• Title/Summary/Keyword: earthquake excitation

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Equivalent Damping Ratio Based on Earthquake Characteristics of a SDOF Structure with an MR Damper (지진특성에 따른 MR감쇠기가 설치된 단자유도 구조물의 등가감쇠비)

  • Moon, Byoung-Wook;Park, Ji-Hun;Lee, Sung-Kyung;Min, Kyung-Won
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.1
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    • pp.87-93
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    • 2008
  • Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

Seismic Behavior of the Friction Pendulum System in Bridge Seismic Isolation (교량에 설치된 마찰 단진자 시스템의 지진하중에 의한 거동연구)

  • 오순택;김영석;김연택
    • Journal of the Earthquake Engineering Society of Korea
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    • v.2 no.2
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    • pp.13-22
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    • 1998
  • This paper summarizes a study on the application of the friction pendulum system in bridge seismic isolation. Shaking table tests have been carried out on a model structure isolated with F.P.S and the obtained structural responses are compared to those of non-isolated. It can be concluded the F.P.S increases the earthquake resistance capacity of the isolated structure. It is also found that the stiffness of bearing, being controlled by the radius of curvature of the spherical sliding interface, is unaffected by the amplitude of the input excitation. Furthermore, the coefficient of sliding friction is velocity dependent so that in weak excitation the sliding velocity is low and, accordingly, the mobilized friction force is less than the one mobilized in strong excitation. Also, the frictional properties of the bearings remain markedly stable after extensive testing, and the permanent displacements are small and not cumulative in successive earthquakes.

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Comparison Between Performance of Wireless MEMS Sensors and an ICP Sensor With Earthquake-Input Ground Motions (지진 입력 진동대를 이용한 무선 MEMS 센서와 ICP 가속도계의 성능 비교)

  • Mapungwana, S.T.;Lee, Jong-Ho;Yoon, Sung-Won
    • Journal of Korean Association for Spatial Structures
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    • v.19 no.2
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    • pp.63-72
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    • 2019
  • Wireless sensors are more favorable in measuring structural response compared to conventional sensors in terms of them being easier to use with no issues with cables and them being considerably cheaper. Previous tests have been conducted to analyze the performance of MEMS (Micro Electro Mechanical Systems) sensor in sinusoidal excitation tests. This paper analyzes the performance of in-built MEMS sensors in devices by comparing with an ICP sensor as the reference. Earthquake input amplitude excitation in shaking table tests was done. Results show that MEMS sensors are more accurate in measuring higher input amplitude measurements which range from 100gal to 250gal than at lower input amplitudes which range from 10gal to 50gal. This confirms the results obtained in previous sinusoidal tests. It was also seen that natural frequency results have lower error values which range from 0% to 3.92% in comparison to the response spectra results. This also confirms that in-built MEMS sensors in mobile devices are good at estimating natural frequency of structures. In addition, it was also seen that earthquake input amplitudes with more frequency contents (Gyeongju) had considerably higher error values than Pohang excitation tests which has less frequency contents.

Seismic Response Control of Dome Structure Subjected to Multi-Support Earthquake Excitation (다중지점 지진하중을 받는 돔 구조물의 지진응답 제어)

  • Kim, Gee-Cheol;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.14 no.4
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    • pp.89-96
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    • 2014
  • Spatial structures as like dome structure have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and effectively control of seismic response of spatial structure subjected to multi-supported excitation. In this study, star dome structure that is subjected to multi-supported excitation was used as an example spatial structure. The response of the star dome structure under multiple support excitation are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. And the application of passive tuned mass damper(TMD) to seismic response control of star dome structures has been investigated. From this numerical analysis, it is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation. And it is reasonable to install TMD to the dominant points of each mode. And it is found that the passive TMD could effectively reduce the seismic responses of dome structure subjected to multi-supported excitation.

Seismic Response of Base-Isolated Bridge for Soil Types (지반조건에 대한 면진교량의 지진응답 비교)

  • 성낙구
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.10a
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    • pp.455-462
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    • 2000
  • In this study seismic response of a base-isolated bridge for soil types is compared. Bilinear model is used for lead rubber bearing(LRB). Accelerograms whose response spectrum matches the design spectrum for soil types are used as earthquake ground excitation. Nonlinear time history analyses using the SAP2000 program is performed. The results show that seismic response of a base-isolated bridge is increased as the soil becomes soft.

