Dynamic response of railway bridges, Part II: Parametric and case studies on bridge-train dynamics and interaction

This paper describes the application of the DBTI model to a parametric study, as well as to analysis of three-dimensional response of an existing railway bridge; details of the model developments are described in the accompanying Part I paper. In the parametric study detailed in Part II, effects of the frequency and mass parameters on the dynamic response of the bridge were investigated. It was found that, for the practically applicable range of speed parameters, an increase in the frequency parameter increases the bridge response. The bridge-vehicle interaction was found insignificant only for low values of either speed or frequency parameters. Increasing the mass parameter was found to increase the dynamic amplification at low speed parameters, but to significantly reduce the amplification at higher speeds. Effects of the interaction on the dynamic response were found to be negligible for calculation of the dynamic amplification factor when either the mass or the speed parameter is low. The dynamic analysis of an existing railway bridge subjected to four different types of service trains was performed using the DBTI model. Generally, dynamic amplification of displacements was found to be moderate and compared favourably with that recommended by EN1991:2 [1]. It was also found that the use of complex models for bridge-train dynamics produces refined dynamic responses that could provide gains in situations where bridges assessed in a traditional manner fail the assessment criteria. The skewness of a bridge was found to increase its fundamental frequency, 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 prediction of this response.