Parametric Fragility Analysis of Steel Highway Bridges with Multi-Column Bents

초록

A fragility analysis includes the uncertainty of bridge properties such as material and structural properties. The material properties of concrete and reinforcement have a meaningful statistical characteristics, however, the gap size at expansion joints and the foundation rotational stiffness at footings vary so much from bridge to bridge that their mean and standard deviation do not have any meaning statistically. Therefore, this study considers the material properties of concrete and reinforcement as random variables, however, the gaps and the foundation stiffness are dealt with as varied parameters. The goal of this study is to assess the effect of the two bridge-parameters on the seismic fragility of the bridges. Additionally, this study suggested a combining method of fragility curves for bridge-components into a fragility curve for a bridge system and optimum parameters for bridges were determined through bridges' combined fragility curves. The target bridges in this study are multiple-span-simply-supported (MSSS) and multiple-span-continuous (MSC) bridge, which have multi-column bents and pier-deck-bearing connection, typically found in the Central and Southeastern United States (CSUS). Two retrofit measures, restrainer cables and lead-rubber bearings, are introduced and the effect of the two parameters on the retrofitted bridges is also assessed.

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