GA-Based Optimisation of Dissipative Knee Braced Steel Frames

Knee bracing system is a lateral earthquake resisting system which combines the feature of lateral stiffness and energy dissipation capacity. The concept relies on the strategic placement of hysteresis dissipative elements to yield (form plastic hinges) in the first instance and absorb energy to protect the main frame. This paper proposes an intelligent procedure to optimise the seismic performance of knee braced frames. For this purpose, a genetic algorithm (GA) is elaborated to determine the strength distribution of the knee elements to optimise the energy dissipation through the building height. The strength limits of the knee elements are considered as the individual genes, and a first population is randomly generated within a predefined range of variation. The population is evolved through adequate crossover and mutation operations. The objective function is the total hysteresis energy dissipated by the knee elements. The results show that the algorithm is efficient and robust in generating optimal distributions of the knee elements strengths for different frame configurations.