• Title/Summary/Keyword: Seismic Loads

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Analysis of Behavior for Underground Flexible Pipes Under Seismic Loads (지진발생에 따른 지중연성관의 거동특성 분석)

  • 김경열;홍성연;이대수
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.709-716
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    • 2003
  • Flexible pipes (corrugated polyethylene pipes) are normally used for underground power distribution grids. In this paper, dynamic analysis was carried out through FEM in order to investigate the structural behaviour of pipes subjected to seismic loads. The burial depth and the number of pipes were major parameters in the numerical analysis to determine the response of pipes. The results show that the displacement of pipes under given conditions are all satisfactory in comparison of the allowable strain criteria -maximum 3.5 %.

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Simplified elastic-plastic analysis procedure for strain-based fatigue assessment of nuclear safety class 1 components under severe seismic loads

  • Kim, Jong-Sung;Kim, Jun-Young
    • Nuclear Engineering and Technology
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    • v.52 no.12
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    • pp.2918-2927
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    • 2020
  • This paper proposes a simplified elastic-plastic analysis procedure using the penalty factors presented in the Code Case N-779 for strain-based fatigue assessment of nuclear safety class 1 components under severe seismic loads such as safety shutdown earthquake and beyond design-basis earthquake. First, a simplified elastic-plastic analysis procedure for strain-based fatigue assessment of nuclear safety class 1 components under the severe seismic loads was proposed based on the analysis result for the simplified elastic-plastic analysis procedure in the Code Case N-779 and the stress categories corresponding to normal operation and seismic loads. Second, total strain amplitude was calculated directly by performing finite element cyclic elastic-plastic seismic analysis for a hot leg nozzle in pressurizer surge line subject to combined loading including deadweight, pressure, seismic inertia load, and seismic anchor motion, as well as was derived indirectly by applying the proposed analysis procedure to the finite element elastic stress analysis result for each load. Third, strain-based fatigue assessment was implemented by applying the strain-based fatigue acceptance criteria in the ASME B&PV Code, Sec. III, Subsec. NB, Article NB-3200 and by using the total strain amplitude values calculated. Last, the total strain amplitude and the fatigue assessment result corresponding to the simplified elastic-plastic analysis were compared with those using the finite element elastic-plastic seismic analysis results. As a result of the comparison, it was identified that the proposed analysis procedure can derive reasonable and conservative results.

A study of the rail and bridge stability according to rail conditions on the bridge (교량상 레일 조건에 따른 레일 및 교량의 안전성 연구)

  • Min, Kyung-Ju;Kim, Young-Kook;Woo, Yong-Keun
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.505-515
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    • 2009
  • In railway bridges, various loads including train load, transverse load and braking force are applied to continuous CWR or semi-continuous longer rail located on non-continuous bridge superstructures. The rail-girder interaction due to thermal expansion is also very complex in railway bridges because the thermal characteristics for each of the rails and girder are quite different. Recently, the bridge retrofits for seismic loads were performed on bridges not designed for these loads. These retrofits may however have limitations with respect to rail-girder interactions because, in general these retrofits address issues related only to seismic loads. In this study of seismic evaluations for railway bridges, the load effects on the bridge rails from the road beds through the continuous rails shall be considered. Practical methods will be proposed which will increase the railway stability. For this, rail-girder interaction analyses due to train loads, temperature changes and seismic loads were performed and the results reviewed from a practical point of view.

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Some practical considerations in designing underground station structures for seismic loads

  • Gu, Jianzhong
    • Structural Engineering and Mechanics
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    • v.54 no.3
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    • pp.491-500
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    • 2015
  • Under seismic loading, underground station structures behave differently from above ground structures. Underground structures do not require designated energy dissipation system for seismic loads. These structures are traditionally designed with shear or racking deformation capacity to accommodate the movement of the soil caused by shear waves. The free-field shear deformation method may not be suitable for the design of shallowly buried station structures with complex structural configurations. Alternatively, a station structure can develop rocking mechanisms either as a whole rigid body or as a portion of the structure with plastic hinges. With a rocking mechanism, station structures can be tilted to accommodate lateral shear deformation from the soil. If required, plastic hinges can be implemented to develop rocking mechanism. Generally, rocking structures do not expect significant seismic loads from surrounding soils, although the mechanism may result in significant internal forces and localized soil bearing pressures. This method may produce a reliable and robust design of station structures.

