Study On Optimal Design Of Steel Frame Systems

Steel frame systems including steel frames with and without bracing systems are common structural systems used in multistory and high-rise steel buildings, especially in steel structure dwelling houses. How to design the steel frame systems quickly, economically and reasonably (i.e., how to optimal design the steel frame systems) has become a bottleneck problem for the development of steel structure dwelling houses. Optimal design of multistory and high-rise steel frame systems is a complex and synthetic structure optimization problem, for it involves many aspects in the field of optimization. Viewed from optimization level, it includes size optimization and topology optimization; and viewed from optimization type, it contains single- and multi-objective optimization; and viewed from optimization method, it involves size, topology, single- and multi-objective optimization algorithms. Just for those reasons, it is difficult to some extent to research this optimization problem.In this paper, optimization design of steel frame systems is studied systematically for the first time from two aspects: steel frames and bracing systems.First of all, considering the fact that all the beam-to-column bolted connections in steel frames are characterized by the behavior of flexibility in reality and should be modeled as semi-rigid connections, optimum design of steel frames with semi-rigid connections under static loading is investigated. Element stiffness matrix in local coordinate system is derived, which takes the effects of the flexibility of connections and the geometric nonlinearity of the members into account, and element fixed-end forces with semi-rigid connections are modified. A computer-based procedure with incremental loading method is presented for the analysis of semi-rigid steel frames, which accounts for the nonlinear behavior of the connections and P-Δ effect as well as the coupling effect of element forces and connections. According to practical engineering, an optimization mathematic model for design of semi-rigid steel frames with the minimum cost of members and connections is proposed, and a modified genetic algorithm (GA) is used to optimize the model. Several examples of steel...