Optimal lateral aseismic performance analysis of mega-substructure system with modularized secondary structures

Summary A major type of mega-substructure system is yet to fulfill its full potential of vibration control because of the fragility originating from excessive inter-story drift of its secondary structures during earthquake. We propose an innovative subtype of mega-substructure system to overcome this fragility and further improve its lateral aseismic performance. This subtype takes advantage of modular construction techniques. The secondary structures, which consist of suspended discrete modules, provide protection to nonstructural members against excessive inter-story drift. Additionally, springs that provide inter-story stiffness remain elastic. These effects extend the inter-story drift limit of secondary structure and make sufficient relative motion possible. We carried out single-objective and dual-objective optimizations to derive optimum parameters and capture the potentials of representative models. Mean square responses under power spectral density functions of ground acceleration were set as optimization objectives. It is shown that the proposed systems further suppress the response of primary structure at the expense of additional response of secondary structure, which can be accommodated by the aforementioned protection effect. Mechanisms are revealed in the perspective of transfer function curves. Robustness and time history performances are also verified.