Partial mass isolation system for seismic vibration control of buildings

Abstract

Summary In a previous study, the authors studied a partial mass isolation (PMI) system that through isolating different portions of story masses can provide a building with multiple inherent vibration suppressors. It was shown that the PMI strategy with isolated mass ratios (IMRs) of 0.05 or 0.90 could perform as effectively as an equivalent tuned mass damper or a base isolation system, respectively. In the present paper, the PMI system is examined in structural models with different fundamental periods. PMI configurations in a wide IMR range of (0.05:0.025:0.90) are optimized illustrating that applying an IMR of 0.25–0.50 can provide an efficient system, simultaneously satisfying the constraints related to different performance objectives (i.e., mitigating the overall building seismic responses and controlling isolated components' (ICs) responses while integrating these components into the building architecture). Simulation results reveal that using identical ICs at different stories, which have the advantage of facilitating the design and construction of the system, can lead to a near‐optimal solution. It is also demonstrated that in terms of the spatial distribution of ICs, an adequate seismic performance improvement can be achieved by allocating ICs only at a subset of upper stories (e.g., top half stories), which can further simplify the PMI systems' construction.

Robust design of a multi-floor isolation system

“…In previous works, the authors studied MFI configurations with different isolated mass ratios (IMRs) in 6-, 12-, 20-, and 40-story buildings. [20,21] A deterministic design optimization was conducted through minimizing interstory drift responses of the structural frame under stochastic excitations. It was shown that an MFI system with a low IMR (e.g., 5%) provides sufficient inherent mass to negate the need to add an external mass damper to the system; at a high IMR (e.g., 90%), an MFI system exhibits a global dynamic response reduction similar to the one obtained using a traditional BI system.…”

“…It was shown that an MFI system with a low IMR (e.g., 5%) provides sufficient inherent mass to negate the need to add an external mass damper to the system; at a high IMR (e.g., 90%), an MFI system exhibits a global dynamic response reduction similar to the one obtained using a traditional BI system. Taking into account different performance objectives that deal with the mitigation of structural interstory drift, displacement and acceleration responses of isolated floor subsystems (IFSs), and structural and architectural constraints, Anajafi and Medina [20] showed that applying intermediate IMRs (e.g., 25-50%) can provide an effective and efficient MFI system.…”

“…isolated floor subsystems (IFSs) and an isolated mass ratio of 50% designed on the basis of different scenarios. gMFI = multi-floor isolation with generic (dissimilar) IFSs at different stories; iMFI = multi-floor isolation with identical IFSs at different stories; SM = sensitivity measure FIGURE 18 Performance sensitivity of the multi-floor isolation (MFI) system with top 10 isolated floor subsystems (IFSs) and an isolated mass ratio of 50% with respect to aleatory variabilities: (a) MFI with identical IFSs at different stories, J s drift is minimized; (b) MFI with generic (dissimilar) IFSs at different stories (gMFI), J s drift is minimized; (c) gMFI system, max (|H(ω)|) over the given uncertainty range is minimized; and (d) gMFI system, max (sensitivity measure [SM]) over the given uncertainty range is minimized 7 | CONCLUSIONS An MFI system, which was proposed by the authors in a previous study, [20] is evaluated herein in terms of its effectiveness and robustness to mitigate earthquake-induced interstory drift demands in buildings. The proposed MFI system is based on the isolation of different portions of floor masses at various locations throughout the height of the building such that the isolated masses serve as inherent vibration suppressors.…”

“…In an MFI approach, main floors are isolated from the superstructure at several stories to provide a building with multiple inherent vibration suppressors without imposing any additional mass to the building. [18][19][20][21] As part of this study, several MFI configurations are deterministically optimized for a test-bed 20-story structure. Then, the sensitivity of the seismic performance of the optimally designed configurations with respect to deviations in the design parameters is investigated.…”

Optimisation Design and Damping Effect Analysis of Large Mass Ratio Tuned Mass Dampers

“…en, the nontraditional large mass ratio (>0.15) TMD is formed, such as the structure local isolation [6], the megasubstructure configuration [14,15], and the interlayer isolation structure system [16,17]. e noncritical components in the structure, such as filled walls and floors, can also be used as the mass blocks to form a large mass ratio TMD [18,19]. In addition, the heavy equipment in an industrial plant can be constructed into a large mass ratio TMD in the form of suspension or isolation [20].…”