Seismic fragility evaluation of various mitigation strategies proposed for bridge piers

Abstract

Concrete bridge piers are vulnerable to strong ground motions because of inducing significant residual drifts, which reduce the seismic resilience of bridges. A broad range of mitigation techniques is presented in the literature to reduce the vulnerability of bridge piers located in high seismic zones. Hybrid reinforced concrete piers are the most popular techniques to improve the seismic resilience of highway bridges. In addition, posttensioned segmental bridge piers are proposed as an alternative to expedite the construction procedure and also meliorate the performance of bridges in terms of residual deformations. However, very limited studies investigated the seismic performance of a whole bridge, especially for the purpose of comparing seismic resilience of the bridge columns. In this paper, a comparative study is implemented to explore the seismic vulnerability of a bridge reinforced with a hybrid configuration (i.e. combination of shape memory alloys (SMA) and normal-strength bars, and combination of high-strength and normal-strength bars) as compared to a reference conventional pier, which fully reinforced by normal-strength rebars. Moreover, a posttensioned segmental pier is considered to evaluate the strength and self-centering ability of this pier as compared to the monolithic ones. To do so, a 2D bridge model is developed in OpenSees simulation platform. Fragility curves are developed to assess the seismic vulnerability of the bridge model constructed with different piers. In this regard, a suite of 20 near-fault earthquake motions are applied to the bridge through Incremental Dynamic Analysis (IDA). Each of these records is scaled to 15 Peak Ground Accelerations (PGAs) ranging from 0.1g to 1.5g. The fragility curves reveal the chance of failure for each bridge model and aid in determining the impact of each pier on the seismic vulnerability of the bridge.