• 한국항공우주학회지
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• 제30권4호
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• pp.10-17
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• 2002

간접 경계요소법 (비정상패널법)을 사용하여 3차원 날개의 동적 지면효과에 대한 연구를 수행하였다. Green 정리를 사용하여 경계표면에 대한 적분방정식을 얻었다. 일정강도의 용출 및 용흡중첩을 날개표면에 분포시켰고 후류는 일정강도의 용흡중첩으로 나타내었다. 매 시간간격마다 한 행의 후류 패널들이 날개의 후연에서 하류로 대류한다고 가정하였다. 지면효과를 받는 날개의 익단 와류가 날개길이방향으로 이동하였다. 동적 지면효과를 받는 날개가 가지는 공력계수의 진폭 값이 정적 지면효과를 받는 날개의 경우보다 더욱 증가하였다.

• Earthquakes and Structures
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• 제17권6호
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• pp.557-566
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• 2019

The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and site local conditions. The aim of this work is to evaluate the sensitivity of dynamic response of extended structures to spatial variable ground motions (SVGM). All factors of spatial variability of ground motion are considered, especially local site effect. In this paper, a method is presented to simulate spatially varying earthquake ground motions. The scheme for generating spatially varying ground motions is established for spatial locations on the ground surface with varying site conditions. In this proposed method, two steps are necessary. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi-Kanai power spectral density function. An empirical coherency loss model is used to define spatial variable seismic ground motions at the base rock. In the second step, power spectral density function of ground motion on surface is derived by considering site amplification effect based on the one dimensional seismic wave propagation theory. Several dynamics analysis of a curved viaduct to various cases of spatially varying seismic ground motions are performed. For comparison, responses to uniform ground motion, to spatial ground motions without considering local site effect, to spatial ground motions with considering coherency loss, phase delay and local site effects are also calculated. The results showed that the generated seismic signals are strongly conditioned by the local site effect. In the same sense, the dynamic response of the viaduct is very sensitive of the variation of local geological conditions of the site. The effect of neglecting local site effect in dynamic analysis gives rise to a significant underestimation of the seismic demand of the structure.

• 한국재난정보학회 논문집
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• 제6권2호
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• pp.45-65
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• 2010

There has been tighten up the need of seismic retrofit about 31 public facilites since published "Korean Earthquake Damage Prevention Law". Therefore, seismic studies have been developed and enforced the studies. Measuring dynamic stiffness of subsurface materials influence on seismic performance evaluation to build up seismic retrofit. The soil dynamic properties for seismic performance evaluation are N-value from using SPT(standard penetration test), dynamic shear elastic modulus and dynamic deformation modulus using laboratory tests. The most unscientific element in ground dynamic properties involved uncertainties is obviously N-value using SPT. This study shows that effect of N-value included natural and artificial uncertainties to seismic performance evaluation of ground structures is not only approached probabilistic analysis using FOSM method and tornado diagram, but also review how to spread effect of seismic performance evaluation of ground structures.

• Earthquakes and Structures
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• 제14권5호
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• pp.399-409
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• 2018

The dynamic response and seismic damage of single-layer reticulated shells in the near field of a rupturing fault can be different from those in the far field due to the different characteristics in the ground motions. To investigate the effect, the dynamic response and seismic damage of this spatial structures subjected to two different ground motions were numerically studied by nonlinear dynamic response analysis. Firstly, twelve seismic waves with an apparent velocity pulse, including horizontal and vertical seismic waves, were selected to represent the near-fault ground motion characteristics. In contrast, twelve seismic records recorded at the same site from other or same events where the epicenter was far away from the site were employed as the far-fault ground motions. Secondly, the parametric modeling process of Kiewitt single-layer reticulated domes using the finite-element package ANSYS was described carefully. Thirdly, a nonlinear time-history response analysis was carried out for typical domes subjected to different earthquakes, followed by analyzing the dynamic response and seismic damage of this spatial structures under two different ground motions based on the maximum nodal displacements and Park-Ang index as well as dissipated energy. The results showed that this spatial structures in the near field of a rupturing fault exhibit a larger dynamic response and seismic damage than those obtained from far-fault ground motions. In addition, the results also showed that the frequency overlap between structures and ground motions has a significant influence on the dynamic response of the single-layer reticulated shells, the duration of the ground motions has little effects.

• 한국공간구조학회논문집
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• 제18권3호
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• pp.105-116
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• 2018

The objective of this study is to investigate the response reducing effect of a seismic isolation system installed between 300m dome and supports under both horizontal and vertical seismic ground motion. The time history analysis is performed to investigate the dynamic behavior of single layer lattice domes with and without a lead rubber bearing seismic isolation system. In order to ensure the seismic performance of lattice domes against strong earthquakes, it is important to investigate the mechanical characteristics of dynamic response. Horizontal and vertical seismic ground motions cause a large asymmetric vertical response of large span domes. One of the most effective methods to reduce the dynamic response is to install a seismic isolation system for observing seismic ground motion at the base of the dome. This paper discusses the dynamic response characteristics of 300m single layer lattice domes supported on a lead rubber seismic isolation device under horizontal and vertical seismic ground motions.

