1. Introduction
This paper proposes a design method utilizing Building Mass Damper (BMD) system for the mid-story isolation structure. In general, it is well known that Tuned Mass Damper (TMD) is required a larger auxiliary mass in order to exert damping effect against large-scale earthquake. BMD is a creatively system which can construct a larger auxiliary mass by utilizing the entire upper structure as an auxiliary mass. This paper proposes optimal design conditions of BMD based on complex eigenvalue analysis. Assuming an actual design, optimal design conditions are proposed for three cases of the lower structure, the upper structure, and the lower and the upper structures. Furthermore, it shows the design method of the isolation layer performance which satisfies the target response performance by using the performance based design diagram. In addition, it shows the flowchart of the proposed design method and the definite design example. By using this design method, it is possible to determine the parameters of the mid-story isolation layer which satisfy the target performance without performing the time history response analysis.
2. Optimal design equations of BMD
BMD can reduce the response by tuning the upper structure and the lower structure through the isolation layer. BMD can be represented by the 2 degrees-of-freedom (DOF) system by reducing upper and lower structures respectively. For this reason, optimal design equations are derived based on the invariant point theory as relational of the natural period for the 2 DOF system. It shows the design examples applying the optimal design equations and verify the validity of the proposed optimal design equations.
3. Outline of design method using the performance based design diagram
The traditional problem on the design of the seismic isolation structure is that it is necessary to repeatedly assume the combination of the base isolation layer parameters until satisfy the target performance and to confirm by time history analysis. In order to solve this problem, I.Hata and S.Ishimaru et al. proposed the seismic design method using the performance based design diagram. This design method can predict the maximum response of the 1 DOF system with the elasto-plastic properties. By using this design method, it is possible to design the isolation layer performance which satisfy the target performance without performing the time history response analysis.
4. Design method of BMD
This section shows the flowchart of the proposed design method of BMD by using the performance based design diagram. In addition, it shows the design example of BMD following the proposed design flowchart. It verifies the validity of the proposed design method through the design example with the lower structure as the design target. Using proposed design method, it is possible to optimally design by the same design procedure even when the upper structure and the lower and the upper structures are targeted.
5. Conclusion
This paper proposes the design method for BMD applied to mid-story isolation structure. The optimal design equations of BMD based on complex eigenvalue analysis are derived, and it shows that the effectiveness of the proposed design method through the design example. From the above, it shows that the proposed design method can be applied to design of BMD using mid-story isolation structure.
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