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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 proposes a novel method, entitled Reference-based Component Scaling (RCS) method, for estimation of bridge mode shapes using vehicle scanning methods. The proposed method uses two instrumented vehicles to measure the accelerations on the bridge. While one vehicle remains stationary on a pre-determined location, the other one travels over the bridge with a constant speed both exciting the bridge and recording its response. The accelerations recorded on both vehicles are then processed using variational mode decomposition method and Hilbert transform to obtain their modal components. Leveraging its comprehensive framework that incorporates modal components derived from both vehicles, the RCS method effectively tackles the primary challenges encountered by vehicle scanning methods. These challenges include: i) shifting and shrinking effects of bridge damping on mode shapes, ii) distortions in modal components due to incomplete elimination of the roughness effect and iii) distortions in modal components caused by acceleration peaks during the vehicle´s transition from a rigid platform to the bridge. To this end, the RCS method addresses adverse effects of bridge damping without a priori knowledge of the modal damping ratios. To assess the accuracy of the proposed method, numerical analyses were carried out on three different bridges with different number of spans and boundary conditions. The effect of crucial parameters such as road roughness, bridge damping, uncertainties in measurements, and existing traffic on the accuracy of the proposed method was investigated. The results of the numerical study show that the RCS method stands alone in providing accurate estimates of mode shapes of bridges that are seated on elastic bearings, that have realistic damping ratios and relatively high road roughness profiles. • A novel vehicle scanning method to estimate the mode shapes of bridges is proposed. • The Reference-based Component Scaling (RCS) Method uses two instrumented vehicles to measure the response of the bridge. • Through the normalization process, the RCS method tackles the challenges that current drive-by methods cannot address. • The RCS method stands alone in providing accurate estimates of mode shapes of bridges on elastic bearings that have realistic damping ratios. [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]