• 한국지반환경공학회 논문집
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• 제22권7호
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• pp.5-12
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• 2021

The reliable seismic stability evaluation of the natural slopes and geotechnical structures has become a critical factor of the design. Pseudo-static or permanent displacement methods are typically employed to evaluate the seismic slope performance. In both methods, the effect of input ground motion on the sliding surface is ignored, and failure surface from the limit equilibrium method is used. For the assessment of the seismic sensitivity of failure surface, two-dimensional non-linear finite element analyses are performed. The performance of the finite element model was validated against centrifuge measurements. A parametric study with a range of input ground motion was performed, and numerical results were used to assess the influence of ground motion characteristics on the sliding surface. Based on the results, it is demonstrated that the characteristics of input ground motion have a significant influence on the location of the seismically induce failure surface. In addition to dynamic analysis, pseudo-static analyses were performed to evaluate the discrepancy. It is observed that sliding surfaces developed from pseudo-static and dynamic analyses are different. The location of the failure surface change with the amplitude and T_m of motion. Therefore, it is recommended to determine failure surfaces from dynamic analysis

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.642-647
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• 2001

Dynamic response of ground due to train loads is analyzed. A numerical procedure based on finite element method is used to solve two-dimensional ground response. Dynamic train loads assumed in analysis is the point acceleration on train rail with magnitude of 2330 gal and thickness of surface of soil layer assumed is 60cm. In order to consider the effect of acceleration point, dynamic responses such as response acceleration and displacement are computed as a function of distance from acceleration point on rail. In addition, simple methods which reduce dynamic effects on ground are also proposed.

• Earthquakes and Structures
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• 제12권3호
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• pp.297-307
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• 2017

Evaluation on the sidesway seismic collapse capacity of the widely used low- and medium-height structures is meaningful. These structures with such type of collapse are recognized that behave as inelastic deteriorating single-degree-of-freedom (SDOF) systems. To incorporate the deteriorating effects, the hysteretic loop of the nonlinear SDOF structural model is represented by a tri-linear force-displacement relationship. The concept of collapse capacity spectra are adopted, where the incremental dynamic analysis is performed to check the collapse point and a normalized ground motion intensity measure corresponding to the collapse point is used to define the collapse capacity. With a large amount of earthquake ground motions, a systematic parameter study, i.e., the influences of various ground motion parameters (site condition, magnitude, distance to rupture, and near-fault effect) as well as various structural parameters (damping, ductility, degrading stiffness, pinching behavior, accumulated damage, unloading stiffness, and P-delta effect) on the structural collapse capacity has been performed. The analytical formulas for the collapse capacity spectra considering above influences have been presented so as to quickly predict the structural collapse capacities.

• Earthquakes and Structures
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• 제10권5호
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• pp.1233-1251
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• 2016

In this paper, it is aimed to determine the stochastic response of a suspension bridge subjected to spatially varying ground motions considering the geometric nonlinearity. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of the ground motion is considered with the incoherence, wave-passage and site-response effects. The importance of site-response effect which arises from the difference in the local soil conditions at different support points of the structure is also investigated. At the end of the study, mean of the maximum and variance response values obtained from the spatially varying ground motions are compared with those of the specialised cases of the ground motion model. It is seen that each component of the spatially varying ground motion model has important effects on the dynamic behaviour of the bridge. The response values obtained from the general excitation case, which also includes the site-response effect causes larger response values than those of the homogeneous soil condition cases. The variance values calculated for the general excitation case are dominated by dynamic component at the deck and Asian side tower. The response values obtained for the site-response effect alone are larger than the response values obtained for the incoherence and wave-passage effects, separately. It can be concluded that suspension bridges are sensitive to the spatial variability of ground motion. Therefore, the incoherence, the wave-passage and especially the site-response effects should be considered in the stochastic analysis of this type of engineering structures.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1159-1164
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• 2005

Seismic analysis methods in use on ground structure are equivalentstatic analysis, response-displacement method and dynamic analysis etc. Equivalentstatic analysis does not considerdynamic effect, and dynamic analysis process is very complex. then 'Urbanrail transit earthquake-resistance design standard (2005.06)' is persuading that analyze by response displacement method that consider enough dynamic effect of ground structure statically. But, It is very complex and difficult to apply response-displacement method in the field. So, modified equivalentstatic analysis or pseudo static analysis that is easy to apply in the field and have rationality of design is practically used. In this study, I try to prescribe the applicable scale of structure and static analysis that have calculative effectiveness about response-displacement method by comparing and analyzing the result of each analysis method according to the scale of urban rail transit' box type concrete structure and by performing seismic analysis that apply modified equivalentstatic analysis, pseudo static analysis and response-displacement method changing the kind of ground, depth of bedrock, size of structure.