BV: Warping Analysis Cures Fatigue Cracking

Bureau Veritas says detailed warping analysis is the key to a crack-free new generation of containerships. "Some large containerships appear to be suffering cracking of longitudinals caused by fatigue and warping stress," says Pierre de Livois, technical director of Bureau Veritas Marine Division. "We are pleased that the many Panamax and post-Panamax containerships built with Bureau Veritas class show that extensive Finite Element Model analysis and attention to fatigue and structural details at the building stage have paid off. They are not showing this typical cracking in the side longitudinals."

De Livois says, "We have been able to incorporate all our positive experience into different series of containerships built this year in various shipyards. We were able to check the designs against the most recent developments of sophisticated fatigue analysis during the very preliminary design stage, and during the engineering detailed development. Our latest software tools for structural and fatigue analysis allow us to meet all class requirements in terms of scantling and connection details, and also help to achieve the best compromise in term of cost/benefit for both owner and shipyard." Ludovic Gerard, CMA CGM Newbuilding says, "This early stage approach, working closely with the class society on a new project, is without any doubt a safety and cost benefit scheme. In partnership, we for instance managed to decrease the fatigue restraints of our 5,770 TEU containerships built by Samsung in 2004, without any additional structural requirement."

Fatigue is a complex phenomena which requires careful feed-back experience analysis and continuous development of dedicated calculation methods and tools. Bureau Veritas has invested accordingly for a long time to achieve leadership in this field, and its experience in practice highlights the undeniable effects of design optimization and safety benefits shared by the shipowners and shipyards.