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ANALYSIS OF SLIDING MOTION OF PILED MULTI-BLOCK SYSTEMS CONSIDERING HORIZONTAL ROTATION (적층 강체블록의 수직축 회전을 고려한 Sliding운동 해석과 실험)

  • 황인섭;김재관
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.03a
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    • pp.193-199
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    • 2003
  • The most cultural heritages are composed of piled multi-block systems which are vulnerable to earthquakes. The stone of low height tends to slide when the excitation such as earthquake is applied and this sliding motion has effects on the whole response of the structure. In this study, analytical method of sliding motion of the piled multi-block systems considering horizontal rotation is developed and compared with shaking table test results. It is shown that the nonlinear analysis of sliding motion of multi-block system leads to satisfactory results.

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Combinatorial continuous non-stationary critical excitation in M.D.O.F structures using multi-peak envelope functions

  • Ghasemi, S. Hooman;Ashtari, P.
    • Earthquakes and Structures
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    • v.7 no.6
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    • pp.895-908
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    • 2014
  • The main objective of critical excitation methods is to reveal the worst possible response of structures. This goal is accomplished by considering the uncertainties of ground motion, which is subjected to the appropriate constraints, such as earthquake power and intensity limit. The concentration of this current study is on the theoretical optimization aspect, as is the case with the majority of conventional critical excitation methods. However, these previous studies on critical excitation lead to a discontinuous power spectral density (PSD). This paper introduces some critical excitations which contain proper continuity in frequency domain. The main idea for generating such continuous excitations stems from the combination of two continuous functions. On the other hand, in order to provide a non-stationary model, this paper attempts to present an appropriate envelope function, which unlike the previous envelope functions, can properly cover the natural earthquakes' accelerograms based on multi-peak conditions. Finally, the proposed method is developed into the multiple-degree-of-freedom (M.D.O.F) structures.

Seismic Response of Arch Structure Subjected to Different Ground Motion (상이한 지반조건을 갖는 아치구조물의 지진응답 분석)

  • Kim, Gee-Cheol;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.13 no.1
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    • pp.113-119
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    • 2013
  • Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response of spatial structure for seismic design of spatial structure. An arch structure is used as an example structure because it has primary characteristics of spatial structures. Multiple support excitation may be subjected to supports of a spatial structure because ground condition of spatial structures is different. In this study, the response analysis of the arch structure under multiple support excitation and simple support excitation is studied. By means of the pseudo excitation method, the seismic response is analyzed for long span spatial structure. It shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic response of spatial structure under multiple support excitation and simple support excitation are the different in some case. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation because the spatial structure supports may be different.

Effect of excitation intensity on slope stability assessed by a simplified approach

  • Korzec, Aleksandra;Jankowski, Robert
    • Earthquakes and Structures
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    • v.21 no.6
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    • pp.601-612
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    • 2021
  • The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

Optimum control system for earthquake-excited building structures with minimal number of actuators and sensors

  • He, Jia;Xu, You-Lin;Zhang, Chao-Dong;Zhang, Xiao-Hua
    • Smart Structures and Systems
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    • v.16 no.6
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    • pp.981-1002
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    • 2015
  • For vibration control of civil structures, especially large civil structures, one of the important issues is how to place a minimal number of actuators and sensors at their respective optimal locations to achieve the predetermined control performance. In this paper, a methodology is presented for the determination of the minimal number and optimal location of actuators and sensors for vibration control of building structures under earthquake excitation. In the proposed methodology, the number and location of the actuators are first determined in terms of the sequence of performance index increments and the predetermined control performance. A multi-scale response reconstruction method is then extended to the controlled building structure for the determination of the minimal number and optimal placement of sensors with the objective that the reconstructed structural responses can be used as feedbacks for the vibration control while the predetermined control performance can be maintained. The feasibility and accuracy of the proposed methodology are finally investigated numerically through a 20-story shear building structure under the El-Centro ground excitation and the Kobe ground excitation. The numerical results show that with the limited number of sensors and actuators at their optimal locations, the predetermined control performance of the building structure can be achieved.