Local plastic collapse conditions for a plate weakened by two closely spaced collinear cracks

•We develop a model for residual strength of a plate with two collinear cracks.•The model is based on the distributed dislocation technique for an edge dislocation.•The model investigates the plastic collapse of the ligament between collinear cracks.•An experimental technique is developed to validate the model.

Fracture assessment of structures weakened with multiple site damage (MSD), such as two or more interacting cracks, currently represents a challenging problem. Strength calculations of structural components with MSD are still largely based on two-dimensional solutions for single (or isolated) cracks available in various texts and handbooks or derived from a simplified finite element analysis. Such simplifications could often result in non-conservative predictions. Therefore, there is a strong motivation for the development of more advanced modelling approaches, which could incorporate effects of the interaction between multiple cracks, thickness-induced constraints and other nonlinear phenomena. The primary purpose of this work is to develop and validate a simplified three-dimensional analytical model for the evaluation of the residual strength of two through-the-thickness cracks in a plate of finite thickness subjected to uni-axial loading.