• Journal of the Korean Geotechnical Society
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• v.35 no.6
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• pp.39-48
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• 2019

This study investigated the lateral behavior of monopile embedded in the dry sand through cyclic lateral loading test using a centrifuge test. The sand sample for the experiment was the dry Jumunjin standard sand at 80% relative density and the friction angle of $38^{\circ}$. In the experimental procedure, firstly, it was determined the static lateral bearing capacity by performing the static lateral loading test to decide the cyclic load. This derived static lateral bearing capacity values of 30%, 50%, 80%, 120% were determined as the cyclic lateral load, and the number of cycle was performed 100 times. Through the results, the experiment cyclic p-y curve was calculated, and the cyclic p-y backbone curve by depth was derived using the derived maximum soil resistance point by the load. The initial slope at the same depth was underestimated than API (1987) p-y curves, and the ultimate soil resistance was overestimated than API (1987) p-y curves. In addition, the result of the comparison with the suggested dynamic p-y curve was that the suggested dynamic p-y curve was overestimated than the cyclic p-y backbone curve on the initial slope and soil resistance at the same depth. It is considered that the p-y curve should be applied differently depending on the loading conditions of the pile.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.329-338
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• 2019

In this study, we analyze consumer preferences based on the agricultural box scheme attributes, and make a suggestion for business revival. We estimate the marginal willingness to pay (MWTP) for box scheme attributes using a choice experiment. Attributes include the bundle method, the delivery method, and price. To select an efficient model for statistical analysis, we evaluate the conditional logit model, heteroscedastic extreme value model(HEV model), multinomial probit model, and mixed logit model under different assumptions. The results of these four models show that the bundle method, the delivery method, and price are statistically significant in explaining the probability of participation in a box scheme. The results of likelihood ratio tests show that the heteroscedastic extreme value model is the most appropriate for our survey data. The results also indicate that MWTP for a change from fixed type to selection type is KRW 7,096.6. MWTP for a change from parcel service to direct delivery and cold-chain delivery are KRW 3,497.5 and KRW 7,532.7, respectively. The results of this study may contribute to the government's local food policies.

• Geotechnical Engineering
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• v.14 no.5
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• pp.163-172
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• 1998

To study the carrying capacity behavior of pile, dynamic pile testis and static load tests were carried out on two instrumented piles during and some time after pile driving. Cone Penetration Test( CPT) and Standard Penetration Test(SPT) were also performed at the test site before pile tests to investigate the relationship between unit skin friction of piles and cone tip resistance values and SPT N values. Total static capacity of pile reached the ultimate stage at the pile head settlement of about 0.055D (D : Pile diameter), at which skin friction of Pile already Passed the maximum value, but the end bearing was still increasing with the pile head settlement. The carrying capacity of pile increased in the form of natural logarithmic function with the time after pile driving. The increase in skin friction with time was very substantial the increase in skin friction 40 days after pile driving was 4.6 times of that determined during pile driving. The contribution of skin friction to the total capacity twas insignificant in the beginning, but became substantial 40 days after pile driving. This implies that the tested pile initially responded as an end bearing pile and later behaved as a friction pile. It was also noted that unit skin friction of pile might be ielated to cone tip resistance values(q.) and SPT N values, though the coefficient of this relationship might differ from one soil group to another and was somewhat greater than the value used in the design practice of Korea.

• Geotechnical Engineering
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• v.10 no.2
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• pp.25-40
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• 1994

In order to investigate behavior of lateral flow by plasticity of soils and construction control due to it, in the case of unsymmetrical surcharge load on the soft soils, we examine the existing theoretical background, and compared and analysed the experimental results by model test. After model test fabricated by model test apparatus, which made full remolding samples of soft soils, we observed the state of behavior for deformation with increasing load step to constant time interval. The critical surcharge and ultimate capacity showed tendency to approach to the proposed value of Jaky and Meyerhof, and the lateral flow pressure of which the maximum value was acted on the depth calculated by z/H=0.26+1.71cu and one third value of the maximum lateral flow pressure acted on the ground surface, approach the trapezoid distribution And maximum lateral flow pressure will be calculated by proposed equation of Hong or simple equation which($\alpha=0.4$) the flow pressure coefficient . of proposed equation by Tschebotarioff exchanged to($\alpha=K_0$) . Basides, the failure surcharge by [(q/$y_m$)-q] and [$S_y-(y_m/S_y)$] showed the smaller than ultimate bearing capacity, especially failure criteria line of control diagram of [$S_y(y_m/S_y)$] will be calculated by following equation. $S_y.=3.15exp[-0.58(y_m/S_y)$

