An Innovative Application of Base Isolation Technology

Dutta, Anindya; Sumnicht, John F.; Mayes, Ronald L.; Hamburger, Ronald O.; Citipitioglu, Ahmet

doi:10.1061/41000(315)13

Cited by 7 publications

(3 citation statements)

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“…By installing the upper seismic isolation system on the top of the existing buildings, the MSI technology is proved to be an effective strategy for adding the new function to existing buildings [12][13][14][15]. By inserting the isolation devices into the existing buildings, MSI technology has also been reported for the reinforcement of historic structures in accordance with the current design criteria [16]. Kim and Kang [17] installed magnetorheological (MR) dampers into the MSI system, which proved to be capable of reducing the displacement demand of the MSI system.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

Song

Xue

2021

Shock and Vibration

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At present, the midstory isolation (MSI) technology has great potential for application in historical buildings’ retrofitting and multifunction buildings. The coupling effect due to the variability of the location of the isolation layer may amplify the structural seismic response and is required for in-depth analysis. This paper aims to evaluate the magnitude of the coupling effect and delimitate the region of the coupling effect to be considered. Based on the complex mode superposition method, the explicit formulas for calculating the random response of the simplified model are deduced. The root-mean-square (RMS) ratio of the shear force coefficient of the upper isolation system is adopted as the performance indicator to evaluate the coupling amplification effect of the MSI system. Parameter analysis indicates that the coupling region is closely related to the mass ratio and frequency ratio of the upper and lower structures to the isolation layer. In general, the region of the coupling effect to be considered can be divided into two parts according to parameters of frequency ratios, depending on the thresholds of the performance indicator. As the mass ratio of the upper isolation system to the entire system increases, one of the coupling regions shrinks and eventually disappears, indicating that the coupling amplification effect in this region can be neglected under certain conditions. Finally, the time-domain analysis of three representative numerical cases of MSI buildings was performed to verify the reliability of the results obtained from the frequency-domain analysis. The research results can provide technical guidance for the preliminary design of the MSI buildings.

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Section: Introductionmentioning

confidence: 99%

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

Song

Xue

2021

Shock and Vibration

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“…Obviously, the vertical capacity of the existing structural system including the foundation must be able to support the additional stories; otherwise, retrofit of the existing structural system is required, negatively impacting the cost–benefit of this retrofit approach. An example application is the 185 Berry St. building located in San Francisco, which was built in 1989 as a three‐story concrete moment frame, and had been retrofitted with two extra floors on top of an isolation system. Another example of early practical retrofit application, appearing in China, is a four‐story office building built in the 1950s, which was retrofit with four extra floors through inter‐story isolation …”

Section: Introductionmentioning

confidence: 99%

Shake table real‐time hybrid simulation techniques for the performance evaluation of buildings with inter‐story isolation

Zhang

Phillips

Taniguchi

et al. 2016

Struct. Control Health Monit.

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Summary Interstory isolation systems have recently gained popularity as an alternative for seismic protection, 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 reduced when compared to a conventional structural system. Furthermore, the base shear demand on the total structure is not significantly increased. Practical applications of inter‐story isolation have appeared in the United States, Japan, and China, and likewise new design validation techniques are needed to parallel growing interest. Real‐time hybrid simulation (RTHS) offers an alternative to investigate the performance of buildings with inter‐story isolation. Shake tables, standard equipment in many laboratories, are capable of providing the interface boundary conditions necessary for this application of RTHS. The substructure below the isolation layer can be simulated numerically while the superstructure above the isolation layer can be tested experimentally. This configuration provides a high‐fidelity representation of the nonlinearities in the isolation layer, including any supplemental damping devices. This research investigates the seismic performance of a 14‐story building with inter‐story isolation. A model‐based acceleration‐tracking approach is adopted to control the shake table, exhibiting good offline and online acceleration tracking performance. The proposed methods demonstrate that RTHS is an accurate and reliable means to investigate buildings with inter‐story isolation, including new configurations and supplemental control approaches.

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“…Mid-story isolation, which divides the building into two parts at an isolation interface layer located somewhere above the first floor, has been employed as a solution for adding additional stories to an existing structure without significantly increasing the lateral force demands in the existing structure *Correspondence to: Tracy C. Becker, Department of Civil Engineering, McMaster University, Hamilton, Canada. (Dutta et al, 2008). It is also used for new construction as a system to reduce structural demands and facilitate the transition between two structural systems (Tsuneki et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Enhanced performance through a dual isolation seismic protection system

Becker

Ezazi

2015

Struct. Design Tall Spec. Build.

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While base isolation successfully decreases the accelerations transmitted to a structure, a tradeoff is large unfavorable displacements in the isolation layer. This study investigates an innovative system, termed 'dual isolation', which applies two layers of isolation at the base and at mid-story to resolve this issue. A linear analytical solution for the equation of motion of the proposed system is developed on the basis of linear isolation theory. This creates a foundation to assess the behavior of various types of seismic protection systems and to select the damping and mass ratio that optimizes the performance of the proposed method. Dynamic response of an example dual isolated system to selected suites of ground motions is then examined. In addition to decreasing the displacement of the first isolation layer, the dual isolation system can greatly decrease floor accelerations of the upper portion of the building, further protecting building components and enhancing the comfort and safety of residents. displacement of the second floor, and when T 2 approaches T 1 , the mode shapes are approach 1 1 ! , and 1 À1 ! reduces the roof displacement of the system. This positive effect of increased mass ratio on the behavior of TMDs has been shown in other studies (Hoang et al., 2008;Taniguchi et al., 2008). Dual isolation systemFrom the examination of the theoretical results of mid-story isolation and base isolation with TMD, it is seen that the displacement demands on the second DOF decrease with larger values of γ and increase with larger T 2 , while the increase in T 2 reduces the displacement demand of the first DOF. These insights are used to select the preliminary parameters for the proposed dual isolation system. The same two DOF model shown in Figure 1 is used for a numerical response spectrum study. As a starting point, the mass ratio γ of the dual isolation system is chosen as 0.5, locating the second isolation layer at the mid height of the building. The period of the first isolation layer, T 1 , is chosen as 3.5 s, and the damping ratio of the first and second DOFs, β 1 and β 2 , were chosen as 15%. This dual isolation system was then analyzed using response spectrum analysis for a design basis earthquake (DBE), the spectrum for which is shown in Figure 2. The spectrum is defined for 10% probability of exceedance in 50 years downtown Seattle, WA, USA (47.60, À122.34), and soil type D (ASCE 07, 2010). The lateral story drifts found are presented in Figure 3, varying the period of the second isolation layer, T 2 . The left side of the graph represents the traditional base isolation system in which the natural period of the first DOF is much longer than the second DOF. As the period of the second DOF increases, the drift of the first DOF is reduced with the concession of increased drifts in the second DOF. This finding is in line with the theory explored in the previous section. Compared with the classic base isolation system, the participation factor of the first mode is decreased, reducing the first DOF's d...

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An Innovative Application of Base Isolation Technology

Cited by 7 publications

References 0 publications

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

Shake table real‐time hybrid simulation techniques for the performance evaluation of buildings with inter‐story isolation

Enhanced performance through a dual isolation seismic protection system

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