• 한국공간구조학회논문집
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• 제20권4호
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• pp.169-176
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• 2020

When an unexpected excessive seismic load is applied to the base isolation of arch structure, the seismic displacement of the base isolation may be very large beyond the limit displacement of base isolation. These excessive displacement of the base isolation causes a large displacement in the upper structure and large displacement of upper structure causes structural damage. Therefore, in order to limit the seismic displacement response of the base isolation, it is necessary to install an additional device such as an anti-uplift device to the base isolation. In this study, the installation direction of the base isolation and the control performance of the base isolation installed anti-uplift device were investigated. The installation direction of the base isolation of the arch structure is determined by considering the horizontal and vertical reaction forces of the arch structure. In addition, the separation distance of the anti-uplift device is determined in consideration of the design displacement of the base isolation and the displacement of the arch structure.

• Geomechanics and Engineering
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• 제11권1호
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• pp.141-160
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• 2016

This study elucidates the uplift behaviors of the straight-sided and belled shafts. The field uplift load tests were carried out on 18 straight-sided and 15 belled shafts at the three collapsible loess sites under an arid environment on the Loess Plateau in Northwest China. Both the site conditions and the load tests were documented comprehensively. In general, the uplift load-displacement curves of the straight-sided and belled shafts approximately exhibited an initial linear, a curvilinear transition, and a final linear region, but did not provide a well defined peak or asymptotic value of the load, and therefore their uplift resistances should be interpreted from the load test results using an appropriate criterion. Nine representative uplift resistance interpretation criteria were used to define the "interpreted failure load" for each of the load tests, and all of these interpreted uplift resistances were normalized by the failure threshold, $T_{L2}$, obtained using the $L_1-L_2$ method. These load test data were compared statistically and graphically. For the straight-sided and belled shafts, the normalized uplift load-displacement curves were respectively established by the plots that related the mean interpreted uplift resistance ratio against the mean displacement at the corresponding interpreted criteria, and the comparisons of the normalized load-displacement curves were made. Specific recommendations for the designs of uplift belled and straight-sided shafts in the loess were given, in terms of both capacity and displacement.

• Geomechanics and Engineering
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• 제11권2호
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• pp.211-234
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• 2016

A total of 99 full-scale field load tests at 22 sites were compiled for this study to elucidate several issues related to the load-displacement behaviour of belled piers under axial uplift loading, including (1) interpretation criteria to define various elastic, inelastic, and "failure" states for each load test from the load-displacement curve; (2) generalized correlations among these states and determinations to the predicted ultimate uplift resistances; (3) uncertainty in the resistance model factor statistics required for reliability-based ultimate limit state (ULS) design; (4) uncertainty associated with the normalized load-displacement curves and the resulting model factor statistics required for reliability-based serviceability limit state (SLS) design; and (5) variations of the combined ULS and SLS model factor statistics for reliability-based limit state designs. The approaches discussed in this study are practical and grounded realistically on the load tests of belled piers with minimal assumptions. The results on the characterization and uncertainty of uplift load-displacement behaviour of belled piers could be served as to extend the early contributions for reliability-based ULS and SLS designs.

• 한국지반공학회논문집
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• 제28권10호
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• pp.5-16
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• 2012

