Calculation of dynamic stress intensity factors for cracked bridges under moving train load

Abstract

Accurate determination of the stress intensity factors for cracked bridges is crucial for their fracture and fatigue analysis. This paper proposes a generalized approach for the dynamic stress intensity factor calculation of cracked bridges subjected to moving train load. Dynamic equation of the cracked bridge is established by the extended finite element method, based on which 3D train-bridge coupled system model is formulated to characterize dynamic interactions between the train and cracked bridge and to yield near-tip displacement and stress fields. The interaction integrals of dynamic stress intensity factors for 3D railway bridge cracks are analytically deduced and numerically evaluated in conjunction with the extended finite element method for the first time. Three benchmark examples are subsequently used to verify the effectiveness of the developed computational procedure. Additionally, the proposed approach is illustrated on a cracked prestressed-concrete girder bridge in heavy-haul railway and the influence of key parameters on dynamic stress intensity factors is investigated. In the present work, two categories of dynamic effects in the determination of dynamic stress intensity factors are identified and quantified, which refer to coupled vibrations between the train and cracked bridge and inertial effects in the near-tip region, respectively. Capable of considering the above-mentioned dynamic effects, track irregularities, and prestress levels, among others, the proposed approach can be employed to accurately calculate dynamic stress intensity factors for 3D cracks in a variety of railway bridges under moving train load.