A simplified crack model for weld fracture in steel moment connections

This paper presents a simplified two-dimensional crack model for assessing the fracture of bottom flange welds in steel beam-to-column connections. The formulation of the model includes the determination of approximate expressions for stress intensity factors related to the cracked geometry, accounting for typical stress conditions and taking due consideration of the presence of the backing bar. Idealized residual stress distributions are also incorporated in the model to examine their influence on the behaviour. Particular attention is given to typical connection configurations, which have suffered considerable damage in the Northridge earthquake. Comparisons are made between the results obtained from the proposed model and those available from a number of experimental investigations as well as two-dimensional finite element analyses. Within the range of results examined in this study, the proposed model is shown to provide good, and generally conservative, predictions in terms of both the fracture moments and reduction in stiffness.