Longitudinal deformation of expansion joint of suspension bridge under wind and random traffic flow

To dynamically simulate and evaluate the longitudinal deformation performance of expansion joint of long-span steel truss suspension bridge under the combining action of wind and random traffic flow at operation stage, an analysis system of wind-random traffic flow-steel truss suspension bridge was established. Based on the existing wind-vehicle-bridge coupling vibration analysis system of single beam, the spring element was introduced to simulate the expansion joint, and the analysis system was improved from the single beam to the grillage method via two aspects of the vehicle-bridge coupling relationship and the fine loading of wind on steel truss girder section. The traffic flow load was simulated and reproduced based on the monitoring data. The dynamic displacement time history response of expansion joint of a typical long-span steel truss suspension bridge under the action of random traffic flow was calculated through the established analysis system. The correlation between the cumulative displacement and traffic flow weight was obtained and verified. Taking the thickness of wear-resisting material of sliding support as the evaluation indicator, the critical value of cumulative displacement of expansion joint was determined, and the normal service life of expansion joint was evaluated. The parameter sensitivity analysis on the longitudinal deformation performance of expansion joint under different wind speeds and random traffic flow was carried out. Analysis result shows that the hourly maximum displacement of expansion joint under the random traffic flow is far less than the designed allowance-880-880 mm. The cumulative displacement of expansion joint is positively correlated with the traffic flow load in corresponding period. Under the combining action of wind and random traffic flow, when the wind speed is less than 15 m·s^-1, the main load factor affecting the longitudinal deformation of expansion joint is random traffic flow load. When the wind speed is greater than 15 m·s^-1, the main load factor is wind load. Both the hourly maximum displacement and hourly cumulative displacement of expansion joint increase with the increase of wind speed. When the wind speed increases to 20 m·s^-1, the longitudinal deformation of expansion joint generated by the wind load is approximately 2 times of that under the traffic flow load. The established wind-random traffic flow-steel truss suspension bridge analysis system can provide a numerical analysis platform for dynamic simulation and performance evaluation on the longitudinal deformation of expansion joint under operation loads.