Performance Validation of Inter-Story Isolation Through Shake Table Real-Time Hybrid Simulation

Abstract eng:
While traditional base isolation remains one of the most widely employed systems for mitigating seismic response, interstory isolation has recently gained popularity, especially in densely populated areas. In inter-story isolation, the isolation system is incorporated between stories instead of the base of the structure. Installing inter-story isolation is simple, inexpensive, and disruption-free in retrofit applications. Benefits include nominally independent structural systems where the accelerations of the added floors are greatly reduced when compared to a conventional structural system. Furthermore, in retrofit applications, the base shear demand on the total structure is not significantly increased. Practical applications of inter-story isolation have appeared in the US and Japan and likewise new design validation techniques are needed to parallel growing interest. Real-time hybrid simulation (RTHS) offers an alternative to investigate the seismic behaviors of high-rise buildings with inter-story isolation. Shake tables are standard equipment in many laboratories, ranging from simple uniaxial tables to six-degree-of-freedom tables. These tables are capable of providing the interface boundary conditions necessary in this application of substructure RTHS. The substructure below the isolation layer can be simulated numerically while the superstructure above the isolation layer can be tested experimentally. This provides a high-fidelity representation of the nonlinearities in the isolation layer, including any supplemental damping devices. However, implementation of RTHS using shake tables is challenging. Shake tables are nonlinear devices exhibiting strong control-structure interaction, making modeling and control a challenging task. Any delay or lag in the realization of the desired table trajectory and measurement of the base shear can introduce inaccuracies and instabilities into the loop. This research investigates the seismic performance of a 14-story high-rise building with inter-story isolation through shake table RTHS. Challenges associated with shake table RTHS are addressed throughout this practical application. To contrast the challenges, the favorable behavior of base-isolated specimens in RTHS from a stability perspective is illustrated. A model-based shake table control approach is successfully implemented on the shake table, exhibiting good offline and online acceleration tracking performance. The methods proposed show that RTHS is an accurate and reliable means to investigate high-rise buildings with inter-story isolation, including new configurations and supplemental control approaches.

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