Abstract: GFRP catamaran has more dangerous situations than the steel ones under the multiple conditions. It needs to consider its particularity hull strength materials and structures when calculating its structural strength. Now very few research and attention is taken on it. In this paper, by taking the GFRP catamaran as the research object, 10 kinds of major dangerous working conditions are selected as the calculating conditions according to the structures and the actual sail area, using the finite element method to calculate its structural strength under the combined effects of multiple conditions. To change the traditional way of independent analysis towards the dangerous section, the quadratic assignment correction method was presented. The results show that torsion, transverse bending, torsion-transverse combination conditions are the main reason of strength failure. Torsion conditions are the main reason of strength failure. Also, it finds the dangerous conditions and structures which is sensitive to the change of principal stress, and the variation regularity of maximum/minimum principal stress of GFRP panels. Besides, some local structures designed by traditional method are still dangerous. The research methods and conclusions have reference value on the strength calculation of composite yacht.

Key words: glass fiber reinforced plastic, catamaran, structural strength, finite element method, principal stress