Retrofit Analysis of Bridge Fender Systems

Abstract

Several accidents in which vessels impacted bridges have led to significant improvement of design procedures for impact protection of bridge piers. However, the guidelines usually call for such expensive solutions as piers that can withstand a design force derived from local waterway standards. This paper presents an idea for retrofitting a certain class of existing bridge fenders to serve more efficiently as protective structures against such impacts. Computational analysis was conducted using the nonlinear, dynamic computer code LS-DYNA. The research concentrated on analysis of a collision of a Jumbo Hopper barge with a bridge fender consisting of concrete piles. Several impact scenarios were considered, and four different retrofit solutions were compared with the original design. The analyses performed were used to assess the crashworthiness performance of the fender system, and specific retrofit recommendations, allowing for more efficient kinetic energy absorption, were developed and compared with the original design. The numerical results from 3D computational mechanics were also compared and interpreted using a simple special-case, two-body analytical approach.