Feasible numerical analysis of steel lazy-wave riser

Feasible numerical method for the structural analysis of a Steel Lazy-Wave Riser (SLWR) static configuration is presented. The method considers the whole riser, which includes a buoyancy section and is partially suspended and partially laid on a seabed, as a single continuous segment. The riser is modeled by means of nonlinear large deformation beam theory. The numerical solution is carried out in an incremental-iterative manner allowing efficient treatment of riser-seabed interaction circumventing the complexities with contact detection. At each increment, a new sequential equilibrium configuration is assessed by direct minimization of a total potential energy approximated as a Riemann sum, which yields algebraic system of nonlinear finite difference equations that is further solved iteratively with Newton-Raphson technique. The method does not require as an input a predefined length of the riser but allows its definition from the analysis. The method is validated with Abaqus. Representative parametric study is conducted to demonstrate the feasibility of the method. Considered the effects of the upper section length, the buoyancy section length, uplift loading ratio, the horizontal top tension and ocean current. The simplicity, flexibility and robustness of the proposed method allow to enhance the efficiency of the engineering calculations and the design.