Mahmoud R. Maheri - Corresponding author, Professor of Civil Engineering, Faculty of Engineering, Shiraz University
Ghasemi - Postgraduate student, Department of Civil Engineering, Shiraz University, Shiraz, Iran

In a multi-storey, multi-bayed three-dimensional frame, the choice of positions of the braces is affected by two main considerations namely; the architectural limitations and the optimum positions for the cheapest and the most effective design. Architectural limitations are generally determined by the architect prior to the engineering design. The optimum position of the braces for design purposes, however, should be determined by the designer and according to the applied loading, serviceability requirements and the architectural layout of the building. In this paper, the locations of X-braces in three-dimensional frames are optimized using an adaptive genetic algorithm with self-adaptive penalty functions and dynamic crossover and mutation operators. Some independent constraints including the number of braced panels and the architectural location limitations are also incorporated. Results of the GA brace topology optimizations on one, two and three-storey, 3-D non-symmetric steel frames with the emphasis on minimising the weight of the steel as well as reducing the torsional displacements and lateral drift are compared with those of the conventional brace topologies with markedly favourable results.