• Title/Summary/Keyword: Performance isolation

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Seismic performance of a resilient low-damage base isolation system under combined vertical and horizontal excitations

  • Farsangi, Ehsan Noroozinejad;Tasnimi, Abbas Ali;Yang, T.Y.;Takewaki, Izuru;Mohammadhasani, Mohammad
    • Smart Structures and Systems
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    • v.22 no.4
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    • pp.383-397
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    • 2018
  • Traditional base isolation systems focus on isolating the seismic response of a structure in the horizontal direction. However, in regions where the vertical earthquake excitation is significant (such as near-fault region), a traditional base-isolated building exhibits a significant vertical vibration. To eliminate this shortcoming, a rocking-isolated system named Telescopic Column (TC) is proposed in this paper. Detailed rocking and isolation mechanism of the TC system is presented. The seismic performance of the TC is compared with the traditional elastomeric bearing (EB) and friction pendulum (FP) base-isolated systems. A 4-storey reinforced concrete moment-resisting frame (RC-MRF) is selected as the reference superstructure. The seismic response of the reference superstructure in terms of column axial forces, base shears, floor accelerations, inter-storey drift ratios (IDR) and collapse margin ratios (CMRs) are evaluated using OpenSees. The results of the nonlinear dynamic analysis subjected to multi-directional earthquake excitations show that the superstructure equipped with the newly proposed TC is more resilient and exhibits a superior response with higher margin of safety against collapse when compared with the same superstructure with the traditional base-isolation (BI) system.

Response of Base Isolation System Subjected to Spectrum Matched Input Ground Motions (스펙트럼 적합 입력지반운동에 의한 면진구조의 응답 특성)

  • Kim, Jung Han;Kim, Min Kyu;Choi, In-Kil
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.2
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    • pp.89-95
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    • 2013
  • Structures in a nuclear power system are designed to be elastic even under an earthquake excitation. However a structural component such as an isolator shows inelastic behavior inherently. For the seismic assessment of nonlinear structures, response history analysis should be performed. In this study, the response of base isolation system was analyzed by response history analysis for the seismic performance assessment. Firstly, several seismic assessment criteria for a nuclear power plant structure were reviewed for the nonlinear response history analysis. Based on these criteria, the spectrum matched ground motion generation method modifying a seed earthquake ground motion time history was adjusted. Using these spectrum matched accelerograms, the distribution of displacement responses of the simplified base isolation system was evaluated. The resulting seismic responses excited by the modified ground motion time histories and the synthesized time history generated by stochastic approach were compared. And the response analysis of the base isolation system considering the different intensities in each orthogonal direction was performed.

Evaluation of Floor Impact Sound Isolation in a Dry Floor System (건식 바닥구조의 바닥충격음 차단성능 평가)

  • You, Jin;Ryu, Jong-Kwan;Jeon, Jin-Young;Lee, Chung-Hwa;Kim, Chul-Hwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.950-953
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    • 2005
  • Floor impact sounds from two different floor systems were measured. One of the two floor systems is a dry floor system (with 150mm concrete slab) and the other is a standard floor system (210mm concrete slab). Real impact sources such as jumping and running of children were used as well as standard impact sources (bang machine, impact ball and tapping machine) to evaluate sound Isolation of the two floor systems. Subjective evaluations of the floor impact sound isolation performance for the two systems were also conducted by the methods of 3 scales & 9 categories, paired comparison and semantic differentials. Measurement results indicate that floor impact sound isolation performance of the dry floor was better than that of standard floor in both cases of real and standard impact sources. The subjects in auditory experiments also evaluated the dry floor as a better sound isolation system.

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Wavelet analysis of soil-structure interaction effects on seismic responses of base-isolated nuclear power plants

  • Ali, Shafayat Bin;Kim, Dookie
    • Earthquakes and Structures
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    • v.13 no.6
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    • pp.561-572
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    • 2017
  • Seismic base isolation has been accepted as one of the most popular design procedures to protect important structures against earthquakes. However, due to lack of information and experimental data the application of base isolation is quite limited to nuclear power plant (NPP) industry. Moreover, the effects of inelastic behavior of soil beneath base-isolated NPP have raised questions to the effectiveness of isolation device. This study applies the wavelet analysis to investigate the effects of soil-structure interaction (SSI) on the seismic response of a base-isolated NPP structure. To evaluate the SSI effects, the NPP structure is modelled as a lumped mass stick model and combined with a soil model using the concept of cone models. The lead rubber bearing (LRB) base isolator is used to adopt the base isolation system. The shear wave velocity of soil is varied to reflect the real rock site conditions of structure. The comparison between seismic performance of isolated structure and non-isolated structure has drawn. The results show that the wavelet analysis proves to be an efficient tool to evaluate the SSI effects on the seismic response of base-isolated structure and the seismic performance of base-isolated NPP is not sensitive to the effects in this case.

Large strain nonlinear model of lead rubber bearings for beyond design basis earthquakes

  • Eem, Seunghyun;Hahm, Daegi
    • Nuclear Engineering and Technology
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    • v.51 no.2
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    • pp.600-606
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    • 2019
  • Studies on the application of the lead rubber bearing (LRB) isolation system to nuclear power plants are being carried out as one of the measures to improve seismic performance. Nuclear power plants with isolation systems require seismic probabilistic safety assessments, for which the seismic fragility of the structures, systems, and components needs be calculated, including for beyond design basis earthquakes. To this end, seismic response analyses are required, where it can be seen that the behaviors of the isolation system components govern the overall seismic response of an isolated plant. The numerical model of the LRB used in these seismic response analyses plays an important role, but in most cases, the extreme performance of the LRB has not been well studied. The current work therefore develops an extreme nonlinear numerical model that can express the seismic response of the LRB for beyond design basis earthquakes. A full-scale LRB was fabricated and dynamically tested with various input conditions, and test results confirmed that the developed numerical model better represents the behavior of the LRB over previous models. Subsequent seismic response analyses of isolated nuclear power plants using the model developed here are expected to provide more accurate results for seismic probabilistic safety assessments.

