Design optimization of tubular lattice girders

Abstract

The lattice girder, members of which are constructed by use of ready profiles with tubular cross-sections, has a simple but an effective structural framing form. In this regard, this study proposes to optimize the design of tubular lattice girders in a way of minimizing its entire weight and joint displacement and maximizing its load-carrying capacity considering the design codes of API RP2A-LRFD. As an optimization tool, a multi-objective optimization methodology named pareto archived genetic algorithm (PAGA) was utilized. The search capability of PAGA was improved by involving a designer module for automatically creation of a lattice girder form. The improved PAGA has a big responsibility of increasing the convergence degree of optimal designs against the stability problem. Furthermore, the content of this study is enriched by evaluating the computing efficiency of PAGA with respect to several multi-objective optimization algorithms. Consequently, the improved PAGA achieves to explore the optimal lattice girder designs with the higher convergence, diversity and capacity degrees. Therefore, the proposed optimum lattice girder design tool is recommended for the designers due to its capability of obtaining a wide range of promising designs.