Ultimate Strength Analysis of Stiffened Plates with Initial Imperfections

The ultimate strength assessment of the hull girder is important in the perspective of full collapse of the ship's hull. Due to the inherent imperfections (intial deflections and welding induced residual stresses) which may arise in steel plating as a result of manufacturing, the strength of the plating is subjected to further degradation. This paper presents a methodology to analyze the ultimate strength of stiffened panels considering the effect of initial deflections. Ship plating representative of Oil tankers and Bulk carriers classed as per the IACS-Common Structural rules has been selected for the ultimate strength evaluation. A series of non linear finite element analyses have been carried out using commercial software. The results have been validated with results available in literature. The effects of consideration of initial imperfections (initial deflections) for the ultimate strength analysis are discussed. The present analyses may prove to be useful for developing a tool for ship designers to evaluate structural safety in a rational manner.