Probability-based Design of an Optimal Elastic–plastic Truss / Optimalios Tampriai Plastines Santvaros Projektavimas Tikimybiniu Statistiniu Metodu

According to Eurocode EN 1990 and Lithuanian Technical Regulation of Construction STR 2.05.03:2003, structures should be designed to satisfy reliability requirements. The reliability of a structure can be achieved using one of 3 methods: partial factor (PF), PF assisted by testing and direct probability-based method. When PF methods are used, the determined reliability of a structure is often greater than required; therefore the direct probability methods allow a more cost-efficient design. The reviewed literature suggests that even greater economical effect can be achieved by combining probability-based design methods with optimization. Unfortunately, the literature presents very few such methodologies. This article focuses on an optimal design of a truss under variable repeated loading at shakedown. The authors propose a model of a truss volume minimization problem with direct probabilistic evaluation of safety margin. The developed technique allows finding minimum volume of desirable reliability structure when loading, provided stochastic parameters are known in advance. The finite element method is applied for the discretisation of a structure. Mathematical programming is used to resolve the optimization problem.