Abstract: The present invention provides a method and apparatus for analyzing the structural response of an object having an outer surface comprising a plurality of surface portions, the method including: forming a three dimensional model of said object, said model comprising a surface mesh representative of said outer surface and comprising a plurality of eccentric shell elements, wherein each of said elements is defined by a plurality of nodes on said surface and each of said nodes has one or more degrees of freedom; assigning to each of said elements a thickness indicative of half of the thickness of said object at said respective element; defining, for each of said elements, a reference surface that includes the nodes of said respective element and that is coincident with said surface mesh at said respective element; for a pair of opposed portions of said surface, establishing a constraining relationship between said degrees of freedom of each of said nodes on the first of said opposed portions and said degrees of