A Genetic Algorithm based Optimum Bracing Design of Non-Sway Tall Steel Frames

Abstract

This paper presents genetic algorithm based optimum design method for multi-storey non-swaying steel frames with different types of bracing. The design method obtains a frame and bracing system with the least weight by selecting appropriate sections for beams, columns and bracing members from the standard set of steel sections. The algorithm accounts for serviceability and strength constraints as specified in BS 5950. The serviceability limit state included in the design problem is achieved by limiting the overall and intermediate storey drift in the building to height/300 as specified by the code. The strength constraints are in the form of inequalities as designed in BS 5950 which ensures that the design capacity of the member is greater than the ultimate force it is subjected to. The design algorithm takes into account lateral torsional buckling of frame members, if they are beam-columns. Bracing members are considered to be made out of back to back double equal leg angle attached to the gusset plates. The algorithm presented is used to design number of tall frames with different bracing systems such as X, V and Z bracing. It is noticed that X-bracing produces the lightest frame among the others.