Thesis (M.Eng.)--Chulalongkorn University, 2012

This study proposes a Heuristic Algorithm for the optimal design of steel frame structures using the Direct Analysis Method of the AISC 2010 Specification. The objective of the design algorithm is to obtain the minimum weight of the steel frame sections where the design constraints are imposed by the AISC-LRFD specification requirements. In this paper we combine the CSi SAP2000 commercial structural analysis program with the Heuristic Algorithm which is written in Microsoft Visual Basic program for the optimal design of steel frame structures. The analyses are performed by using the first-order analysis method without P-Delta effects and the rigorous second-order analysis with P-Delta effects to illustrate their effects on structural optimal design. Through three examples of planar steel frames, we firstly compare the results between the Direct Analysis Method and the conventional methods which are the Effective Length Method and the First-Order Analysis Method, and then followed by the comparison of the efficiency of the Heuristic Algorithm with the optimization algorithm such as Genetic Algorithm, Ant Colony Optimization, Harmonic Search algorithm, and the virtual work based optimization for lateral deflections in software CSi SAP2000.