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Performance of tuned mass dampers against near-field earthquakes

  • Matta, E.
    • Structural Engineering and Mechanics
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    • v.39 no.5
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    • pp.621-642
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    • 2011
  • Passive tuned mass dampers (TMDs) efficiently suppress vibrations induced by quasi-stationary dynamic inputs, such as winds, sea waves or traffic loads, but may prove of little use against pulse-like excitations, such as near-field (NF) ground motions. The extent of such impairment is however controversial, partly due to the different evaluation criteria adopted within the literature, partly to the limited number of seismic records used in most investigations. In this study, three classical techniques and two new variants for designing a TMD on an SDOF structure are tested under 338 NF records from the PEER NGA database, including 156 records with forward-directivity features. Percentile response reduction spectra are introduced to statistically assess TMD performance, and TMD robustness is verified through Monte Carlo simulations. The methodology is extended to a variety of MDOF bending-type and shear-type frames, and simulated on a case study building structure recently constructed in Central Italy.Results offer an interesting insight into the performance of TMDs against NF earthquakes, ultimately showing that, if properly designed and sufficiently massive, TMDs are effective and robust even in the face of pulse-like ground motions. The two newly proposed design techniques are shown to generally outperform the classical ones.

Design of Friction Dampers installed at a Multi-Story Building under Seismic Load (지진하중을 받는 다층 건물에 설치된 마찰감쇠기 설계)

  • Seong, Ji-Young;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.4
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    • pp.457-462
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    • 2011
  • In this study, a simplified design procedure for friction dampers of a multi-story structure in order to reduce seismic response is proposed. To get insight for control effect of the structure with friction dampers is difficult, because of a nonlinear characteristic by a friction damper. Since a control force of a friction damper is influenced by coupling velocity between floors, adjoining modes are coupled. Thus structural response are derived by assuming steady-state response in resonance. As it is impossible that an exact solution is obtained for seismic load, first, a closed form solution can be achieved under harmonic vibration. Second, to convert a three-story building into a single-degree-of-freedom(SDOF) structure, modal analysis is performed. Third, an equivalent damping ratio is derived with utilizing closed form solution. And response reducing factor is proposed by it. Finally, friction force of a damper is designed for using response reducing factor, and then designed dampers are verified for seven seismic data. The nonlinear analysis results confirm the validity of the proposed procedure.

Equivalent Viscous Damping Ratio of a Friction Damper Installed in a SDOF Building (단자유도 건물에 설치된 마찰감쇠기의 등가점성감쇠비)

  • Seong, Ji-Young;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.2
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    • pp.199-208
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    • 2010
  • A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

Generation of Floor Response Spectra including Equipment-Structure Interaction in Frequency Domain (진동수 영역에서 기기-구조물 상호작용을 고려한 층응답스펙트럼의 작성)

  • Choi, Dong-Ho;Lee, Sang-Hoon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.6
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    • pp.13-19
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    • 2005
  • Floor response spectra for dynamic response of subsystem such as equipment, or piping in nuclear power plants are usually generated without considering dynamic interaction between main structure and subsystem. This study describes the analytic method in which equipment response spectra can be obtained through dynamic analysis considering equipment-structure Interaction(ESI). In this method, dynamic response of the equipment by this method is based on a dynamic substructure method in which the equipment-structure system is partitioned into the single-degree-ol-freedom system(SDOF) representing the equipment and the equipment support impedance representing the dynamic charactenstics of the structure ai the equipment support. A family of equipment response spectra is developed by applying this method to calculate the maximum responses of a family of SDOF equipment systems with wide banded equipment frequency, damping ratio, and mass. The method is validated by comparing the floor response spectrum from this method with the floor response spectrum generated from the rigorous analysis including equipments on the containment building of a prototypical nuclear power plant. in order to Investigate ESI effect in the response of equipment, response values from the method and the conventional approach without considering ESI are compared for the equipment having the mass less than 1% of the total structural mass. Response spectra from the method showed lower spectral amplitudes than those of the conventional floor response spectra around controlling frequencies.

