On Sensitivity of Time Step for Dynamic Analysis of Bridges under Moving Loads

TL;DR

This paper investigates how the choice of time step affects the accuracy of dynamic analysis of railway bridges under high-speed moving loads, proposing an equation to determine the optimal time step based on bridge and load parameters.

Contribution

It introduces a new equation for selecting the proper time step in dynamic bridge analysis considering load speed and span length, improving analysis accuracy.

Findings

Proper time step decreases with increasing vehicle speed.

Longer spans allow for larger time steps in analysis.

An equation for determining optimal time step is proposed.

Abstract

In the analysis of structures under dynamic loads, selection of a proper time step has a great influence to reach exact results. In this research determination of proper time step in dynamic analysis of railway bridges under high speed moving loads is considered. Dynamic responses of four simple span steel bridges with 10, 15, 20 and 25 meter length to moving trains with speed from 100 to 400 km/h and axle distances from 13 to 23 meter are calculated considering different time steps in analysis. The results indicate that by increase in moving speed of vehicle (increase in loading speed) the length of proper time step for dynamic analysis is reduced. In contrast by increase in 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.