• Title, Summary, Keyword: acceleration response

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Generation of critical and compatible seismic ground acceleration time histories for high-tech facilities

  • Hong, X.J.;Xu, Y.L.
    • Structural Engineering and Mechanics
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    • v.26 no.6
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    • pp.687-707
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    • 2007
  • High-tech facilities engaged in the production of semiconductors and optical microscopes are extremely expensive, which may require time-domain analysis for seismic resistant design in consideration of the most critical directions of seismic ground motions. This paper presents a framework for generating three-dimensional critical seismic ground acceleration time histories compatible with the response spectra specified in seismic design codes. The most critical directions of seismic ground motions associated with the maximum response of a high-tech facility are first identified. A new numerical method is then proposed to derive the power spectrum density functions of ground accelerations which are compatible with the response spectra specified in seismic design codes in critical directions. The ground acceleration time histories for the high-tech facility along the structural axes are generated by applying the spectral representation method to the power spectrum density function matrix and then multiplied by envelope functions to consider nonstationarity of ground motions. The proposed framework is finally applied to a typical three-story high-tech facility, and the numerical results demonstrate the feasibility of the proposed approach.

Seismic response of non-structural components attached to reinforced concrete structures with different eccentricity ratios

  • Aldeka, Ayad B.;Dirar, Samir;Chan, Andrew H.C.;Martinez-Vazquez, Pedro
    • Earthquakes and Structures
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    • v.8 no.5
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    • pp.1069-1089
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    • 2015
  • This paper presents average numerical results of 2128 nonlinear dynamic finite element (FE) analyses of lightweight acceleration-sensitive non-structural components (NSCs) attached to the floors of one-bay three-storey reinforced concrete (RC) primary structures (P-structures) with different eccentricity ratios. The investigated parameters include the NSC to P-structure vibration period ratio, peak ground acceleration, P-structure eccentricity ratio, and NSC damping ratio. Appropriate constitutive relationships were used to model the behaviour of the RC P-structures. The NSCs were modelled as vertical cantilevers fixed at their bases with masses on the free ends and varying lengths so as to match the vibration periods of the P-structures. Full dynamic interaction was considered between the NSCs and P-structures. A set of seven natural bi-directional ground motions were used to evaluate the seismic response of the NSCs. The numerical results show that the acceleration response of the NSCs depends on the investigated parameters. The accelerations of the NSCs attached to the flexible sides of the P-structures increased with the increase in peak ground acceleration and P-structure eccentricity ratio but decreased with the increase in NSC damping ratio. Comparison between the FE results and Eurocode 8 (EC8) predictions suggests that, under tuned conditions, EC8 provisions underestimate the seismic response of the NSCs mounted on the flexible sides of the plan-irregular RC P-structures.

Linear and nonlinear site response analyses to determine dynamic soil properties of Kirikkale

  • Sonmezer, Yetis Bulent;Bas, Selcuk;Isik, Nihat Sinan;Akbas, Sami Oguzhan
    • Geomechanics and Engineering
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    • v.16 no.4
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    • pp.435-448
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    • 2018
  • In order to make reliable earthquake-resistant design of civil engineering structures, one of the most important considerations in a region with high seismicity is to pay attention to the local soil condition of regions. It is aimed in the current study at specifying dynamic soil characteristics of Kirikkale city center conducting the 1-D equivalent linear and non-linear site response analyses. Due to high vulnerability and seismicity of the city center of Kirikkale surrounded by active many faults, such as the North Anatolian Fault (NAF), the city of Kirikkale is classified as highly earthquake-prone city. The first effort to determine critical site response parameter is to perform the seismic hazard analyses of the region through the earthquake record catalogues. The moment magnitude of the city center is obtained as $M_w=7.0$ according to the recorded probability of exceedance of 10% in the last 50 years. Using the data from site tests, the 1-D equivalent linear (EL) and nonlinear site response analyses (NL) are performed with respect to the shear modulus reduction and damping ratio models proposed in literature. The important engineering parameters of the amplification ratio, predominant site period, peak ground acceleration (PGA) and spectral acceleration values are predicted. Except for the periods between the period of T=0.2-1.0 s, the results from the NL are obtained to be similar to the EL results. Lower spectral acceleration values are estimated in the locations of the city where the higher amplification ratio is attained or vice-versa. Construction of high-rise buildings with modal periods higher than T=1.0 s are obtained to be suitable for the city of Kirikkale. The buildings at the city center are recommended to be assessed with street survey rapid structural evaluation methods so as to mitigate seismic damages. The obtained contour maps in this study are estimated to be effective for visually characterizing the city in terms of the considered parameters.

Acceleration Feedforward Control in Active Magnetic Bearing System Subject to Base Motion by Filtered-x LMS Algorithm (베이스 가진을 받는 능동자기베어링 시스템에서 Filtered-x LMS 알고리듬을 이용한 가속도 앞먹임 제어)

  • Kang, Min-Sig
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.10
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    • pp.1712-1719
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    • 2003
  • This paper concerns on application of active magnetic bearing(AMB) system to levitate the elevation axis of an electro-optical sight mounted on moving vehicles. In such a system, it is desirable to retain the elevation axis within the predetermined air-gap while the vehicle is moving. An optimal base acceleration feedforward control is proposed to reduce the base motion response. In the consideration of the uncertainty of the system model, a filtered-x least-mean-square(FXLMS) algorithm is used to estimate the frequency response function of the feedforward control which cancels base motions. The frequency response function is fitted to an optimal feedforward control. Experimental results demonstrate that the proposed control reduces the air-gap deviation to 27.7% that by feedback control alone.

