Seismic control of modularized suspended structures with optimal vertical distributions of the secondary structure parameters

Abstract

Suspended building systems with vibration control features dissipate seismic energy by the interaction between their main parts and the suspended parts; they are also architecturally appealing. A modularized suspended structure has been previously proposed to overcome the fragility of its secondary structure and to enhance overall attenuation. However, the full potential of modularization is yet to be achieved via the previous configuration, especially in terms of multi-mode control. In this study, the protection effect of prefabricated modules is further harnessed in such a way that drastic vertical-irregularities of inter-story stiffness and dampers within the suspended segment are allowed. Vertical distribution vectors of structural parameters were set as the variables in genetic-algorithm optimizations, with the maximum mean square moment of the primary structure being the main objective. The results show considerably improved attenuation of responses in multiple modes instead of only the fundamental mode. In the optimized distributions, peaks of damping coefficient occur at the troughs of inter-story stiffness, but without a highly concentrated pattern. Models with different irregularity levels have well-separated Pareto fronts; this indicates that comprehensive improvement can be obtained at compromised choices. The main mechanism is that, with the well-designed irregularities, the secondary structure provides satisfactory dissipation and tuning to the primary structure in the major modes. The analysis with non-stationary excitations reveals that optimized vertical distributions further quicken the vibration decay. The time-history performance verifications and the structural uncertainty analysis are also carried out.