Relationships of Barge Bow Force–Deformation for Bridge Design

Loads generated during vessel collisions with bridges are inherently dependent on force–deformation characteristics of the impacting vessel. Currently in the United States, barge impact forces used in bridge design are computed with a force–deformation (crush–curve) model proposed by AASHTO. A recent study uncovered important limitations in the AASHTO barge-crushing model, and a revised procedure for developing barge force–deformation relationships was developed. However, relationships developed in this previous study were based on the assumption that impact occurred directly head on to the impacted pier; the scenario was unlikely. Impact more likely occurs at some oblique angle. This paper shows that barge impact forces on flat-faced pier surfaces (i.e., rectangular columns or waterline pile caps) are typically less severe when collisions occur at even small oblique angles. Thus, the current study focused on updating the prior crushing model to account probabilistically for reduced forces associated with oblique impact. In this paper, oblique impact forces were quantified by means of a series of high-resolution simulations of finite element barge bow crushing. Results obtained from these simulations were used in a probabilistic study to develop a force prediction model that implicitly accounted for the relative likelihood of impact occurring at particular angles. Findings from the current study were then integrated into the previously developed barge-crushing model to produce a design-oriented calculation framework that would permit bridge designers to account easily for force reductions that arise in oblique impact scenarios.