지진에 의해 지반의 액상화가 발생하면 상대적으로 가벼운 지중 매설구조물은 부상하는 현상이 발생하며 이러한 피해는 과거 여러 지진에서 계속해서 보고되고 있다. Koseki et al.(1997a)에 의해 제안된 안전율은 액상화 지반에서 매설구조물의 부상 유무를 판단할 수 있으며 현재 내진설계에 이용되고 있지만 부상량의 "정량적인" 예측은 불가능하며 아직 확립되지 않았다. 지중 매설구조물의 부상량의 예측은 구조물의 성능성과 관련 있는 내진성능설계에 있어서 중요한 요소가 된다(ISO23469, 2005). 따라서 지중 매설구조물에 대한 내진성능평가를 위해 실용적인 부상량의 평가가 필요하다. 지중 매설구조물의 부상량을 예측하기 위한 방법으로 구조물에 작용하는 수직방향 힘의 평형을 바탕으로 간이법이 정식화 되었고(Tobita et al., 2012), 간이법의 신뢰성 확보를 위해 원심모형시험 결과 및 2004년 니가타켄츄에츠 지진시의 매설구조물 피해와 비교하였다. 본 연구에서 제안된 내진성능설계 흐름도는 뒷채움의 액상화 판정뿐만 아니라, 지중 매설구조물의 부상량 예측도 가능하다.

• Earthquakes and Structures
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• 제15권5호
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• pp.555-564
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• 2018

Allowing structures to uplift in earthquakes can significantly reduce or even avoid the development of plastic hinges within the structure. The permanent deformations in the structure can thus be minimized. However, uplift of footings can cause additional horizontal movements of a structure. With an increase in movement relative to adjacent structures, the probability of pounding between structures increases. This experimental study reveals that the footing mass can be used to control the vertical displacement of footing and thus reduce the horizontal displacements of an upliftable structure. A four storey model structure with plastic hinges and uplift capability was considered. Shake table tests using ten different earthquake records were conducted. Three different footing masses were considered. It is found that the amplitude of footing uplift can be greatly reduced by increasing the mass of the footing. As a result, allowing structural uplift does not necessary increase the horizontal displacement of the structure. The results show that with increasing footing weight, the interaction between structural and footing response can increase the contribution of the higher modes to the structural response. Consequently, the induced vibrations on secondary structure increase.

• 생물환경조절학회지
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• 제10권3호
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• pp.148-154
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• 2001

본 연구에서는 1-2W형 플라스틱피복 파이프 온실의 내풍성을 증대시키기 위하여 형상 및 직경이 서로 다른 말뚝에 대하여 인발저항력을 검토하였다. 그 결과 민말뚝의 경우, 인발하중이 증가함에 따라 인발저항력은 증가하지만, 대부분의 경우 인발변위가 발생한 직후의 하중단계에서 극한인발저항력에 도달하였다. 그러나 주름말뚝의 경우는 인발변위가 발생한 이후에도 실험을 종료할 때까지 인발저항력의 증감이 반복되는 경향을 나타내었다. 그리고 기초의 형상, 직경 및 매입깊이에 따라 극한인발저항력은 다르지만, 본 실험의 경우 직경과 매입깊이에 관계없이 극한인발저항력은 주름말뚝이 민말뚝보다 약 2배 정도 크게 나타났다. 단위면적당 극한인발저항력은 매입깊이가 깊어질수록 증가하지만, 직경이 커지면 감소하였다. 실험 대상지역의 설계풍속(26.9m.s$^{-1}$)을 고려하면, 민말뚝은 매입깊이에 관계없이 기초의 인발저항력이 부족하였고, 주름말뚝의 경우은 대부분의 실험조건에서 충분한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제77권3호
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• pp.369-381
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• 2021

The seismic responses of elevated tanks considering liquid-structure interaction are presented under horizontal earthquake. The scaled model tank is fabricated to study the dynamic responses of anchored tank and newly designed uplift tank with replaced dampers. The natural frequencies for structural mode are obtained by modal analysis. The dynamic responses of tanks are completed by finite element method, which are compared with the results from experiment. The displacement parallel and perpendicular to the excitation direction are both gained as well as structural acceleration. The strain of tank walls and the axial strain of columns are also obtained afterwards. The seismic responses of liquid storage tank can be calculated by the finite element model effectively and the results match well with the one measured by experiment. The aim is to provide a new type of tank system with vertical constraint relaxed which leads to lower stress level. With the liquid volume increasing, the structural fundamental frequency has a great reduction and the one of uplift tank are even smaller. Compared with anchored tank, the displacement of uplift tank is magnified, the strain for tank walls and columns parallel to excitation direction reduces obviously, while the one perpendicular to earthquake direction increases a lot, but the values are still small. The stress level of new tank seems to be more even due to uplift effect. The new type of tank can realize recoverable function by replacing dampers after earthquake.

