Fatigue assessment of a composite railway bridge for high speed trains. Part II: Conditions for which a dynamic analysis is needed

This paper is a continuation of the paper titled “Fatigue assessment of a composite railway bridge for high speed trains-Part I: modeling and fatigue critical details” with the emphasis on conditions for which a dynamic analysis is needed for a fatigue assessment of the bridge. In part I, a fatigue assessment of the Sesia viaduct is performed by using both a static analysis and a dynamic analysis with a moving load model; fatigue damage levels of several concerned details are calculated and the fatigue critical details are identified. It is found that dynamic effects induced by the high speed trains reveal a big influence on the fatigue damage of the bridge. In this paper, conditions under which a dynamic analysis should be considered for the fatigue assessment of a bridge are investigated. Three different alternatives are considered: a static analysis taken into account a dynamic amplification factor, a dynamic analysis with a moving load model, or a dynamic analysis with multi-body models for the train vehicles include the train–bridge interaction effect. The effect of several parameters related to the train and the bridge is studied. The train speed and the mass ratio between the train and the bridge are identified as significant factors that determine the dynamic effect on the fatigue damage of the bridge.