Analytical Modelling of the Inelastic Structural Response of RC Bridge Piers Under Train Impact

Abstract

The analysis of impact-related hazards for the design of bridge components in railway perimeters often receives insufficient attention. Code-based design procedures typically depend on equivalent static loads based on basic energy conservation laws ignoring the structural response. This study aims to identify the characteristics of the dynamic behaviour of both the impacting train and the impacted structure and the most influential parameters for assessing structural safety.The methodology consists of simplifying the complex three-dimensional structure to an equivalent single-degree-of-freedom (SDOF) system, considering the local dynamic behaviour of piers and their interaction with the global frame structure. The impacting train is modelled analytically as an inelastic mass-spring system, allowing the decoupling of the impact load and the structural response instead of modelling a 2-DOF system. The results obtained from this analytical approach are compared to numerical simulations based on a nonlinear finite element (FE) model, examining the structural behaviour under dynamic loading.Based on the findings from the theoretical and numerical investigations, a simplified design procedure for estimating the deformation demand and capacity of RC bridge piers under train impact is proposed. For the structures selected as examples, it is possible to predict the structural response with reasonable accuracy, eventually showing that not only the structural resistance should be considered but that the deformation capacity is of paramount importance.