A Reconfigurable Directional Coupler Using a Variable Impedance Mismatch Reflector for High Isolation

  • Lee, Han Lim;Park, Dong-Hoon;Lee, Moon-Que
    • Journal of electromagnetic engineering and science
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    • v.16 no.4
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    • pp.206-209
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    • 2016
  • This letter proposes a reconfigurable directional coupler that uses a variable impedance mismatch reflector to achieve high isolation characteristics in the antenna front end. The reconfigurable coupler consists of a directional coupler and a single-pole four-throw (SP4T) switch with different load impedances as a variable load mismatch reflector. Selection of the load impedance by the reflector allows cancellation of the reflected signal due to antenna load mismatch and the leakage from the input to isolation port of the directional coupler, resulting in high isolation characteristics. The performance of the proposed architecture in separating the received (Rx) signal from the transmitted (Tx) signal in the antenna front end was verified by implementing and testing the reconfigurable coupler at 917 MHz for UHF radio-frequency identification (RFID) applications. The proposed reconfigurable directional coupler showed an improvement in the isolation characteristics of more than 20 dB at the operation frequency band.

Development of the Optimal Design Technique for the Pneumatic Vibration Isolation System by Nonlinear Modeling and Analysis (공압방진시스템의 비선형 모델링과 해석을 통한 최적설계기술 개발)

  • 문준희;박희재
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.151-154
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    • 2001
  • The pneumatic vibration isolation systems have been widely used in industry and laboratories, but the full mathematical analysis and nonlinear modeling techniques have not been reported yet, even while the nonlinear features of the pneumatic vibration isolation system decide the main characteristics. For instance, the orifice in a pneumatic vibration isolator has been traditionally considered as a simple viscous damper, which was too much simplified to explain the performance of the isolation system. In this paper, the nonlinear characteristics are considered for the orifice and chamber, etc. The numerical simulation is carried out by the MATLAB/Simulink software. From the analysis result, a clear trend of the nonlinear features is shown: the vibration transmissibility changes not only due to the excitation frequency but also due to the amplitude of the vibration excitation. Therefore various design parameters are optimally chosen for the vibration isolation system. The proposed methods show good compatibility between the analysis results and the experiments.

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Vibration control of the vibration isolation system using the electromagnetic actuator (전자석 액츄에이터에 의한 수동방진 테이블의 제어)

  • Choi, Hyun;Lee, Jung-Youn
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.227-232
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    • 2003
  • As the most precision equipment requiring very strict vibration environment are vulnerable to the surrounding vibration condition, they adapt the passive or active vibration isolation system. When it comes to the passive isolation system, the resonance of the isolation system causes excessive resonance response, and finally results in the degrade the equipment performance. This paper deals with the active control method to control this resonance induced response, and includes the experiment on the active control for controlling the resonance response on the table against the excitation of the same frequency with the natural frequency of the isolation system. The electromagnetic actuator was designed and the control effect was verified by the experiment. The experiment showed that the electromagnetic actuator is effective for controlling the low frequency isolation resonance response of the precision equipment.

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A Comparative Study on Aseimatic Performances of Various Base Isolation Systems (여러 가지 기초분리 장치의 내진성능에 관한 비교연구)

  • 박규식
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1999.10a
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    • pp.236-243
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    • 1999
  • A comparative study on aseismatic performances of various base isolation systems for the multi-span continuous bridge is carried out. Several leading base isolation systems the LRB system the RF system the R-FBI system and the EDF system are considered, The displacement of the deck the deformation of the upper ends of the piers the shear force and the bending moment of the lower ends of the piers are obtained by using the accelerograms of the N00W component of El Centro earthquake(1940) and the N90W component of Mexico City earthquake(1985) Nonlinear time-history analysis is carried out. comparisons of the results with the conventional bearing show that the base isolation systems are very effective in reducing the forces transmitted to the superstructures. Furthermore the results also show that the friction-type base isolation systems are less sensitive to unexpected variations in frequency content of the ground acceleration. The R-FBI system shows a good aseismatic performance comparing with other base isolation systems.

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Prediction of Long Term Performance and Creep of Laminated Natural Rubber Bearings(NRB) (적층 천연고무 면진장치의 장기성능과 크리프에 대한 예측)

  • Hwang, Kee Tae;Seo, Dae Won;Cho, Sung Gook
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.3
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    • pp.117-125
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    • 2013
  • Seismic isolation has been considered and utilized in various industries as a way to prevent huge damage on to structures by large earthquakes in various industries. The laminated Laminated rubber bearings is are most frequently used in seismic isolation systems. The structural Structural safety could not be assured unless the performance of the rubber bearing is not guaranteed for the life time of the structure under the consideration that the bearing is a critical structural member to sustain vertical loads in the seismically isolated structure. However, there are few studies on the deterioration problems of rubber bearings during their service life. The long term performance of the rubber bearings was not considered in past designs of seismically isolated structures. This study evaluates the long term performance and creep characteristics of laminated natural rubber bearings that are used in seismically isolated buildings. For the this study, a set of accelerated thermal aging tests and creep tests are were performed on real specimens. The experimental results show that the natural rubber bearings would have a stable change rate of change for durability under severe environmental conditions for a long time.