Assessment the influences of initial imperfections on the hull girder ultimate strength of ships

Abstract

In the process of shipbuilding, many methods of processing, assembling, erection, and welding are applied to build the panels, blocks and ship hull. The above-mentioned factors cause the appearance of deformations and residual stresses on the hull structure with different levels and ranges. The assessment of the influence of these imperfections on the hull girder ultimate strength is a matter of great significance in order to assess the seaworthiness, thereby making recommendations to overcome and ensure the ship's safety and operation’s satisfaction. To determine the hull girder ultimate bending moment, an iterative method is used and improved to cover the deformation and residual stress parameters into the structural components. The double hull very large crude-oil tanker, 313,000 tons of deadweight, is used to calculate the value of the ultimate bending moment for two conditions of ship such as hogging and sagging. The results of the ultimate bending moment for the above two conditions under the influence of the imperfections are given and evaluated. Several conclusions have also been drawn in this paper.