Recent Advances in Optimal Design of Structures from a Reliability Point of View

摘要

Structural optimisation and structural reliability theory are considered. Both of these areas have developed during the last two decades from being of purely theoretical interest to areas useful in practical design. The main elements of structural reliability theory are described in the second section. First, a short review of the reliability theory for structural elements (e.g., beams and tubular joints) based on the so-called ß-index philosophy (Cornell[1], Ditlevsen[2], and Hasofer and Lind[3]) is given. Detailed descriptions are given in textbooks such as those by Thoft-Christensen and Baker[4] and Madsen et al.[5]. Next a heuristic method, the so-called ß-unzipping method[6] is mentioned. This method can be used to estimate the reliability of a structural system if some modelling assumptions are fulfilled. In the third section some elements of structural optimisation theory are described. A reliability-based structural optimisation problem is formulated. The formulation is a natural extension of the commonly used formulations in deterministic, classical structural optimisation. Some methods for solving the reliability-based optimisation problem are mentioned[7, 8, 9, 10]. In the fourth and fifth sections two examples of optimisation with reliability constraints of steel-jacket offshore platforms are given. In the first example special consideration is given to the reliability of the tubular joints and in the second example a three-dimensional model is considered.