Trenching and elevating models of Cased Insulated Flowline with nonlinear bending stiffness

Tension cracking and compression collapse of concrete-weighted coats are carefully included to build up the nonlinear relationship between bending stiffness and curvature of Cased Insulated Flowline system. Based on this nonlinear bending stiffness trenching and elevating models of this kind of insulation system are built to calculate the additional moments in the Field Joints and the damage of concrete-weighted coat in those installation statuses, and even the shear forces in CIF pipe coats. Moreover the analytical formulae describing the static response of CIF systems on an elastic foundation are developed by transfer matrix method.