The strength and reliability of aluminium stiffened panels

Abstract

The objective of this thesis is to develop improved reliability-based structural design methods for stiffened aluminium. panels in high-speed vessels. In recent years aluminium high-speed vessels have grown larger and are venturing into increasingly hostile operating environments. Designing such vessels requires structural prediction techniques capable of producing a light structure with high confidence in its strength and safety. However, current aluminium marine structural design methods are largely simple modifications of steel methods that do not account for all of the differences between aluminium and steel. TTds thesis presents new reliability-based design techniques for the ultimate strength and fatigue strength of aluminium stiffened panels. A review of recent aluminium high-speed vessels is made, along with their structural configuration and hydrodynamic loading. Structural reliability techniques are discussed. Existing prediction methods, including marine approaches and civil engineering design codes are compared to experimental results for the compressive collapse of aluminium plates and stiffened panels. A modified technique is proposed to model the compressive collapse of such panels. The tensile response of welded aluminium, structures is investigated, including the influence of strain concentration in the reduced-strength region around welds. Reliability formulations are presented and discussed for ultimate strength predictions. A reliability based hot-spot S-N fatigue prediction method is developed for welded connections, including an analysis of the material and prediction uncertainty values and a comparison with existing design codes. Discussion of extending the fatigue prediction techniques to include through-life initiationpropagation fatigue models are presented, along with a simple trial application to butt welds. Conclusions from the techniques investigated are presented, and potential future developments are discussed.