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, a refined finite element model was built that represented the structural and mechanical properties of railway bridges. A coupled vehicle-bridge vibration model was established to simulate the dynamic behavior of the bridge under moving trains. Field tests were then conducted to determine the free vibration characteristics as well as the strain, displacement, and acceleration of the bridge structure under trains moving at different speeds and braking at a specified position from a set speed. The dynamic response of the bridge was found to increase with the train speed, but the main beam of the bridge was more affected by a train braking than the one passing over it. Both the bridge and vehicle were found to meet the relevant requirements for safe design and operation, with the train exhibiting good running safety and smoothness, and the bridge structure showing sufficient stiffness and dynamic performance. Based on the field measurements and analytical modeling, it can be concluded that the use of appropriate equipment and the selection of a suitable layout for the sensors permit the assessment of the dynamic behavior of the bridges from vibration measurements. This indicates the potential for the continuous health monitoring of the railway bridges that may be sensitive to the vehicle-bridge interaction.
Studies on impact effects of trains on the railway bridge are important for ensuring the reliability of bridge and the safety of train operation. This paper presents an experimental study on the dynamic effects of moving trains on a long-span railway continuous beam bridge. The dynamic responses of the bridge under the moving trains were measured through in-situ testing and finite element analysis. The influences of the moving trains and track irregularity are considered. The investigated influencing factors include the weight and speed of the train and the irregularity of the track on the bridge. The results indicate that the train's speed does not have obvious influence on the impact factor, while train's weight and track irregularity have notable effects on the impact factor. But from the overall development law, with the increase of train speed, the impact factor increases. The impact factors obtained in this study are larger than the values provided by the China bridge design codes, which indicates that the bridge code underestimates the impact effect of the train on the bridge. The design value of the impact factor should be properly improved in the bridge design.
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