• 제목/요약/키워드: vertical seismic coefficient

검색결과 32건 처리시간 0.026초

고층 RC 벽식 비정형 구조물의 지진반응에 대한 비틀림 편심의 효과 (Effect of Torsional Eccentricity on the Seismic Response of High-Rise RC Bearing-Wall Structures with Vertical Irregularity)

  • 고동우;이한선
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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    • pp.145-150
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    • 2003
  • The objective of this study is to investigate the effect of torsional eccentricity on the seismic response of high-rise RC bearing-wall structures with vertical irregularity. For this purpose, two 1:12 scale 17-story RC model structures, the one has concentric shear wall and the other has eccentric shear wall, were constructed and then subjected to a series of earthquake excitations. The test result shows the followings: 1) the layout of shear wall has the negligible effect on the natural period and the base shear coefficient, 2) the eccentric model behaves in the first and second mode while the concentric model has the first mode predominantly, 3) the stiff frame in the eccentric model resists most of overturning moment in the severe earthquake though both frames (the stiff and flexible frames) resist almost equally in the design earthquake.

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Probabilistic seismic hazard assessment of Sanandaj, Iran

  • Ghodrati Amiri, Gholamreza;Andisheh, Kaveh;Razavian Amrei, Seyed Ali
    • Structural Engineering and Mechanics
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    • 제32권4호
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    • pp.563-581
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    • 2009
  • In this paper, the peak horizontal ground acceleration over the bedrock (PGA) is calculated by a probabilistic seismic hazard assessment (PSHA). For this reason, at first, all the occurred earthquakes in a radius of 200 km of Sanandaj city have been gathered. After elimination of the aftershocks and foreshocks, the main earthquakes were taken into consideration to calculate the seismic parameters (SP) by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. In this research, Sanandaj and its vicinity has been meshed as an 8 (vertical lines) * 10 (horizontal lines) and the PGA is calculated for each point of the mesh using the logic tree method and the five attenuation relationships (AR) with different weighted coefficient. These calculations have been performed by the Poisson distribution of four hazard levels. Then by using it, four regional maps of the seismic hazard regions have been provided for Sanandaj and its vicinity. The results show that the maximum and minimum value of PGA for the return periods of 75, 225, 475, 2475 years are (0.114, 0.074) (0.157, 0.101), (0.189, 0.121) and (0.266, 0.170), respectively.

Lateral earth pressure and bending moment on sheet pile walls due to uniform surcharge

  • Singh, Akshay Pratap;Chatterjee, Kaustav
    • Geomechanics and Engineering
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    • 제23권1호
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    • pp.71-83
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    • 2020
  • Cantilever sheet pile walls are subjected to surcharge loading located on the backfill soil and at different distances from the top of the wall. The response of cantilever sheet pile walls to surcharge loadings at varying distances under seismic conditions is scarce in literature. In the present study, the influence of uniform surcharge load on cantilever sheet pile wall at varying distances from the top of the wall under seismic conditions are analyzed using finite difference based computer program. The results of the numerical analysis are presented in non-dimensional form like variation of bending moment and horizontal earth pressure along the depth of the sheet pile walls. The numerical analysis has been conducted at different magnitudes of horizontal seismic acceleration coefficient and vertical seismic acceleration coefficients by varying the magnitude and position of uniform surcharge from the top of the wall for different embedded depths and types of soil. The parametric study is conducted with different embedded depth of sheet pile walls, magnitude of surcharge on the top of the wall and at a distance from the top of the wall for different angles of internal friction. It is observed that the maximum bending moment increases and more mobilization of earth pressure takes place with increase in horizontal seismic acceleration coefficients, magnitude of uniform surcharge, embedded depth and decrease in the distance of surcharge from the top of the wall in loose sand.

