Cumulative-impact method for the assessment of dynamic crush curve of crashworthy devices

Abstract

Crashworthy devices are integral for protecting bridges from vessel collisions, typically evaluated through finite-element methods. However, experimental verification is challenging owing to the impracticality of using large-scale, high-velocity vessels. In this study, a cumulative-impact method is proposed, which is theoretically and experimentally validated. It uses a small-scale impactor in multiple impacts to determine crashworthy device dynamic crush curve based on energy balance theory. The accuracy of the proposed method depends on the number of impacts and the impact velocity. The relative errors are < 5% for the peak impact force and residual deformation, if the number of impacts is < 5 and the impact velocity is > 3 m/s. A parametric study explores application conditions for the cumulative-impact method through horizontal-impact tests, indicating that small-scale multi-impacts and large-scale single impacts have consistent dynamic crush curves. The proposed method is sufficiently accurate to be used to determine the safety assessment of bridges under vessel collisions.