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This article presents a numerical study that aims to explore the dynamic behavior of railway bridges under vibrations induced by heavy-haul traffic. For this purpose, a finite element code that can conduct moving load and moving mass analysis of single span bridges was developed. The software was validated by comparing the numerical response to the analytical solution for various speeds. The numerical analysis of the benchmark bridge under the benchmark train showed the interplay between the natural frequency of the bridge, the mass of the train and the loading frequency. A comprehensive parametric study to investigate the impact of different parameters on the dynamic behavior of railway bridges is also provided. The bridge span length, normalized train length, normalized mass of the train, bridge deck stiffness, and train speed are the variables considered in the parametric study. The results of the extensive numerical analyses improve the understanding of railway bridge behavior under heavy-haul trains, and highlight the impact of the inertial effect of the trains on bridges, especially for varying span length and deck stiffness. It is also demonstrated that, when the train-to-bridge mass ratio exceeds 40%, the inertial effects of the train mass needs to be included in the analysis in order to obtain a reliable estimate of the bridge behavior under different train speeds. [ABSTRACT FROM AUTHOR]

This article presents a novel methodology to extract the bridge frequencies from the vibrations recorded on train-mounted sensors. Continuous wavelet transform is used to distinguish the bridge frequencies from the other peaks that are visible in the Fourier amplitude spectrum of the accelerations recorded on train bogies. The efficacy of the proposed method is demonstrated through numerical case studies. For this, a detailed three-dimensional finite element model that can capture the vibration characteristics of the bridge, track, and train is created, and each component of the model is separately validated. The train model used is a three-dimensional multi-degree-of-freedom system that can simulate the pitching and rolling behavior. The train was then virtually driven over the bridge at different speeds and under varying track irregularities to evaluate the robustness of the proposed method in extracting bridge frequencies from train-mounted sensors under different conditions. The proposed methodology is shown to be capable of identifying bridge modal frequencies even for aggressive track irregularity profiles and relatively high speeds of trains. [ABSTRACT FROM AUTHOR]

• Experimental campaign was conducted to evaluate the damping in masonry arch bridges under service loads. • Both ambient vibrations and vibrations under train loads were monitored and the damping values were extracted. • Damping ratios from ambient vibrations were shown to be unfit for use in dynamic analysis of masonry arch bridges under service loads. • Suitability of different viscous damping models in emulating damping behavior of masonry arch bridges was investigated. • The inherent nonlinear mechanisms in discrete-continuum models can be sufficient to capture the energy dissipation in masonry arch bridges under service loads. This article investigates the damping behavior of masonry arch bridges under service loads extracted from experimental data and provides guidelines on how to emulate this behavior in numerical analysis, particularly in discrete element model applications. First, an experimental campaign is undertaken and vibrations on three masonry arch railway bridges under train loads were monitored. The modal damping ratios from several sensors on each bridge were extracted by isolating the modal component of free decay vibrations which commence immediately after the train leaves the bridge. The modal damping ratios identified under service loads were compared with their counterparts identified under ambient vibrations. The suitability of mass-proportional, stiffness-proportional and Rayleigh damping models in emulating damping in masonry arch bridges was evaluated. In the numerical phase of the study, a single-arch masonry bridge was modeled using mixed discrete continuum approach and a moving load analysis was conducted without applying any additional viscous damping. The results of the numerical analysis indicate that the inherent damping in discrete element models provided by their nonlinear nature can be sufficient to emulate the damping behavior of masonry arch bridges under service loads. The research provided in this article is unique in the sense that it combines an experimental study and a numerical study on damping of masonry arch bridges under service loads. Unlike its counterparts in literature, which use either ambient vibrations or seismic action, damping values are computed under appropriate levels of vibration amplitudes for service loads, which is critical to estimate the modal damping ratios accurately under these loads. [ABSTRACT FROM AUTHOR]

A new framework for long-term monitoring of bridges is proposed in order to negate (i) the impact of measurement uncertainties on damage detection in vibration-based structural health monitoring and (ii) the low sensitivity of damage indicators to low levels of damage. The framework is developed using three vibration-based damage indicators that have an intuitive physical correlation with damage: modal curvature, modal strain energy and modal flexibility. The article first quantifies the efficacy of these damage indicators when based on two observations, one from the undamaged state and one from the monitored state, in detecting and locating damage for different damage levels that are simulated on an 84-m long railway bridge. A long-term monitoring framework based on a new parameter defined as the frequency of the damage indicator exceeding the threshold value within a population of observations is developed. Impact of several factors including the damage location, damage indicator used in the framework, and the noise level on the success of the developed framework was investigated through numerical analysis. The new parameter, when used together with modal strain energy, was shown to provide a very clear picture of damage initiation and development over time starting from very low damage levels. Furthermore, the location of the simulated damage can be identified successfully at all damage levels and even for very high noise levels using the proposed framework. [ABSTRACT FROM AUTHOR]