Behaviour of Multi-Storey Prefabricated Modular Buildings under seismic loads

  • Gunawardena, Tharaka;Ngo, Tuan;Mendis, Priyan
    • Earthquakes and Structures
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    • v.11 no.6
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    • pp.1061-1076
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    • 2016
  • Prefabricated Modular Buildings are increasingly becoming popular in the construction industry as a method to achieve financially economical buildings in a very short construction time. This increasing demand for modular construction has expanded into multi-storey applications where the effect of lateral loads such as seismic loads becomes critical. However, there is a lack of detailed scientific research that has explored the behaviour of modular buildings and their connection systems against seismic loads. This paper will therefore present the nonlinear time history analysis of a multi-storey modular building against several ground motion records. The critical elements that need special attention in designing a modular building in similar seismic conditions is discussed with a deeper explanation of the behaviour of the overall system.

Structural Analysis of a Breakwater in Wave and Seismic Loads (파랑하중과 지진하중하의 방파제 구조해석)

  • Cho, Kyu-Nam
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.1
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    • pp.45-52
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    • 2009
  • In this paper, a guideline for designing breakwater in wave loads and in seismic loads is proposed. A simple model structure in breaking wave zone is examined using Morison equation in consideration with the effect of an impact load, for evaluation of the wave loads. As the impact load effect is not significant, pressure distributions according to Goda are applied for evaluation of wave loads on breakwater. Structural behavior of breakwater in wave loads can be obtained using the Goda method, as well. For seismic analysis, Ofunato and Hachinohe models, as well as an artificial seismic acceleration loads model, are adopted. Soil-structure interaction analysis is carried out to find the seismic load effect. It is found that, in certain cases, structural deformation in wave loads is in the same level as deformation that in seismic loads. Thus, it is our recommendation that these two loads are considered at the same level in breakwater design.

Examination of Seismic Design for High-Rise Steel Frames Under Huge Earthquake Using Element Bi-linear Time-History Analysis (부재별 탄소성 이력해석을 이용한 거대 지진에서의 고층 강구조 건물 내진 설계 검정)

  • Kim, Moon-Jeong
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.2 no.4
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    • pp.28-34
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    • 2011
  • Because strong urban earthquakes must produce huge losses of both life and property, examinations about the effect of huge earthquakes for tall buildings are very required. The goal of this report is examining model safety and compare the behavior of 2-D tall models under huge seismic loads. This report examines high-rise models designed KBC2009 codes using 1) seismic loads regulated by KBC2009 and 2) amplified seismic loads assumed to strong earthquakes. And observing for more realistic behavior of tall buildings under huge earthquakes, this report takes two analysis methods - response spectrum analysis and non-linear time history analysis considering P-delta effect.

Design of integral abutment bridges for combined thermal and seismic loads

  • Far, Narges Easazadeh;Maleki, Shervin;Barghian, Majid
    • Earthquakes and Structures
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    • v.9 no.2
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    • pp.415-430
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    • 2015
  • Integral abutment bridges have many advantages over bridges with expansion joints in terms of economy and maintenance costs. However, in the design of abutments of integral bridges temperature loads play a crucial role. In addition, seismic loads are readily transferred to the substructure and affect the design of these components significantly. Currently, the European and American bridge design codes consider these two load cases separately in their recommended design load combinations. In this paper, the importance and necessity of combining the thermal and seismic loads is investigated for integral bridges. A 2D finite element combined pile-soil-structure interactive model is used in this evaluation. Nonlinear behavior is assumed for near field soil behind the abutments. The soil around the piles is modeled by nonlinear springs based on p-y curves. The uniform temperature changes occurring at the time of some significant earthquakes around the world are gathered and applied simultaneously with the corresponding earthquake time history ground motions. By comparing the results of these analyses to prescribed AASHTO LRFD load combinations it is observed that pile forces and abutment stresses are affected by this new load combination. This effect is more severe for contraction mode which is caused by negative uniform temperature changes.

Seismic lateral earth pressure analysis of retaining walls

  • Ismeik, Muhannad;Shaqour, Fathi
    • Geomechanics and Engineering
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    • v.8 no.4
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    • pp.523-540
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    • 2015
  • Based on limit equilibrium principles, this study presents a theoretical derivation of a new analytical formulation for estimating magnitude and lateral earth pressure distribution on a retaining wall subjected to seismic loads. The proposed solution accounts for failure wedge inclination, unit weight and friction angle of backfill soil, wall roughness, and horizontal and vertical seismic ground accelerations. The current analysis predicts a nonlinear lateral earth pressure variation along the wall with and without seismic loads. A parametric study is conducted to examine the influence of various parameters on lateral earth pressure distribution. Findings reveal that lateral earth pressure increases with the increase of horizontal ground acceleration while it decreases with the increase of vertical ground acceleration. Compared to classical theory, the position of resultant lateral earth force is located at a higher distance from wall base which in turn has a direct impact on wall stability and economy. A numerical example is presented to illustrate the computations of lateral earth pressure distribution based on the suggested analytical method.