1차원 지반응답해석을 통한 사면의 증폭특성 규명 (Estimation of amplification of slope via 1-D site response analysis)

  • 윤세웅;박두희
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2009년도 춘계 학술발표회
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    • pp.620-625
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    • 2009
  • The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops the modified one-dimensional seismic site response analysis. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses are performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure are compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match.

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Seismic evaluation of RC stepped building frames using improved pushover analysis

  • Sarkar, Pradip;Prasad, A. Meher;Menon, Devdas
    • Earthquakes and Structures
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    • 제10권4호
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    • pp.913-938
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    • 2016
  • 'Stepped building' frames, with vertical geometric irregularity, are now increasingly encountered in modern urban constructions. This paper proposes a new approach to determine the lateral load pattern, considering the contributions from the higher modes, suitable for pushover analysis of stepped buildings. Also, a modification to the displacement coefficient method of ASCE/SEI 41-13 is proposed, based on nonlinear time history analysis of 78 stepped frames. When the newly proposed load pattern is combined with the modified displacement coefficient method, the target displacement for the stepped building frame is found to match consistently the displacement demand given by the time history analysis.

지진을 받는 현수교의 수직진동 (Vertical Seismic Vibration of Suspension Bridges)

  • 최지훈;이존자;김수보;이용재
    • 한국강구조학회 논문집
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    • 제12권5호통권48호
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    • pp.581-593
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    • 2000
  • 본 연구는 지진하중을 받는 현수교의 수직 동적 해석방법을 발전시켰다. 시간 영역해석, 불규칙 진동 해석 및 스펙트럼 해석의 이론을 체계적으로 정립하였다. 불규칙 진동 해석을 다시 수치적분을 이용하는 방법과 수학적 적분식 및 상관계수를 이용한 방법으로 나누고 각각은 다시 지진하중을 white noise로 가정한 경우와 filtered white noise로 가정한 경우에 대해 CQC 방법과 SRSS 방법을 사용하였다. 현수교의 모델링은 빔, 트러스 및 프레임요소를 사용하였고 케이블과 주탑은 사하중에 의한 기하학적 강성을 고려하였다.

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암석시편의 균열조사를 위한 탄성파 주시 및 진폭 변화에 관한 연구 (Study of seismic traveltime and amplitude effect to detect to detect cracks in rock)

  • 서백수;백환조;민경원
    • 터널과지하공간
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    • 제6권3호
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    • pp.239-244
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    • 1996
  • Cracks have influence on the physical and mechanical and, more importantly, on the engineering properties of the rock. Physical properties including the volumetric deformation coefficient, electrical resistivity, seismic wave velocity, and the mechanical properties such as the elastic constants and strength of rock are affected significantly by the presence of cracks of various sizes. An experimental program was undertaken to investigate the effect of a finite line crack on the diffraction of the plane compressional wave. Horizontal and vertical components of displacement and acceleration curve were obtained using a single-source and multi-receivers system. A theoretical model from numerical analysis implementing the finite element method was compared with the measured data.

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지진하중을 받는 철근콘크리트 장주의 P-$\Delta$ 효과 (Seismic P-$\Delta$ Effects of Slender RC Columns in Earthquake Analysis)

  • 곽효경;김진국
    • 한국전산구조공학회논문집
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    • 제19권4호
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    • pp.375-387
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    • 2006
  • 기존의 연구에서 가정된 모멘트-곡률 관계를 토대로 고정된 안정계수를 갖는 응답스펙트럼을 구성하여 동적 P-$\Delta$ 효과를 분석한 것과는 달리, 이 논문에서는 안정계수의 증가, 즉, 축력의 증가에 따른 하중-변위관계의 변화를 고려할 수 있도록하는 적층단면법을 토대로 실용범위의 세장비와 안정계수를 변화시켜가며, 해석을 수행하여 철근콘크리트 장주의 동적 P-$\Delta$ 효과를 분석하였다. 다양한 지진에 대한 보편화된 결과를 얻기 위해 각기 다른 60개의 입력지진을 사용하였다. 또한, 수평지진과 수직지진을 동시에 작용하여 해석을 수행해 수직지진에 따른 P-$\Delta$ 효과를 살펴보았다. 해석결과, 철근콘크리트 장주의 최대변형은 축력, P-$\Delta$ 효과 및 수직지진의 영향을 거의 받지 않는 반면, 부재 내력은 축력에 의한 강성과 항복강도의 증가에 의해 증가하기 때문에, 철근콘크리트 장주의 내진설계시 축력효과를 고려하여 설계할 경우 P-$\Delta$ 효과 또는 수직지진에 대한 추가적인 영향은 고려하지 않아도 될 것으로 판단된다.

