The effect of slamming and whipping on the fatigue life of a high-speed catamaran

Abstract

In order to optimise the structural design of lightweight high-speed vessels, knowledge is required of the effect of sea loads on their structures, with respect to both ultimate strength and fatigue life. This paper reports on an investigation into the influence of slamming and whipping on the fatigue life of a large high-speed catamaran. Full-scale measurements of slam events were conducted on a 98m Incat catamaran to investigate its slamming behaviour in a variety of sea conditions. The full scale results were then used to determine the influence of the presence of slam events on fatigue life. In addition, the effects of significant wave height, slam occurrence rates, slam peak stresses and whipping behaviour on fatigue life were examined. The fatigue life was found to reduce significantly with the presence of slam events. Therefore, a reduction in slamming may prolong the fatigue life of a vessel markedly. The fatigue life was found to reduce significantly as wave height increases, as slam rate increases and slam peak stress increases. However, small slam events were found to have little or no influence on fatigue life. Whipping behaviour, in particular decay coefficient, may also strongly influence fatigue life.

Keywords:

• Fast ships
• wave slam
• whipping
• fatigue

Additional information

Notes on contributors

Giles Thomas

Giles Thomas is a lecturer at the Australian Maritime College. He received his PhD in 2003 from the University of Tasmania for his work on the slamming of large high speed catamarans. He is currently a chief investigator on a collaborative project with Incat and Revolution Design investigating asymmetric and non-linear loads on high-speed catamarans.

Michael R Davis

Michael Davis is a member of academic staff at the School of Engineering at the University ofTasmania. Formerly he has been President of the Tasmania Division of the Institution of Engineers, Australia, Chair of the College of Mechanical Engineers and Chair of the Tasmania Branch of and a member of the Australian Council of Professions.

Michael completed his bachelors degree in aeronautics and doctorate in sound and vibration at the University of Southampton. He subsequently worked at the de Havilland Aircraft Company and the Royal Aircraft Establishment, Farnborough before joining academic staff in the Department of Fluid Mechanics and Thermodynamics at the University of New South Wales. He has also spent periods in visiting positions at the University of Cambridge and the Massachusetts Institute of Technology. He is currently working in the area of ship dynamics and propulsion, with particular reference to high speed ship motion and wave loads, and has published and acted as consultant in heat transfer, fluid dynamics, vibration and noise.

Michael is a Fellow of the Institution of Engineers, Australia and a Fellow of the Royal Aeronautical Society.

Damien S Holloway

Damien Holloway currently lectures at the University of Tasmania in the areas of stress, structural analysis and dynamics. He completed a BE(Hons) in civil engineering at the University of Tasmania in 1992, graduating with a University Medal, followed at the same institution by a PhD in ship hydrodynamics, completed in 1998. He has held postdoctoral positions in both Mathematics (free surface groundwater problems) and Engineering (ship hydroelasticity), and worked as a consulting civil/hydraulic engineer.

Timothy Roberts

Tim Roberts is a director and the Research and Development Manager at Revolution Design. This involves the co-ordination of the design drafting, marketing and construction groups in the development of existing and future designs of aluminium fast ferries. He is responsible for research into all facets of high speed ship building and design and the application of this research into the production of fast ferries and cargo vessels. Particular areas of research include tank model testing and computer modeling of catamaran hull shapes, propulsion specifications, finite element analysis of global structure, material property testing & fatigue analysis of welded joints for various alloy combinations and full scale monitoring of vessel motions, stresses and sea conditions for the prediction of sea loads on high speed vessels. Tim holds a Bachelor of Mechanical Engineering and a Masters of Engineering Science.