A new methodology development for flood fragility curve derivation considering structural deterioration for bridges

Floods have been knownto be one of the main causes of bridge collapse. Contrary to earthquakes, flood events tend to occur repeatedly and more frequently in rainfall areas; flood-induced damage and collapse account for a significant portion of disasters in many countries. Nevertheless, in contrast to extensive research on the seismic fragility analysis for civil infrastructure, relatively littleattention has been devoted to the flood-related fragility. The presentstudy proposes a novel methodology for deriving flood fragility curves for bridges. Fragility curves are generally derived by means of structural reliability analysis, and structural failure modes are defined as excessive demands of the displacementductilityof a bridge under increased water pressure resulting fromdebris accumulationand structural deterioration, which are known to be the primary causes of bridge failures during flood events. Since these bridge failure modes need to be analyzed through sophisticated structural analysis, flood fragility curve derivation that would require repeated finite element analyses may take a long time. To calculate the probabilityof flood-induced failure of bridges efficiently, in the proposed framework, the first order reliability method (FORM) is employed for reducing the required number of finite element analyses. In addition, two software packages specialized for reliability analysis and finite element analysis, FERUM (Finite Element Reliability Using MATLAB)and ABAQUS, are coupled so that they can exchange their inputs and outputs during structural reliability analysis, and aPython-based interface for FERUM and ABAQUSis newly developed to effectively coordinate the fragility analysis. The proposed frameworkof flood fragility analysisis applied to an actual reinforcedconcrete bridge in South Korea to demonstrate the detailed procedure of theapproach.