Modern buildings are becoming more and more irregular and complex in shape. These irregular buildings with misalignment of the centers of mass (CM) and the centers of rigidity (CR) may vibrate during earthquakes in a lateral-torsional manner with significant swaying and twisting motions. The objective of this research is to develop an innovative computer-based design method for optimal structural topology design of buildings, achieving a satisfactory torsional performance under seismic actions.

This thesis presents a transformation technique for decoupling the combined translational and torsional seismic effects on irregular buildings with three dimensional (3D) mode shapes. Using the effectively uncoupled system, the uncoupled periods and the representative building eccentrici...[ Read more ]

Modern buildings are becoming more and more irregular and complex in shape. These irregular buildings with misalignment of the centers of mass (CM) and the centers of rigidity (CR) may vibrate during earthquakes in a lateral-torsional manner with significant swaying and twisting motions. The objective of this research is to develop an innovative computer-based design method for optimal structural topology design of buildings, achieving a satisfactory torsional performance under seismic actions.

This thesis presents a transformation technique for decoupling the combined translational and torsional seismic effects on irregular buildings with three dimensional (3D) mode shapes. Using the effectively uncoupled system, the uncoupled periods and the representative building eccentricity are evaluated. Since the uncoupled periods directly relate to the translational or torsional stiffness of a building, the element stiffness contributions to respective stiffness for resisting either pure translational swaying or pure torsional twisting can be quantified. To design a building without significant seismic torsional effects, the constraints of the ratio of uncoupled torsional to translational periods and the ratio of maximum-to-center seismic displacements are imposed and explicitly expressed in the optimization formulation framework.

By incorporating the concepts of Sewall Wright’s shifting balance theory of evolution (SBT), an innovative evolutionary based topology optimization method, namely the Shifting Balance Genetic Algorithm (SBGA) method has been developed for structural layout optimization of buildings. As compared with the standard GA, the SBGA introduces the concept of population subdivision and emphasizes the role of migration and crossbreeding in adaptive evolution. Using the SBGA method, not only can useful population diversity be preserved, but also an even balance can be struck between exploration of the design space and exploitation of the location evolution during the searching process. Therefore, the SBGA method hybridized with the efficient element sizing optimization technique, that is the Optimality Criteria (OC) technique, can enhance the robustness of the algorithm to obtain the optimal structural topology and element sizing design. To further increase the computational efficiency in solving the structural topology optimization problem of practical large-scale buildings, a multi-stage optimization approach has been devised by decomposing a large topology design problem into a set of smaller and more tractable sub-problems, which are sequentially solved by the evolutionary topology optimization algorithm. Finally, a number of practical building examples are presented in the relevant chapters which successfully demonstrate the efficiency, robustness and practicality of the proposed evolutionary based topology optimization method.