Multiscale fatigue damage evolution in orthotropic steel deck of cable-stayed bridges

This paper investigates multiscale fatigue damage evolution in deck-to-rib (DTR) joints of orthotropic steel deck (OSD) of a long-span cable-stayed steel bridge under traffic loading with consideration of micro short crack nucleation and growth as well as macro long crack propagation. Multiscale finite element modelling and substructure techniques are jointly used to model a long-span cable-stayed bridge and simulate multiscale fatigue damage evolution in DTR joints. The polycrystal microstructure together with the crystal plastic constitutive model are used to model the fine-grained heat-affected zone of a DTR, in which micro short crack nucleation and growth are simulated considering the randomness of grain size and orientation. The polycrystal microstructure is embedded in a substructure while the substructure is coupled with the multiscale model of the bridge under traffic loading. After the micro short crack in the microstructure grows up to an initial long crack length, threedimensional macro long crack propagation is simulated in the substructure including the effect of mixed crack modes by fracture mechanics. As a case study, the multiscale fatigue damage evolution in the DTR of the OSD of the Stonecutters cable-stayed bridge in Hong Kong under moving vehicles is simulated using the proposed method. The simulation results indicate that the proposed multiscale fatigue damage evolution model can describe the entire damage process from micro crack nucleation to macro crack propagation. The case study shows that the macro crack propagates rapidly from the initial macro crack and the period of micro short crack nucleation and growth is longer than the macro crack propagation period.