Experimental Verification of a Liquid Damper with Changeable Natural Frequency for Building Response Control (고유진동수 조절이 가능한 액체댐퍼의 건물응답 제어실험)

  • Kim, Dong-Ik;Min, Kyung-Won;Park, Ji-Hun;Kim, Jae-Keon;Hwang, Kyu-Seok;Gil, Yong-Sik
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.4
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    • pp.323-330
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    • 2012
  • This study deals with the experiments of liquid dampers with multi cells whose vertical tubes are divided into several square columns for easily changing natural frequencies. Shaking table test is performed to verify control effectiveness of the dampers which are installed on a building structure. To design liquid dampers, a 64-story building structure is reduced to a SDOF structure with 1/20 of similitude laws based on acceleration. The structure model is made up to adjust its mass and stiffness easily, with separate mass and drive parts. Mass parts indicate real structure's weights and drive parts indicate real structure's stiffness with springs and LM guides. Manufactured liquid damper has 18 cells and its natural frequency ranges are 0.65Hz to 0.81Hz. Shaking table test is carried out with one way excitation to compare with only accelerations of a large-scale structure and a structure installed with liquid dampers. Control performance of the liquid damper is expressed by the transfer function from shaking table accelerations to the large-scale structure ones. Testing results show that the liquid damper reduced a large-scale structure's response by tuned natural frequencies.

Ground Vibration Test for Korea Sounding Rocket - III (KSR-III의 전기체 모달 시험)

  • 우성현;김영기;이동우;문남진;김홍배
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.441-447
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    • 2002
  • KSR-III(Korea Sounding Rocket - III), which is being developed by Space Technology R&D Division of KARI(Korea Aerospace Research Institute) will be launched in late 2002. It is a three-stage, liquid propellant rocket which can reach 250 km altitude and will carry out observation of ozone layer and scientific experiments, such as microgravity experiment, and atmospheric measurement. KSR-III is believed to be an intermediate to the launch vehicle capable of carrying a satellite to its orbit. Space Test Department of KARI performed GVT(Ground Vibration Test) fer KSR-III EM at Rocket Test Building of KARI. GVT is very important for predicting the behavior of rocket in its operation, developing flight control program and performing aerodynamic analysis. This paper gives an introduction of rocket GVT configuration and information on test procedures, techniques and results of It. In this test. to simulate free-free condition, test object hung in the air laterally by 4 bungee cords specially devised. For the excitation of test object, pure random signal by two electromagnetic shakers was used and total 22 frequency response functions were achieved. Polyreference parameter estimation was performed to identify the modal parameters with MIMO(Multi-Input-Multi-Output) method. As the result of the test, low frequency mode shapes and modal parameters below 60Hz were identified

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Effect of Seismic Design Details in Reinforced Concrete Beams on Blast-Resistance Performance (철근콘크리트 보의 내진 설계 상세가 폭발 저항 성능에 미치는 영향)

  • Kim, Kuk-Jae;Kim, Han-Soo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.5
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    • pp.427-434
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    • 2017
  • Recently, awareness of the public about the explosion damage has increased due to the increased risk of terrorism. The criteria for blast-resistance design is not sufficient in Korea, it is necessary to develop blast-resistance design for the stability and safety of building by static analysis of current blast-resistance design. In addition, as the increase of earthquake occurrence necessitates the seismic design, it is studied to judge the blast-resistance performance of members applying seismic design without blast-resistance design. Currently, the general analysis of blast load is to refer to UFC 3-340-02 manual. Blast-resistance performance was studied by applying characteristics of blast load through UFC 3-340-02 manual, beam converted into equivalent SDOF System. It is proved that blast-resistance performance is improved when seismic detail is applied considering the maximum deflection of normal, intermediate, and special moment frames.

