Analytical and experimental studies on midstory isolated buildings with modal coupling effect

Abstract

SUMMARY In a midstory isolated building, the isolation system is incorporated into the midstory rather than the base of the building. Because of the flexibility of the substructure below the isolation system in a midstory isolated building, the contribution of higher modes to the seismic responses of the midstory isolated structure may not be negligible, especially when the coupling of higher modes exists. To investigate this modal coupling effect, a simplified three‐lumped‐mass structural model of the midstory isolated building is assumed in this study. Through the equivalent linear analysis and shaking table tests, it is found that the coupling of higher modes may lead to enlarged acceleration responses at the super‐floor and superstructure above the isolation layer. Accordingly, a simple method to prevent the midstory isolation design from the coupling of higher modes attributed to the improper design of the substructure and superstructure is proposed in this paper. Copyright © 2012 John Wiley & Sons, Ltd.

Optimal energy‐based seismic design of non‐conventional Tuned Mass Damper (TMD) implemented via inter‐story isolation

“…The isolation system located below the i th floor segments the N ‐story frame structure into a lower (L) portion and an isolated upper (U) portion, corresponding to N L = i − 1 and N U = N − i + 1 Degrees Of Freedom (DOF), respectively (Figure (a)). In the present paper, the two structural portions are also denominated as substructure , the former, and superstructure , the latter .…”

Optimum dynamic characteristic control approach for building mass damper design

“…It is because that the OBMD specimen is designed based on a more comprehensive objective function, while MSI is designed only considering the seismic performance of the isolated SUP. Therefore, in the future study, the proposed optimum dynamic characteristic control approach might also be applied to the mid‐story isolation design to effectively solve its response amplification problem at the SUB . The maximum inter‐story displacement at the isolation layer of MSI under all the earthquake inputs as listed in Table is 44.7 mm.…”

“…Therefore, in the future study, the proposed optimum dynamic characteristic control approach might also be applied to the mid-story isolation design to effectively solve its response amplification problem at the SUB. [4][5][6] The maximum inter-story displacement at the isolation layer of MSI under all the earthquake inputs as listed in Table 3 is 44.7 mm. In general, the inter-story displacement response at the CL of the OBMD specimen is much smaller than that at the isolation layer of MSI.…”

“…The excellent performance of seismically isolated buildings during past earthquakes has encouraged the adoption of seismic isolation technology for structural and non‐structural protection . Among the increasing practical applications, the mid‐story isolation design, in which the isolation system is usually installed on the top of the first story of a building, is recently gaining popularity owing to its advantages in terms of construction efficiency, space use, and maintenance over the conventional base isolation design . The seismic performance of mid‐story isolated buildings has been thoroughly investigated .…”

“…Among the increasing practical applications, the mid‐story isolation design, in which the isolation system is usually installed on the top of the first story of a building, is recently gaining popularity owing to its advantages in terms of construction efficiency, space use, and maintenance over the conventional base isolation design . The seismic performance of mid‐story isolated buildings has been thoroughly investigated . It was indicated that the mid‐story isolation design is effective in reducing the seismic demand of the superstructure (SUP) above the isolation system if the coupling of higher modes is precluded.…”