Research on Refined Girder-End Displacement Calculation for Long-Span Railway Bridge

Girder-end expansion devices are critical to the running safety of trains on the long-span railway bridges as well as the service performance of the bridges. In this paper, refined calculations were conducted to investigate the girder-end displacements induced by thermal loads, train loads, wind loads, and combined wind and thermal loads, on the basis of the data of measured girder-end displacements and structural calculations of multiple long-span bridges. The types and ranges of thermal loads are suggested. The loading cases and methods to calculate the girder-end displacements induced by train loads are determined. The values of friction cocfficients of wind loads for trusses as well as the loading cases selected to calculate the girder-end displacements induced by wind loads are provided. The wind load reduction factors related to the combination of wind and thermal loads are calculated in the wind load model and the unified distribution model of wind and thermal loads. The proposed method has been applied to calculate the girder-end displacements of a cable-stayed bridge, and compared with the calculation efficiency of the conventional methods. It is concluded that the girder-end displacement induced by thermal loads is highly associated with the system temperature, during the fall of the system temperature, the temperatures of structurcs draw the values of atmospheric temperatures, while during the risc of the system temperature, heat radiation effect should be considered for the stay cables and half of the superstructure, and the temperatures of the pylons and the other half of the superstructure draw the values of atmospheric temperatures. The boundary resistance effects of the dampers and hearings should be considered, the dynamic time history method was used to calculate the girder-end displacements induced by train loads, the calculated results agreed well with the measured values. For the truss bridge, the girder-end displacements induced by wind loads calculated at wind yaw angles of 45° and 90°, and the most unfavorable values were selected. When calculating the girder-end displacement combinations under the action of wind and thermal loads, the displacements induced by wind loads should be discounted. The girdcr-end displacements calculated by the conventional methods were conservative, it is a better option to select the girder-end displacements via refined calculation. © 2024 Wuhan Bridge Media Co., Ltd., MBEC. All rights reserved.