Determination of Optimal Configuration for Mega Bracing Systems in Steel Frames using Genetic Algorithm

Abstract

Mega bracing is one of the recently emphasized methods for lateral bracing of structures. In the present study, various configurations of mega bracing systems in terms of installation angle for lateral bracing of steel structures are evaluated and optimized. The investigated frames are designed and optimized using genetic algorithm (GA) according to LRFD-AISC (load and resistance factor design, american institute of steel construction). Frame analysis is carried out by means of finite element method, while optimization is conducted using GA considering three different types of selection and crossover, simultaneously. The results demonstrate that the optimum angle of mega bracing in steel frames is within the range of 36° to 42° with regard to the frame height and span. Furthermore, with increase in frame height, the employment of optimally distributed mega braces along the height of the frame results in reduction of story drifts and also the frame weight. Additionally, simultaneous utilization of various selection and crossover types in GA optimization leads to an increase in convergence rate of optimum weight of the frame as well as reduction in the required computations.