The Development of a New 3D Rotational Seismic Isolation System

Abstract eng:
Vertical earthquake components are usually insignificant during seismic analysis and design, whereas a safe design for the horizontal seismic responses is assumed to accommodate the forces generated due to vertical seismic excitations. This assumed safety limit is in accordance with the acceptance criteria specified by some of the major design standards that deal with vertical seismic accelerations. While the aforementioned approach may be true for some types of structures or areas of a certain level of seismicity, there are multiple considerations that could invalidate this approach. Such considerations can include types of structures that contain dangerous chemical substances or those which are of critical national importance such as nuclear power plants. Furthermore, time history records for multiple earthquakes such as TAFT, KOBE and HACHINOHE combined with horizontal seismic isolation for certain types of heavy structures have shown a significant response in the vertical direction that could not be accommodated by traditional design methods indicated within most seismic design standards. Previous investigations such as that carried out for 3D seismic isolation of Fast Breeder Reactors in Japan have introduced 3D seismic isolation within the engineering community, where this study has shown the significance of the vertical earthquake components on these types of structures as well as offering particular concepts and strategies that can be used to mitigate such responses, these concepts are briefly introduced. As there is an obvious need for more research in this area, where there are only a few concepts covering vertical seismic isolation worldwide, this paper introduces a research project carried out in order to verify a new concept for a 3D seismic isolation device called 3D Rotational Seismic Isolator abbreviated as 3DRSI. This device was developed and investigated as a part of an ongoing research to obtain economical and flexible solutions for mitigation of both horizontal and vertical seismic excitations. The target of this research was achieved by the development of the concept, defining components, researching the variable parameters, testing of three specimens to verify the mechanical and energy dissipation characteristics.

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