Development of guidelines for transverse web frame design in polar class ships using non-linear finite element analysis

Abstract

This thesis aims to fill in the gaps that exist for transverse web frame design in polar class ships. The International Association of Classification Societies (IACS) has developed a set of harmonized rules that govern the design and construction of many different types of vessels. Traditional ship design used an elastic design point whereas the new Polar Class rules use a plastic design point. For polar class ships an agreement could not be reached within IACS governing bodies with regards to transverse web frame design. As no agreement was reached each classification society has adopted their own methods for the design and construction of transverse web frames. Many of the classification societies have adapted their rules from traditional steel vessel designs until an agreement can be made within IACS. The problem with this (aside from there not being harmonized rules across the classification societies) is that the design point for web frames using traditional steel vessel rules is elastic, while the design point of all the surrounding is plastic. This causes a mismatch in design philosophies where the web frames must be overly large in order to remain elastic under the design load. This thesis looks at the plastic behaviour of transverse web frames in two different polar class ships, at the design load and in overload scenarios, using non-linear finite element analysis and a “design of experiments” statistical approach. This thesis presents guidance on how to develop accurate finite element models for polar class ships and provides guidance on appropriate acceptance criteria for the plastic design/behaviour of transverse web frames.