• Title/Summary/Keyword: earthquake motion

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Earthquake Analaysis of Cylindrical Liquid Storage tanks Considering Effects of Soil-Structure Interaction (지반-구조물 상호작용을 고려한 원통형 유체저장탱크의 지진해석)

  • 김재민
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1999.10a
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    • pp.83-90
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    • 1999
  • This paper presents a method of seismic analysis for a cylindrical liquid storage structure on horizontally layered half-space considering the effects of the interior fluid and exterior soil medium in the frequency domain. the horizontal and rocking motions of the structures are included in this study. The fluid motion is expressed in terms of analytical velocity potential function which can be obtained by solving the boundary value problem including the sloshing behavior of the fluid as well as deformed configuration of the structure. The effect of the fluid is included in the equation of motion as the impulsive added mass and a frequency-dependent convective added mass along the nodes on the wetted boundary with structure. The soil medium is presented using the 3-D axisymmetric finite elements and dynamic infinite elements. The present method can be applied to the structures embedded in ground as well as on ground since it models the soil medium directly as well as the structure. For the purpose of vertification dynamci characteristics of a tank on homogeneous half-space is analyzed. Comparison of the present results with those by others shows good agreement.

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Site characteristics and classification of seismic stations based on observed earthquake data (지진관측 자료를 이용한 국내 지진관측소의 지반특성 분류)

  • 박동희;연관희;장천중
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.03a
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    • pp.61-68
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    • 2003
  • The H/V ratio (Horizontal to Vertical spectral ratio) has been used to infer site amplification without previous knowledge of near-surface geology and in fact may provide useful general site condition information. This method is used to classify the site characteristics of seismic stations in Korea by comparison with known H/V ratios representative of various sites all over the world. In addition, differences between horizontal and vertical kappa values were evaluated for each seismic stations by comparing WV ratio and Weak Motion amplification derived from inversion of stochastic ground motion parameters and were used as index to quantitatively classify the site characteristics.

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Ground motion selection and scaling for seismic design of RC frames against collapse

  • Bayati, Zeinab;Soltani, Masoud
    • Earthquakes and Structures
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    • v.11 no.3
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    • pp.445-459
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    • 2016
  • Quantitative estimation of seismic response of various structural systems at the collapse limit state is one of the most significant objectives in Performance-Based Earthquake Engineering (PBEE). Assessing the effects of uncertainties, due to variability in ground motion characteristics and random nature of earthquakes, on nonlinear structural response is a pivotal issue regarding collapse safety prediction. Incremental Dynamic Analysis (IDA) and fragility curves are utilized to estimate demand parameters and seismic performance levels of structures. Since producing these curves based on a large number of nonlinear dynamic analyses would be time-consuming, selection of appropriate earthquake ground motion records resulting in reliable responses with sufficient accuracy seems to be quite essential. The aim of this research study is to propose a methodology to assess the seismic behavior of reinforced concrete frames at collapse limit state via accurate estimation of seismic fragility curves for different Engineering Demand Parameters (EDPs) by using a limited number of ground motion records. Research results demonstrate that accurate estimating of structural collapse capacity is feasible through applying the proposed method offering an appropriate suite of limited ground motion records.

Seismic Response Analysis of Bridges Considering Spatial Variation of Input Ground Motion (입력지반운동의 공간적 변화를 고려한 교량의 지진응답해석)

  • Choi, Kwang-Gyu;Kang, Seung-Woo;Kook, Seung-Kyu
    • Journal of Ocean Engineering and Technology
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    • v.24 no.1
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    • pp.76-82
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    • 2010
  • This paper presents a seismic response analysis of bridge structures considering the spatial variation of input ground motion. In earthquake analyses of structures, it is usually assumed that the input ground motion is the same at every support. However, this assumption is not justified for long structures like bridges, because observations have shown that the earthquake ground motion can vary considerably within relatively small distances. When the soil under the foundation is relatively soft and deep, an analysis of the foundation-soil interaction must always be performed. To consider the foundation-soil interaction, a soil response analysis is performed first, and after determining the material characteristics of the foundation element obtained by this foundation-soil interaction analysis, the seismic response analysis of a bridge superstructure with equivalent springs and dampers is performed. Finally, the influences of the spatial variation in the input motion, which are affected by different soil characteristics, are considered.

