Deformations of high-speed railways accumulate over time and affect the geometry of the track, thus affecting the running safety of trains. This article proposes a new method to map the relationship between dynamic responses of high-speed trains and additional bridge deformations. A train–track–bridge coupled model is established to determine relationship between the dynamic responses (e.g. accelerations and wheel–rail forces) of the high-speed trains and the track deformations caused by bridge pier settlement, girder end rotation, and girder camber. The dynamic responses are correlated with the track deformation. The mapping relationship between bridge deformations and running safety of trains is determined. To satisfy the requirements of safety and riding comfort, the suggested upper thresholds of pier settlement, girder end rotation, and girder camber are 22.6 mm, 0.92‰ rad, and 17.2 mm, respectively. This study provides a method that is convenient for engineers in evaluation and maintenance of high-speed railway bridges.

Complex bridges will inevitably have cracks in operation. Dynamic characteristics with crack structures have been researched central issues. In the past, few researches were conducted from the whole structure of bridges with multi-cracks. In the meanwhile, related experimental research and systematic numerical simulation were lacking. In addition, researches on cracks seldom considered the high-order vibration characteristics of structures with multi-cracks. Aimed at this problem, this paper selected the whole bridge structure which was widely applied in engineering to study dynamic characteristics. For the concrete steel bridge with two cracks, this paper established finite element models for concrete steel beam and bridge with cracks under three different conditions and obtained vibration frequency and three order modes through simulation. Then, this paper analyzed and verified the correctness of numerical simulation result through experiment. Based on the verified model, this paper conducted a systematic analysis and summary, and obtained the following findings: The vibration frequency of concrete steel beams with cracks was obviously affected by cracks. The higher the order was, the greater the impact of cracks on frequency would be and the smaller the impact of cracks on the amplitude of modes would be. With the increased crack depth, the impact on the vibration frequency of concrete steel beams was more obvious. Additionally, crack distance also had some impacts on the dynamic characteristics of concrete steel beams. Numerical simulation model and method in this paper provided foundation and reference for continuing to analyze concrete steel beams with other crack forms or other structural forms. In the meanwhile, the three-dimensional analytical contour in this paper could help engineers to more intuitively understand and valuably apply the change rule of impact of crack depth and position on concrete steel beams.

With the development of the railway network in a harsh environment, the additional bridge deformations accumulated over time may endanger high-speed trains passing through a bridge, since the bridge deformation directly affect the geometry of the track on the bridge, thus affecting the dynamic responses of the train. This paper investigates the effects of different types of bridge deformation on the dynamic responses of the high-speed train passing through a deformed bridge. First, a finite element model is established for a high-speed railway bridge to study the dynamic responses of vehicle-track-bridge system under bridge deformations. Then, the rail deformation caused by bridge deformation is calculated using a bridge-track deformation mapping model, and used as the excitation to the vehicle-track-bridge system to study the influence of bridge deformations on the dynamic responses of the train. Results show that the vertical bridge deformations mainly affect the vertical vehicle dynamic indices, and have negligible effect on the lateral dynamic indices. The additional bridge deformation generates an additional low-frequency excitation to the train. The bridge deformations mainly affect the dynamic responses at specific characteristic frequencies, which are independent on the magnitude of the deformation. The frequencies for bridge deformations are magnified at about 1 Hz, indicating that the additional bridge deformation may aggravate the vertical vibration of the train.

In this study, a dynamic response analysis procedure is proposed and applied to investigate the dynamic responses of a straddle-type concrete-filled steel tube tied arch bridge under train and truck loadings. A numerical model of the coupled monorail train–bridge system is established to investigate the dynamic behaviors of the bridge under moving trains. A refined three-dimensional finite element model is built for the bridge and a 15 degrees-of-freedom vehicle model is presented for the train. The numerical model is validated using in-situ test results and then used to analyze the dynamic displacement and acceleration of the bridge and the trains on the bridge. Based on the simulation results, the impact factor of the bridge is investigated and the riding comfort of the trains is evaluated. The investigation results show that the impact factor of vehicle loads reaches the maximum value when the resonance of the bridge is induced by the moving vehicles. The effect of train braking predominates the longitudinal vibration of the bridge but is negligible in the transverse and vertical directions. The vehicle speed is the dominating factor for the riding comfort of the train.

In this study, the dynamic behavior of a concrete-filled steel tube (CFST) hybrid framed arch railway bridge under moving trains are investigated through an in-site dynamic test. The bridge was tested under train loadings in different scenarios and at different speeds of the trains. The free vibration characteristics, strain, displacement, and acceleration of the bridge structure were measured to evaluate the dynamic responses of the train-bridge coupling system. A three-dimensional finite element model, which took into account the train-bridge coupling and track irregularities, was established to analyze the behaviors of the train-bridge system. The model was validated against the in situ test results. The impact effect on the girder was greater than that of the arch frame. The acceleration responses of the trains on the bridge increased with the train’s speed. The riding comfort of the trains was evaluated based on the measured dynamic responses of trains.