This thesis presents a computer-based method and development of a computer program for optimally sizing members of 3-dimensional steel frameworks using commercial standard sections. For static and dynamic loads, a minimum weight structure is found while simultaneously ensuring stress and displacement performance conditions under applied service loads.
The algorithm first finds the optimum design variables under the assumption that the principal design variables can be varied continuously, and other design variables are obtained using curve fitting of section data-base. The principal design variables mean one size of section that influence the section properties considerably.
Then the Phase-I search is performed to find a feasible discrete solution from a point which is near the optimum design but is in the infeasible set. The solution is further improved in the Phase-II search, to obtain the final discrete optimal design of the problem.
A computer program is written to test validity and efficiency of the algorithm with various examples of minimum weight for beam-truss structures.
As the results, it is found that the algorithm is highly stable and can be readily applicable to various structural optimization problems with discrete set of specified design variables.