Three-Dimensional Simulation of Seismic Wave Propagation in Elastic Media Using Finite-Difference Method (유한차분법을 이용한 3차원 지진파 전파 모의)

  • 강태섭
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.10a
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    • pp.81-88
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    • 2000
  • The elastic wave equation is solved using the finite-difference method in 3D space to simulate the seismic wave propagation. It is based on the velocity-stress formulation of the equation of motion on a staggered grid. The nonreflecting boundary conditions are used to attenuate the wave field close to the numerical boundary. To satisfy the stress-free conditions at the free-surface boundary, a new formulation combining the zero-stress formalism with the vacuum one is applied. The effective media parameters are employed to satisfy the traction continuity condition across the media interface. With use of the moment-tensor components, the wide range of source mechanism parameters can be specified. The numerical experiments are carried out in order to test the applicability and accuracy of this scheme and to understand the fundamental features of the wave propagation under the generalized elastic media structure. Computational results show that the scheme is sufficiently accurate for modeling wave propagation in 3D elastic media and generates all the possible phases appropriately in under the given heterogeneous velocity structure. Also the characteristics of the ground motion in an sedimentary basin such as the amplification, trapping, and focusing of the elastic wave energy are well represented. These results demonstrate the use of this simulation method will be helpful for modeling the ground motion of seismological and engineering purpose like earthquake hazard assessment, seismic design, city planning, and etc..

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Assessment of 3D earthquake response of the Arhavi Highway Tunnel considering soil-structure interaction

  • Sevim, Baris
    • Computers and Concrete
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    • v.11 no.1
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    • pp.51-61
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    • 2013
  • This paper describes earthquake response of the Arhavi Highway Tunnel its geometrical properties, 3D finite element model and the linear time history analyses under a huge ground motion considering soil-structure interaction. The Arhavi Highway Tunnel is one of the tallest tunnels constructed in the Black Sea region of Turkey as part of the Coast Road Project. The tunnel has two tubes and each of them is about 1000 m tall. In the study, lineartime history analyses of the tunnel are performed applying north-south, east-west and up accelerations components of 1992 Erzincan, Turkey ground motion. In the time history analyses, Rayleigh damping coefficients are calculated using main natural frequency obtained from modal analysis. Element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motion. Because of needed too much memory for the analyses, the first 10 second of the ground motions, which is the most effective duration, is taken into account in calculations. The results obtained 3D finite element model are presented. In addition, the displacement and stress results are observed to be allowable level of the concrete material during the earthquakes.

Considerations for the Generation of In-Structure Response Spectra in Seismically Isolated Structures (면진구조물 내 층응답스펙트럼 작성을 위한 고려사항)

  • Lee, Seung Jae;Kim, Jung Han
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.2
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    • pp.95-103
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    • 2022
  • In order to evaluate the earthquake safety of equipment in structures, it is essential to analyze the In-Structure Response Spectrum (ISRS). The ISRS has a peak value at the frequency corresponding to the structural vibration mode, but the frequency and amplitude at the peak can vary because of many uncertain parameters. There are several seismic design criteria for ISRS peak-broadening for fixed base structures. However, there are no suggested criteria for constructing the design ISRS of seismically isolated structures. The ISRS of isolated structures may change due to the major uncertainty parameter of the isolator, which is the shear stiffness of the isolator and the several uncertainty parameters caused by the nonlinear behavior of isolators. This study evaluated the effects on the ISRS due to the initial stiffness of the bi-linear curve of isolators and the variation of effective stiffness by the input ground motion intensity and intense motion duration. Analyzing a simplified structural model for isolated base structure confirmed that the ISRS at the frequency of structural mode was amplified and shifted. It was found that the uncertainty of the initial stiffness of isolators significantly affects the shape of ISRS. The variation caused by the intensity and duration of input ground motions was also evaluated. These results suggested several considerations for generating ISRS for seismically isolated structures.

