Experiments and Numerical Analysis of a Seismically Resilient Bridge Bent with Stretch Length Anchors as Energy Dissipators

Abstract

The experimental performance and numerical analysis of a hybrid two-column bridge bent was examined to evaluate its ability to self-center and dissipate hysteretic energy during earthquakes. The experiment was conducted using quasi-static cyclic loads on a scaled specimen with posttensioning bars for self-centering and stretch length anchors for hysteretic energy dissipation. Posttensioning bars were used to connect the cap beam, columns, and footings without any mild steel reinforcing bars crossing the cap beam-to-column and column-to-footing interfaces. The number of posttensioning bars and initial posttensioning forces and the number of stretch length anchors were determined using mechanics and equivalent design of reinforced concrete columns. No yielding of posttensioning bars, mild steel reinforcing bars, or steel spirals was observed up to a 3.5% drift ratio; yielding occurred only in the stretch length anchors that are replaceable after an earthquake. Several stretch length anchors experienced tensile elongation, which exceeded their diameter. The residual drift of the hybrid bridge bent remained below 0.5% at the maximum applied 3.5% drift ratio without any visible damage to the concrete, steel collars, or steel chairs. A nonlinear numerical model was developed to represent the hysteretic response of the rocking bridge bent and was compared with the experimental results showing acceptable global and local response. The experiment and the nonlinear numerical model demonstrate that the bridge bent remains serviceable after significant drift cycles without any damage requiring repairs, which improves seismic resilience.