In order to analyze the influence of the stiffness change of the long-span track bridge on running safety of the train, a bridge and train analysis model, based on Chongqing Egongyan track bridge, is established to simulate and evaluate the spatial coupling dynamic response of the wind–train–bridge system through stiffness change and to propose the reasonable stiffness limit range of the long-span track suspension bridge. The results show that the dynamic characteristics of the bridge are good, and the safety of train operation and ride comfort meet the requirements when the vertical stiffness is 1/300–1/500 and the lateral stiffness is 1/600–1/1200; the dynamic response of the bridge and the running safety of the train are significantly sensitive to the stiffness change of the bridge, especially when the wind speed is 25 m/s and the vertical stiffness is 1/300, at this time, the derailment coefficient and the wheel load reduction rate reach 0.72 and 0.54, respectively, which are close to the limit standard, indicating that there are some potential safety hazards in train operation.

Due to the alignment of track bridges directly affecting the safety and comfort of rail traffic operation, the alignment prediction of track bridges needs to be accurate. However, the structure of steel-concrete composite beam (SCCB) cable-stayed bridges is more complex, and the alignment prediction needs to be more accurate. To further improve the accuracy of alignment prediction for large-span SCCB track cable-stayed bridges, a method based on the response surface method (RSM) is proposed. In this paper, the Nanjimen Yangtze River Track Special Bridge was taken as a case for research. Considering the randomness of the influencing factors, the 95% confidence interval was obtained by using Monte Carlo (MC) sampling analysis, and the predicted values were within the confidence interval. The results show that the method integrates the confidence interval under each confidence level by simulating the long-term deformation of different years after bridge completion. The method could accurately predict the alignment of large-span SCCB track cable-stayed bridges, and thereby provide technical support for alignment control and ensure the safe and comfortable operation of rail transit.

No abstract

The dynamic simulation calculation of gas pipeline network is complicated. Usually, for each pipeline, energy conservation, mass conservation and momentum conservation are used to establish the non-linear equations[1-2]. For some complex pipeline network flow with multiple entries and outlets, the calculation is very slow, and cannot achieve real-time calculation. This study presents a new method for calculating the pressure between pipelines by assuming that the pipeline is a single vessel, calculating the flow rate between the pipelines by the pressure difference between the pipelines, and then using the flow rate as the intermediate coupling relationship to calculate pipe pressure. This method is simple, fast, with few boundary limitations, which can assist the design and operation verification of complex pipeline networks.