielded at a drift ratio of 6.0%. The performance of the post-tensioned bridge bent without any external energy dissipators (PT-Only bent) was compared with that of two similar hybrid bridge bents reinforced with external energy dissipators: the first incorporating tension-only stretch length anchors, and the second incorporating a buckling restrained brace. The two hybrid bents displayed excellent performance compared to the PT-Only bent in terms of strength, stiffness, and hysteretic energy dissipation; however, the PT-Only bent had a superior re-centering efficiency compared to the two hybrid bents.