Adaptive reduced integration method for nonlinear structural dynamic analysis

The development of a reduced integration method, based on a Ritz-Wilson type reduction technique, for the nonlinear dynamic analysis of large-scale structural systems is presented. Particular consideration is addressed to compliant structures for deepwater oil exploration and production, which present severe geometric nonlinear effects and thus require the use of an incremental-iterative ( i-i) formulation. Several aspects are considered in order to improve the computational efficiency of a reduced integration method when applied to this class of problem, including: the algorithm for the generation of the Ritz basis; termination criteria for this algorithm; the formulation of the reduced equations of motion; and the calculation of the reduced matrices. The utilization of a version of an adaptive time integration strategy, which automatically calculates time step values and triggers stiffness and basis re-evaluations, is also addressed and plays an essential role in the performance of the presented method. An application of these developments on the nonlinear dynamic analysis of a compliant guyed tower is presented, and the results are discussed in order to evaluate the computational performance of the method.