A fragility-based framework for identification of unfavorable impact location for bridge columns under barge collisions

Abstract

The vessel-impact location on bridge columns varies with the water level of a river. For safety reasons, it is expected that the chosen impact location is the most unfavorable for vessel-impact-resistant designs or performance evaluations of bridge structures. However, neither the current design codes nor existing studies have explored this issue in depth. To this end, a fragility-based framework is proposed in this study to identify the most unfavorable location for bridge columns against barge collisions. In the proposed framework, an impact fragility analysis (IFA) process is employed to assess the failure probability of a bridge structure under barge collisions at different locations, in which different failure modes and the uncertainty of barge loads are considered. The multi-platform simulation models integrating VecTor2 and OpenSees are developed to properly compute the structural demand (e.g., shear distortion and mean curvature at key regions alone the pier) under barge collisions. A new intensity measure (IM), i.e., effective energy, is proposed for IFA to reflect the hazard level of barge collisions. The proposed framework is applied to a typical double-column bridge structure and the analysis results indicate that the stiffness and ductility of the column at the impact height play a significant role in structural damage. The most unfavorable impact location is approximately 1.5 times the column diameter from the column bottom, followed by the mid-point of the pier.