Reliability-based optimization of structural systems

A method to carry out a Reliability-Based Optimization of especially nonlinear structural systems is introduced. Statistical uncertainties involving both structural and loading properties are considered. The concept is based on the separation of structural reliability analyses and the optimization procedures. Two approaches are discussed, depending on the interaction of reliability analysis and mathematical programming and the way of representation of the limit state functions (LSF) of the structure. As, for cases of practical significance, the LSF is known only pointwise it is approximated by Response Surfaces. For the response calculations Finite Element procedures are utilized. Failure probabilities are determined by applying variance reducing Monte Carlo simulation techniques such as Importance Sampling. Following the reliability analysis, the optimization procedure is controlled by the NLPQL algorithm. A numerical example in terms of a template ocean platform exemplifies the procedures.