Fully-plastic crack propagation in stiffened plates

The detachment of a stiffener from a plate is described by the fully-plastic crack propagation in the web of a non-symmetric I-beam. The lower flange of the non-symmetric I-beam represents the effective plate width, which may peel away from the stiffener. By assuming a rigid, linear strain-hardening material, we distinguish between two responses of the lower flange depending on the load amplitude: deformation without crack growth and deformation with crack growth. The bifurcation point that marks the transition from a deformation without crack growth to deformation with crack growth is independent of the initial crack length, but depends on the relative magnitude of plastic modulus to the material flow stress, the specific work of fracture, and the relative size of the tear zone and width of the flange. A parametric study shows that bifurcation load increases approximately linearly with an increasing ratio of web to flange widths for some chosen material constants. The effective width of the stiffened plate is thus an important parameter in the detachment of the plate from the stiffener.