Intrinsic coordinate elements for large deflections of offshore pipelines

A numerical method for solving large deflections of elasticas and offshore pipelines is described. The method is based on finite element analysis usin g intrinsic coordinates, namely the nodal rotations and the are length. The element stiffness is independent of element orientation and the displaceme nt vector is expressed in terms of nodal values of cross-sectional rotation . The generation of the vector of integrating coefficients for numerical in tegration adopts the quadrature method, which is subsequently assembled int o a quadrature matrix. The element lengths are embodied in the vector of in tegrating coefficients and such lengths are not constrained to be uniform. This feature fits in very well with the intrinsic coordinate elements. The transformations that are required from intrinsic to Cartesian coordinates a ffect only the Load vector in the equilibrium equation. Consequently some c omputational advantages can be expected from the intrinsic coordinates form ulation, particularly for large deflection problems.