Seismic Analysis of Posttensioned and Hybrid Bridge Bents with Buckling Restrained Braces

Abstract

A numerical model is presented for a rocking bridge bent specimen consisting of two precast concrete columns with posttensioning (PT) bars, two footings, and a cap beam, with or without a buckling restrained brace (BRB). First, a numerical model of the posttensioned bridge bent specimen without a BRB is developed; emphasis is placed on modeling the rocking mechanism at the joint between precast concrete members joined only through PT bars. The numerical model is extended to a hybrid specimen consisting of a two-column posttensioned bridge bent with a BRB as an external energy dissipation device. Experimental results obtained from quasi-static cyclic tests of the posttensioned and hybrid specimens are compared with the numerical models. Satisfactory agreement of the numerical models with the experimental results is observed in terms of structural response, hysteretic energy, and PT-bar forces. The numerical models are subsequently extended to a previously tested three-column bridge bent for two configurations: (1) a posttensioned bridge bent with PT bars, and (2) a hybrid bridge bent with PT bars and two BRBs. A fiber-based bridge bent model is built, which includes soil–structure interaction (SSI) using simplified springs. A comparison of the posttensioned and hybrid bridge bents using far-field and near-field ground motions shows that the hybrid bridge bent displays superior performance compared with the posttensioned-only bridge bent.