The main aim of this study was to investigate key parameters governing the dynamic response of bridge-train systems and to assess the significance of the bridge-train interaction in relation to these parameters. This study expands the previous work of Majka and Hartnett [2] to include various indicators of the dynamic response and the way they influence the bridge-train interaction. It is also the aim of this paper to provide general criteria when the interaction can be neglected without introducing significant errors into the dynamic response. This is of considerable practical importance and should allow for simplifying and speeding-up the dynamic analysis when those criteria are satisfied.

A number of factors were considered that included speed, as well as frequency and mass parameters. The dynamic response of bridge-train systems was comprehensively analysed by means of displacement-based and strain-based dynamic amplification factors, as well as bridge accelerations. The significance of the bridge-train interaction was assessed for each of these response indicators. This represents progress in comparison with previous studies where normally, no more than two-types of response indicators were used to investigate the bridge-train dynamics. The dynamic response of the bridge-vehicle system was found to be sensitive to the type of the load model used in the analysis and, particularly for high speeds, tended to be the greatest for the moving mass model, followed by the moving force and the moving system models. For lower speed parameters, different load models dominated the response, depending on the speed parameter. It was confirmed that when the frequency parameter is low, the response is very similar to that produced by the MF load model, i.e. little influenced by the interaction. Also, the level of the bridge-train interaction was found to vary significantly with the speed parameter.

Influence of the bridge-vehicle interaction on dynamic amplification of displacements was found insignificant when the speed parameter or the frequency parameter is low. Amplification of strains was found to be more sensitive to the interaction, however, the same criteria were found to be applicable here. Generally, the interaction should not be neglected where an accurate estimation of bridge accelerations is of interest. The effects of the interaction on the dynamic response were found to be negligible for the calculation of dynamic amplification factors when the mass parameter is low. Bridge accelerations were found to be much more sensitive to the interaction and it should be taken into account if accurate calculation of accelerations is required.

1

M. Majka, M. Hartnett, "Effects of speed, load and damping on the dynamic response of railway bridges and vehicles", Computers & Structures, 86(6): 556-572, 2008. doi:10.1016/j.compstruc.2007.05.002

2

M. Majka, M. Hartnett, "Dynamic Response of Railway Bridges, Part II: Parametric and Case Studies on Bridge-Train Dynamics and Interaction", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 191, 2007. doi:10.4203/ccp.86.191

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