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A reliable evaluation of dynamic amplification effects is crucial in bridge design in order to achieve safer and economical solutions. In engineering practice, these effects are commonly taken into account through dynamic load allowance factors (IM) specified by the codes. However, some codes allow the calculation of these IM factors through more advanced dynamic analysis in order to achieve more realistic results. Therefore, a methodology to numerically evaluate the IM in bridges is described. The methodology is based on a vehicle-bridge interaction model that can take into account any configuration of pavement irregularities. A case study consisting of two modular steel bridges is presented. In order to reach a comprehensive characterization of the IM factors, a probabilistic analysis is conducted, taking into consideration the stochastic generation of random irregularity profiles based on pavement roughness and experimentally measured manufacturing imperfections, as well as a wide range of vehicle speeds. The results obtained in this study demonstrate the advantages of performing a probabilistic numerical evaluation of the IM factor in comparison to the use of pre-defined factors proposed by design codes. The consideration of IM factors based on probabilistic assessments can lead to relevant material savings in the design of steel modular bridges.

This article describes the simulation of the Korean high-speed train passing over a single-track viaduct and the influence of track isolated defects on the dynamic behaviour of the system. The model of the viaduct is validated and calibrated using a finite element model updating technique, and a three-dimensional (3D) model is used to account for the local deformations of the slab accurately. The direct method, an efficient vehicle-structure interaction algorithm previously developed by the authors, is used to solve the dynamic problem. It proved to be significantly more efficient than the widely used finite element software ANSYS® when solving large and complex problems. The computational time has been reduced by more than ten times. The results obtained show that the shape of the isolated defects and the local deformations of the slab strongly influence the dynamic behaviour of the system. Neither is taken into account in the current standards, and hence further research is necessary.

The present paper presents a methodology for evaluating the possibility of derailment of trains running over bridges subjected to crosswinds. The dynamic model consists of a train–bridge interaction coupling system that takes into account the contact interface between wheel and rail from which the contact forces arise. These contact forces are the inputs for the safety criteria that are later used to evaluate derailment. The wind fluctuating component is accurately considered through a stochastic process that generates correlated wind velocity fields, which are later converted into wind loads that are applied to both the bridge and the train. Before evaluating the running safety, the dynamic response of the train–bridge system is assessed to understand the influence of the train speed and wind velocity on it. Then, the running safety is analyzed based on three criteria, namely the Nadal, Prud’homme and unloading indexes, being the influence of the bridge lateral flexibility in the derailment risk also discussed. Finally, the results obtained with the stochastic wind model are compared with those obtained with a simplified discrete gust model proposed by the European normative. The maximum wind velocities, obtained through the stochastic and simplified formulations, for which no derailment criteria allowance is exceeded are computed and a comparative critical analysis between the models is presented.

This article presents an accurate, efficient and stable algorithm to analyze the nonlinear vertical\ud vehicle-structure interaction. The governing equilibrium equations of the vehicle and structure are\ud complemented with additional constraint equations that relate the displacements of the vehicle with the\ud corresponding displacements of the structure. These equations form a single system, with displacements\ud and contact forces as unknowns, that is solved using an optimized block factorization algorithm. Due to\ud the nonlinear nature of contact, an incremental formulation based on the Newton method is adopted. The\ud vehicles, track and structure are modeled using finite elements to take into account all the significant\ud deformations. The numerical example presented clearly demonstrates the accuracy and computational\ud efficiency of the proposed method.

Train running safety is a major concern among railway engineers, since a derailment may cause significant personal and material damages. This problem becomes more important if the derailment occurs on bridges, especially at high-speeds, where the consequences may be even worse. The sudden development of high-speed (HS) railway networks that occurred at the end of the 20th century and beginning of the 21st century demanded the construction of new lines with large curve radii in order to fulfill the design requirements of this type of transport. By adding this fact to the orography constraints and, in some cases, to constraints related with the lack of construction area and with the high costs of expropriation, several HS lines started to be developed with more than 75% of their length built over viaducts and bridges. Naturally, this relatively new reality led to a significant increase in the probability of a train being exposed to natural hazards that might jeopardize its stability when it is running over an elevated structure. Hence, this paper aims to present a comprehensive literature review of the problematic associated with the train running safety assessment on bridges. The existing normative criteria from different regions of the world related to this topic are summarized in a first stage. Then, the paper gives a brief description of the available train-bridge interaction models needed to explicitly assess the traffic stability, followed by a presentation of the running safety indexes used to assess the derailment risk. Finally, the available applications regarding the traffic stability against different sources of excitation are systematically reviewed and guidance to future research work on this topic is provided.