• 한국농공학회지
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• 제40권4호
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• pp.109-119
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• 1998

Recently pipe-framed greenhouses are widely constructed on domestic farm area. These greenhouses are extremely light-weighted structures and so are easily damaged under strong wind due to the lack of uplift resistance of foundation piles. This experiment was carried out by laboratory soil tank to investigate the displacement be haviors of cylindrical pile foundations according to the uplift loads. Tested soils were sampled from two different greenhouse areas. The treatment for each soil type are consisted of 3 different soil moisture conditions, 2 different soil depths, and 3 different soil compaction ratios. Each test was designed to be repeated 2 times and additional tests were carried out when needed. The results are summarized as follows : 1. When the soil moisture content are low and/or pile foundations are buried relatively shallow, ultimate uplift capacity of foundation soil was generated just after begining of uplift displacement. But under the high moisture conditions and/or deeply buried depth, ultimate up-lift capacity of foundation soil was generated before the begining of uplift displacement. 2. For the case of soil S$_1$, the ultimate uplift capacity of piles depending on moisture contents was found to be highest in optimum moisture condition and in the order of air dryed and saturated moisture contents. But for the case of soil S$_2$, the ultimate uplift capacity was found to be highest in optimum moisture condition and in the order of saturated and air dryed moisture contents. 3. Ultimate uplift capacities are varied depending on the pile foundation soil moisture conditions. Under the conditions of optimum soil moisture contents with 60cm soil depth, the ultimate uplift capacity of pile foundation in compaction ratio of 80%, 85%, and 90% for soil 51 are 76kg, 115kg, and 155kg, respectively, and for soil S$_2$are 36kg, 60kg, and 92kg, respectively. But considering that typical greenhouse uplift failure be occurred under saturnted soil moisture content which prevails during high wind storm accompanying heavy rain, pile foundation is required to be designed under the soil condition of saturated moisture content. 4. Approximated safe wind velosities estimated for soil sample S$_1$and S$_2$are 32.92m/s and 26.58m/s respectively under the optimum soil condition of 90% compaction ratio and optimum moisture content. But considering the uplift failure pattern under saturated moisture contents which are typical situations of high wind accompanying heavy rain, the safe wind velosities for soil sample S$_1$and S$_2$are not any higher than 20.33m/s and 22.69m/s respectively.

• 한국공간구조학회논문집
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• 제20권3호
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• pp.99-106
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• 2020

If an excessive displacement occurs in the base isolation system, the structure will be damaged due to overturning of the upper structure. In this study, we analyze the behavior of base isolation by applying earthquake to base isolation with anti-uplift device. In the case of structures that generate horizontal reaction forces such as arch structures, horizontal reaction forces must be considered in the design of the base isolation and structural members. And anti-uplift device for preventing the excessive displacement of the base isolation system is needed.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.125-128
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• 2002

The uplift capacity and displacement of an earth anchor for improving the wind resistance of the 1-2W type plastic film pipe on greenhouse was tested using the steel circular vertical earth anchor with various diameters and embedded depths (L) in dry sand. The diameter (B) of the model anchor is 90mm, 120mm, 150mm, respectively. The model tests were performed embedded depth ratios (L/B) ranging from $1{\sim}3$ in loose density. In the case of diameter 90mm, as the uplift loading increased, the uplift capacity also increased until the loading was reached to ultimate uplift capacity. After that, the uplift capacity was continually increased or decreased until the experiment was finished. In general, the ultimate uplift capacity was different depending upon the anchor diameter and embedded depth ratios.