24 January 2020 Sivrice (Elazığ) earthquake damages and determination of earthquake parameters in the region

  • Isik, Ercan;Aydin, Mehmet Cihan;Buyuksarac, Aydin
    • Earthquakes and Structures
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    • v.19 no.2
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    • pp.145-156
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    • 2020
  • The 24 January 2020 (Mw=6.8) earthquake with epicentre in Elazığ (Sivrice) on the East Anatolian Fault Zone caused loss of life and property. The information was given about the seismotectonic setting and regional seismicity along this fault zone and aftershock activity and ground motion data of this earthquake. Earthquake parameters were obtained for five different earthquake stations which were closer to the epicentre. Horizontal and vertical design spectra were obtained for the geographic locations for each earthquake station. The obtained spectra for the earthquake epicentre were compared with selected appropriate attenuation relationships. The damages after earthquake were evaluated via geotechnical and structural aspects. This study also aims to investigate the cause-effect relationships between structural damage in reinforced-concrete and masonry structures, respectively. The lack of engineering services was effective on the amount of damage in masonry structures. Insufficient reinforcement and concrete strength, dimensions and inadequate detailing increased the amount of damage in reinforced-concrete structures. Importance should be given to negative parameters that may weaken the defence mechanisms of structures for earthquake-resistant structural design.

Earthquake Engineering Bedrock Based on the Shear Wave Velocities of Rock Strata in Korea (국내 암반지층의 전단파속도에 근거한 지진공학적 기반암 결정)

  • Sun, Chang-Guk
    • The Journal of Engineering Geology
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    • v.24 no.2
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    • pp.273-281
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    • 2014
  • In most current seismic design codes, design earthquake ground motions are defined by a reference spectrum, based on bedrock and site amplification factors that quantify the geotechnical dynamic conditions. Earthquake engineering bedrock is the fundamental geotechnical formation where the seismic waves are attenuated without amplification. To better define bedrock in an earthquake engineering context, shear wave velocity ($V_S$ ) data obtained from in-situ seismic tests were examined for several rock strata in Korea; these data were categorized by borehole drilling investigations. The $V_S$ values for most soft rock data in Korea are > 750 m/s, which is the threshold $V_S$ value for identifying engineering bedrock from a strong motion station. Conversely, VS values are < 750 m/s for 60% of $V_S$ data in weathered rock in Korea. Thus, the soft (or harder) rock strata below the weathered rock layer in Korea can be regarded as earthquake engineering bedrock.

Determination of critical excitation in seismic analysis of structures

  • Kamgar, Reza;Rahgozar, Reza
    • Earthquakes and Structures
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    • v.9 no.4
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    • pp.875-891
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    • 2015
  • Earthquake can occur anywhere in the world and it is essential to design important members in special structures based on maximum possible forces that can be produced in them under severe earthquake. In addition, since the earthquake is an accidental phenomena and there are no similar earthquakes, therefore the possibility of strong earthquakes should be taken into account in earthquake-resistant design of important structures. Based on this viewpoint, finding the critical acceleration which maximizes internal forces is an essential factor in structural design. This paper proposes critical excitation method to compute the critical acceleration in design of important members in special structures. These critical accelerations are computed so that the columns' internal shear force at the base of the structure at each time step is maximized under constraints on ground motion. Among computed critical accelerations (of each time step), the one which produces maximum internal shear force is selected. A numerical example presents to show the efficiency of critical excitation method in determining the maximum internal shear force and base moment under variety of constraints. The results show that these method can be used to compute the resonant earthquake which have large enough effective duration of earthquake strong motion (between 12.86 sec to 13.38 sec) and produce the internal shear force and base moment for specific column greater than the same value for selected earthquakes in constructing the critical excitation (for different cases about 2.78 to 1.29 times the San Fernando earthquake). Therefore, a group of them can be utilized in developing the response spectrum for design of special structures.