Train-track-bridge dynamic interaction is a fundamental concern in the field of railway engineering, which plays an extremely important role in the optimal design of railway bridges, especially in high-speed railways and heavy-haul railways. This paper systematically presents a state-of-the-art review of train-track-bridge dynamic interaction. The evolution process of train-bridge dynamic interaction model is described briefly, from the simplest moving constant force model to the sophisticated train-track-bridge dynamic interaction model (TTBDIM). The modelling methodology of the key elements in the TTBDIM is systematically reviewed, including the train, the track, the bridge, the wheel-rail contact, the track-bridge interaction, the system excitation and the solution algorithm. The significance of detailed track modelling in the whole system is highlighted. The experimental research and filed test focusing on modelling validation, safety assessment and long-term performance investigation of the train-track-bridge system are briefly presented. The practical applications of train-track-bridge dynamic interaction theory are comprehensively discussed in terms of the system dynamic performance evaluation, the system safety assessment and train-induced environmental vibration and noise prediction. The guidance is provided on further improvement of the train-track-bridge dynamic interaction model and the challenging research topics in the future. ARTICLE HISTORY

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It is essential to establish a dynamic model of flexible multi-link mechanism with clearance and lubrication for ultra-precision presses to analyze its dynamic response. Traditional dynamic models of mechanical system rarely consider the effect of flexibility, revolute and spherical clearance joints, and lubrication together, which causes lower precision analysis. In order to study the dynamic characteristics of multi-link mechanism more accurately, a novel dynamic model of flexible multi-link mechanism with clearance and lubrication for ultra-precision presses is established in the present work, which considers the effect of revolute and spherical clearance joints, lubrication, and flexibility of crank shaft and linkage. It is demonstrated that the dynamic responses of flexible multi-link mechanism with lubricated clearance joint model agree better with experimental data than those with dry clearance model and the validity of the proposed model is verified. The simulation results also show that the existence of lubrication reduces the dynamic responses of flexible multi-link mechanism with revolute and spherical clearance in a significant manner and act as a suspension for multi-link mechanism.

This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.

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Railway-induced vibrations at low frequencies have become an important environmental issue with the rapid development of urban rail transit. In this study, a new vibration attenuation track (VAT) capable of passively mitigating vibrations at low frequencies is developed based on an integrated theoretical and experimental study. The full-scale VAT is built which incorporates a floating slab track (FST) and the attached dynamic vibration absorbers (DVAs) with key parameters determined by the fixed-point theory and modal analysis technique. The vibration attenuation performance of the VAT is investigated under train dynamic loads by establishing a three-dimensional coupled dynamic model of a metro vehicle-VAT-subgrade system, and is further elucidated and validated by carrying out full-scale dynamic tests under different harmonic loadings. Computational and experimental results both show that vibrations of the track are effectively absorbed by the attached DVAs leading to a significant reduction of the subgrade vibrations at the low frequency of 9-16 Hz. C 2017 Computer-Aided Civil and Infrastructure Engineering.

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