Nonlinear Response Spectra of Artificial Earthquake Waves Compatible with Design Spectrum (설계용 스펙트럼에 적합한 인공지진파에 의한 비선형 응답 특성의 분석)

  • Jun, Dae-Han;Kang, Pyeong-Doo;Kim, Jae-Ung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.5
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    • pp.63-71
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    • 2006
  • In seismic response analysis of building structures, the input ground accelerations have considerable effect on the nonlinear response characteristics of structures. The characteristics of soil and the locality of the site where those ground motions were recorded affect on the contents of earthquake waves. Therefore, it is difficult to select appropriate input ground motions for seismic response analysis. This study describes a generation of artificial earthquake wave compatible with seismic design spectrum, and also evaluates the nonlinear response spectra by the simulated earthquake motions. The artificial earthquake wave are generated according to the previously recorded earthquake waves in past earthquake events. The artificial wave have identical phase angles to the recorded earthquake wave, and their overall response spectra are compatible with seismic design spectrum with 5% critical viscous damping. Each simulated earthquake wave has a identical phase angles to the original recorded ground acceleration, and match to design spectra in the range of period from 0.02 to 10.0 seconds. The seismic response analysis is performed to examine the nonlinear response characteristics of SDOF system subjected to the simulated earthquake waves. It was concluded that the artificial earthquake waves simulated in this paper are applicable as input ground motions for a seismic response analysis of building structures.

The Vibration Comfort Evaluation of the Shaking Table Mass Foundation (진동대 반력기초의 진동사용성 평가)

  • Choi, Hyoung-Suk;Jung, Da-Jung;Kim, Seong-Do;Cheung, Jin-Hwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.15 no.2
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    • pp.53-60
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    • 2011
  • When designing building structures, dynamic serviceability is one of the most important items. Much research is being carried out on machine vibrations that affect inside residents and expensive equipment in the building structure. The vibration effect generally depends on the mass ratio, and an adequate mass ratio is determined by comparison with the serviceability limit according to the criteria. This study investigates the evaluation of vibration serviceability by using ISO 2631 to confirm the propriety of adequate mass ratios and it is verified that the application of a complicated FE model to model the real large shaking table facility with the mathematical model simulated as a SDOF system. The weighted RMS value is then compared with the comfort limit given by ISO 2631. As a result, the analysis of the numerical model is consistent with analysis of the FE model. Moreover, it is found that the adequate mass ratio of the concrete foundation and shake table, considering the self-weight of the real facility, should be less than 0.013. It is also confirm that the sample facility is satisfies the requirement of an adequate mass ratio.

Evaluation of the Inelastic Seismic Response of Curved Bridges by Capacity Spectrum Method using Equivalent Damping (등가감쇠비를 이용한 역량스펙트럼법에 의한 곡선교의 비탄성지진응답 평가)

  • Joe, Yang-Hee;Cho, Sung-Gook;Ma, Jeong-Suck
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.1
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    • pp.17-26
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    • 2009
  • The capacity spectrum method (CSM), which is known to be an approximate technique for assessing the seismic capacity of an existing structure, was originally proposed for simple building structures that could be modeled as single-degree-of-freedom (SDOF) systems. More recently, however, CSM has increasingly been adopted for assessing most bridge structures, as it has many practical advantages. Some studies on this topic are now being performed, and a few results of these have been presented as ground-breaking research. However, studies have until now been limited to symmetrical straight bridges only. This study evaluates the practical applicability of CSM to the evaluation of irregular curved bridges. For this purpose, the seismic capacities of 3-span prestressed concrete bridges with different subtended angles subjected to some recorded earthquakes are compared with a more refined approach based on nonlinear time history analysis. The results of the study show that when used for curved bridges, CSM induces higher inelastic displacement responses than the actual values, and that the gap between the two becomes larger as the subtended angle increases.