Dynamic response of bridges to moving trains: A study on effects of random track irregularities and bridge skewness

This paper describes research undertaken to consider the dynamic responses of an existing railway bridge subjected to moving trains. The study investigated dynamic effects produced by different service trains, as well as the influence of random track irregularities and bridge skewness. This research was carried out using the dynamic bridge–train interaction (DBTI) model developed and previously verified by the authors. Generally, dynamic amplification of displacements was found to be moderate and compared favourably with recommendations of current design codes. The use of complex numerical models for bridge–train dynamics produced detailed dynamic responses; such results may be quite beneficial to bridge owners in the assessment of existing bridges which exhibit excessive dynamic responses. Random track irregularities were found to have minor effects on the dynamic amplification factors and bridge accelerations; however, lateral responses of the bridge were considerably affected by irregularities. Effects of irregularities were more pronounced in train responses; generally, the train responses increased with decreasing track profile quality. Bridge skewness was found to increase fundamental natural frequency of the bridge; this leads to a shift in the dynamic amplification factor towards higher speeds and alterations of its magnitude. Three-dimensional models were found necessary for accurate predicting of this response.