고속열차 주행 시 지진하중을 고려한 현수교의 주행안전성 및 승차감 분석 (Traffic Safety & Passenger Comforts of a Suspension Bridge Considering Seismic Loads)

  • 김성일;김동석
    • 한국철도학회논문집
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    • 제14권1호
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    • pp.57-65
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    • 2011
  • 교량을 주행하는 열차의 주행안전성과 승차감의 확보를 위해 Eurocode, 신간선 기준, 호남고속철도 설계지침 등에서는 교량의 연직변위, 연직가속도, 면틀림 등의 항목으로 제한하고 있다. 그러나 이와 같은 제한 기준은 교량 설계자의 편의를 위한 간접적인 방법이다. 또한 이와 같은 기준은 일반적인 경간(Eurocode의 경우 120m 이하)에 대한 제한 기준으로서, 이 이상의 장경간 교량의 경우에는 교량/열차 상호작용 해석 등에 의한 면밀한 검토를 제안하고 있다. 본 연구에서는 교량/열차 상호작용 해석을 수행하여 열차에서의 응답을 통해 교량 상을 주행하는 열차의 주행안전성 및 승차감을 직접적으로 평가하고자 하였다. 즉, 중앙경간 300m의 현수교를 주행하는 KTX 열차에 대하여 열차 내부의 가속도와 윤중감소율을 구해 평가하는 방법을 취하였다. 또한, 이동 열차하중과 지진하중이 동시에 작용할 경우를 고려한 교량/열차/지진 상호작용해석을 수행하여 지진 시의 응답을 평가하였다.

Seismic progressive collapse mitigation of buildings using cylindrical friction damper

  • Mirtaheri, Masoud;Omidi, Zobeydeh;Salkhordeh, Mojtaba;Mirzaeefard, Hamid
    • Earthquakes and Structures
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    • 제20권1호
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    • pp.1-12
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    • 2021
  • The occurrence of progressive collapse induced by the removal of the vertical load-bearing element in the structure, because of fire or earthquake, has been a significant challenge between structural engineers. Progressive collapse is defined as the complete failure or failure of a part of the structure, initiating with a local rupture in a part of the building and can threaten the stability of the structure. In the current study, the behavior of the structures equipped with a cylindrical friction damper, when the vertical load-bearing elements are eliminated, is considered in two cases: 1-The load-bearing element is removed under the gravity load, and 2-The load-bearing element is removed due to the earthquake lateral forces. In order to obtain a generalized result in the seismic case, 22 pair motions presented in FEMA p 695 are applied to the structures. The study has been conducted using the vertical push down analysis for the case (1), and the nonlinear time-history analysis for the second case using OpenSEES software for 5,10, and 15-story steel frames. Results indicate that, in the first case, the load coefficient, and accordingly the strength of the structure equipped with cylindrical friction dampers are increased considerably. Furthermore, the results from the second case demonstrate that the displacements, and consequently the forces imposed to the structure in the buildings equipped with the cylindrical friction damper substantially was reduced. An optimum slip load is defined in the friction dampers, which permits the damper to start its frictional damping from this threshold load. Therefore, the optimum slip load of the damper is calculated and discussed for both cases.