عنوان مقاله [English]
In the analysis of structures under dynamic loads, selection of a proper time step has great influence on reaching exact results. In this research, determination of the proper time step in the dynamic analysis of railway bridges under high speed moving loads is considered. Dynamic responses of four simple span steel bridges, with lengths of 10, 15, 20 and 25 meters, to moving trains with speeds from 100 to 400 km/h and axle distances from 13 to 23 meters, are calculated, considering different time steps in the analysis.The results indicate that increasing the moving speed of vehicles (increase in loading speed), reduces the length of the proper time step for dynamic analysis. In contrast, by increasing span length (increase in bridge vibration period), longer time steps can be used in dynamic analysis. In this research by investigation of dynamic analysis results, an equation is suggested for
determination of proper time step for dynamic analysis of bridges under moving loads.