Fatigue behaviour of composite girders with composite dowels assuming randomly distributed input parameters

Nominated for Eurosteel 2021 Best Paper Award
The fatigue design of shear connectors for composite girders is based on fatigue strength curves (with 95 % survival probability) derived from tests with one or just a few connectors. According to the Eurocodes, the lifetime of a girder can then be limited by failure of the shear connector with the highest fatigue utilization. The failure probability of a component is thus determined by the failure probability of one shear stud or composite dowel, although a composite girder is an internally highly statically indeterminate system with the capability of redistributing forces in the composite joint. This paper outlines how considering crack propagation, the residual capacity of shear connectors with cracks and the redistribution of forces towards less stressed and damaged connectors can have positive effects on the lifetime of a girder. The failure probability of a girder is determined by several Monte Carlo simulations using a simplified FE lamella model with incremental calculation of the degradation of the connectors. The input parameters with the greatest influence on the fatigue behaviour of the girder are evaluated. Furthermore, the results show the economic potential of a future global safety concept for composite girders, especially those with composite dowels.