Analysis of Fatigue Crack Propagation in Steel I-Beams with Welded Transverse Stiffeners Subjected to In-Plane Loadings

Abstract

For bridge structures, the fatigue crack propagation represents the mechanical damage that shortens the service life of the structures. Most fatigue cracks initiate at the welded details due to geometric discontinuities, residual stresses, and initial weld defects. The welded transverse stiffeners have been widely used to increase shear strength of the steel girders. Under cyclic in-plane loadings, however, the fatigue crack initiates at the end of the stiffener, i.e., in the web gap, and propagates into the girder web. The objectives of this study are to (1) numerically simulate the fatigue crack propagation in steel I-girders with welded transverse stiffeners and (2) study the effects of initial crack size, fillet weld size, stiffener dimension, and web-gap length on the fatigue crack propagation. The FRANC3D software was used to perform the analysis of stress intensity factor, crack propagation, and fatigue life. The numerical results showed that the fatigue life increases as the web-gap length increases, while it decreases as initial crack size and thickness of the transverse stiffener increase. Also, the stress intensity factors of the steel I-beams that include the fillet weld in the finite element models are slightly lower than ones modelled without fillet weld.