Seismic Response Analysis of a Base-Isolated Structure Supported on High Damping Rubber Bearings (고감쇠 면진베어링에 의해 지지된 면진구조물의 지진응답해석)

  • Yoo, Bong;Lee, Jae-Han;Koo, Gyeong-Hoi
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.99-106
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    • 1995
  • The seismic responses of a base Isolated Pressurized Water Reactor(PWR) are investigated using a mathematical model which expresses the superstructure as a linear lumped mass-spring and the seismic Isolator as an equivalent spring-damper. Time history analyses are performed for the 1940 El Centre earthquake with linear amplification. In the analysis 5% of structural damping is used for the superstructure. The effects of high damping rubber bearing on seismic response of the superstructure in base isolated system are evaluated for four stiffness model types. The acceleration responses in base isolated PWR superstructure with high damping rubber bearings are much smaller than those in fixed base structure. In the higher strain region where stiffness behaves non-linearly, the acceleration responses modelled by one equivalent stiffness are smaller than those in nonlinear spring model, and the higher stiffness spring model of isolator exhibits larger peak acceleration response at superstructure in the frequency range above 2.0 Hz. when subjected to linearly amplified 1940 El Centre earthquake.

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Response of a prototype brain material subjected to rotational acceleration (회전가속에 대한 프로토타입 뇌재료의 반응)

  • Lee, E. S.
    • Journal of the korean Society of Automotive Engineers
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    • v.11 no.5
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    • pp.76-89
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    • 1989
  • With the objective of studying the response of brain tissue in a transient rotational acceleration of the head, as occurs in car crash, the problem of a cylindrical case containing a prototype brain material of silicone gel and subjected to a rotational acceleration around the axis of the cylinder is analysed. The prototype material is considered to be homogeneous and isotropic, and is modeled alternatively as a linear elastic or a linear viscoelastic solid. The computational model for the present problem consists of a 3-dimensional isoparametric finite element model, wherein large deformations and large strains are treated through the updated Lagrangian approach. A comparison of the results of the present 3-dimensional computations, with the attendant assumptions on material data, is made with the results of independent experimental study. The deformation profiles and the major characteristics of response of the brain material are in good agreement with the test results. Moreover, the study suggests the possibility that the use of more accurate material data may yield very useful results even appropriate for accurate quantification of deformations.

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A Simulation for the Impact Response Analysis of a Motor Cycle Helmet (시뮬레이션에 의한 오토바이 헬멧의 충격 응답 분석)

  • 최명진
    • Journal of the Korea Society for Simulation
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    • v.8 no.4
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    • pp.25-31
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    • 1999
  • To analyze the impulsive response of a motorcycle helmet, a simulation is performed using the finite element method. Based upon the simulation result, an equivalent one degree of freedom vibrational system is adapted, and transient impulsive responses are analysed to investigate the influence of engineering parameters such as damping, natural frequency, and impact velocity on the impulsive response of the helmet. Maximum gravitational acceleration reduces as the damping factor value increases. When the damping factor value is around 0.6 or larger, the maximum acceleration does not change. With respect to the natural frequency and the impact velocity, it increases linearly. The relationship between head injury criterion(HIC) and maximum gravitational acceleration is also presented. The scheme of this study is expected to be utilized to economize the design process of high quality motorcycle helmets.

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Optimum Manufacturing Condition of Side Wall End Milling Using Response Surface Methodology (측벽 엔드밀 가공 시 반응표면법을 이용한 최적가공조건)

  • Choi, Jae-Gi;Park, Jin-Woo;Hong, Do-Kwan;Woo, Byung-Chul;Ahn, Chan-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1313-1317
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    • 2007
  • Manufacturing condition is one of the most important factors in precision manufacturing. In this study, we optimized minimizing the Z vibration acceleration using RSM(response surface methodology) by table of orthogonal array. RSM was well adapted to make the analytical model of the minimum vibration acceleration and enable the objective function to be easily created and a great deal of the time in computation to be saved. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of manufacture condition.

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Generation of artificial earthquake time histories for the seismic analysis of base-isolated bridges (지진격리교량의 지진해석을 위한 인공지진파의 작성)

  • Kim, Nam-Sik;Kim, Jae-Min;Lee, Gye-Hee;Kang, Hyeong-Taek
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.487-494
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    • 2005
  • In this study, a set of artificial earthquake time histories, which can be used for the earthquake-resistant design of seismically isolated highway bridges, was presented. In addition, adequateness of the generated ground accelerations was investigated. These were performed based on the seismic design standard for seismically isolated bridges. Total of 22 acceleration time histories were generated for each soil condition by the spectral method. The time histories were verified to meet the code provisions including (1) mean response spectrum at control frequencies, (2) EPGA (effective peak ground acceleration), and (3) correlation coefficient. Finally, the maximum response corresponding to four time histories and the mean response associated with seven time histories were computed using the generated acceleration time histories, which shows validity of the proposed artificial earthquake time histories.

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Using Numerical Solutions of the Vibration Measurement Accelerometers attached Vibration Isolator (수치 해법을 이용하여 제진대에 부착된 가속도 센서의 진동 측정)

  • Shin, Dong-Ho;Lee, Jung-Woo;Lee, Jong-Won;Oh, Jae-Eung;Lee, Jung-Youn
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.875-880
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    • 2012
  • According to the fixation detailed drawing and lightweight anger tendency of the product the vibration control of precision equipments is essential and establishes under the equipments. so It is important to know vibration characteristics of vibration isolator. For this reason the accelerometer attaches in vibration isolator and measures an acceleration response. The acceleration response which is measured will lead double integral and will be able to predict a displacement of vibration isolator. However, in compliance with the effect of the accelerometer can not be accurately. From this paper, mass, damping ratio and natural frequency of the accelerometers by changing the vibration isolator to predict the acceleration response and the results were compared.

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