The objective of this paper is to assess the effect of ring stiffeners on the local response of cylindrical shells subjected to large deflections caused by transverse concentrated loads. A new model has been developed to account for the strengthening of the shell in the circumferential direction as the deformation zone spreads away from the load application point. The model is general and can be applied to shells with any type of stiffeners. Strains and rotations were also determined in the dent-affected zone near the stiffeners. It was found that ring stiffened shells are more susceptible to fracture than similar shells with uniform thickness.
The objective of this study is to extend the plastic analysis of local denting of unstiffened cylindrical shells developed by Wierzbicki and Sub (1987), to ring stiffened shells. Observations show that while the ring stiffeners increase the strength of the shell, they may cause premature fracture in the case of extreme loads. The fracture process is driven by the local stress and strain fields near the crack tip, and these local fields depends on the global deformations and forces in the structure. Therefore, it is important to formulate and analyze the global denting response of the stiffened shell. The present analysis can also be applied in damage assessment of offshore installations collided with supply boats or moving ice floes; hydrodynamic waves impact on tubular members; impact caused by accidentally dropped objects; and ice scouring of Arctic pipelines. There has been increasing concern in the area of collision and damage of these structures. The approach taken in this research is based on the methodology developed by Wierzbicki and Sub (1987), in which the problem of large plastic deformation of an unstiffened tube subjected to lateral concentrated load, axial force, and bending moment was analyzed.