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.64-70
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• 2023

In this study, reliability tests of torsion control expansion anchors according to drill bit diameters were performed. The standard deviation and coefficient of variation of the anchor were reviewed through the tests for each variable, and the results were compared and evaluated with the standard test results. As a result of the reliability test of the M12 and M16 anchors with 1.04 times the drill bit diameter, they were within 20% of the ultimate tensile load permissible standard coefficient of variation. It was found that the pulling-out performance of the anchor installed in the large hole was sufficiently secured. However, it was found to be about 253% and 210% of the design strength, indicating that the pulling performance of the anchor installed in 1.04 times the drill bit diameter was sufficiently secured. As a result of the reliability test of the M12 and M16 anchors with 1.02 times the drill bit diameter, the value of the coefficient of variation of the ultimate tensile load limit was within 20%, which satisfies the test standard. It was shown to be about 136% and 168% of the design strength, indicating that the pulling-out performance of the anchor installed in 1.02 times the drill bit diameter is sufficiently secured.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10C
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• pp.991-999
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• 2006

This paper shows that the support growth of an optimum (minimum mean square-error) scalar quantizer for a Laplacian density is logarithmic with the number of quantization points. Specifically, it is shown that, for a unit-variance Laplacian density, the ratio of the support-determining threshold of an optimum quantizer to $\frac 3{\sqrt{2}}1n\frac N 2$ converges to 1, as the number of quantization points grows. Also derived is a limiting upper bound that says that the optimum support cannot exceed the logarithmic growth by more than a constant. These results confirm the logarithmic growth of the optimum support that has previously been derived heuristically.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.413-420
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• 2011

The test results of high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers, were compared with the prediction results of codes, guidelines and models proposed by researchers. The theoretical calculation based on the ultimate strength method of the KCI and ACI Code underestimated the ultimate moments of FRP bar-reinforced beams without fibers. The models proposed by ACI 544.4R and Campione predicted the ultimate moment capacities inaccurately for the FRP bar-reinforced beam with steel fibers, because these models do not consider the increased ultimate compressive strain of fiber reinforced concrete. Bischoff's deflection model predicted the service load deflections reasonably well, while the deflection model of ACI Committee 440 underestimated the deflection of FRP bar-reinforced beams. Because the ACI 440 expression, used to predict member deflection, cannot directly apply to the beams reinforced with different types of reinforcing bars, an alternative method to estimate the deflections of beams with different types of reinforcing bars using the ACI 440 expression was proposed. In addition, Bischoff's approach for computing deflection was extended to include deflection after yielding of the steel reinforcement in the beams reinforced with steel and FRP bars simultaneously.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.489-499
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• 2009

It is quite difficult to predict the flexural strength of post-tensioned members with unbonded tendons (unbonded posttensioned members, UPT members) because of debonding behavior between concrete and prestressing tendons, which is different from that with bonded tendons. Despite many previous researches, our understanding on the flexural strength of UPT members is still insufficient, and thus, national codes use different methods to calculate the strength, which quite often give very different results. Therefore, this paper reviews various existing methods, and aims at proposing an improved rational strength model for UPT flexural members having better accuracy. Additionally, a database containing a large number of test data on UPT flexural members has been established and used for verification of the proposed flexural strength model. The analysis results show that the proposed method provides much better accuracy than many existing methods including the rigid-body model that utilizes the assumption of concentrated deformation and plastic hinge length, and that it also gives proper consideration on the effects of primary parameters such as reinforcement ratio, loading pattern, concrete strength, etc. Especially, the proposed method also well predicts the ultimate stress of unbonded tendons of over-reinforced members, which are often possible in construction fields, and high strength concrete members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.627-637
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• 2022

To know the magnitudes of extreme floods for various sizes of watersheds, massive streamflow data is fundamentally required. However, small/medium-size watersheds missed streamflow data because of the lack of gauge stations. In this study, the Streamflow Propagation Method (SPM) was applied to generate streamflow data for small/medium size watersheds with no measurements. Based on the generated streamflow data for ungauged watersheds at three different locations (i.e., Chungju Dam (CJD), Seomjin Dam (SJD), and Andong Dam (ADD) watersheds), the scale ranges of extreme floods were evaluated for different sizes of ungauged watersheds by using the specific flood distribution analysis. As a general result, a range of specific floods decreases with increasing watershed size. The distribution of the specific flood in the same size of a watershed possibly depends on the size and topography of the watershed area. The delivered equations were compared to show the relations between the specific flood and sizes of watersheds. In the comparisons of equations, the Creager envelope curve has the higher potential to represent the maximum flood distribution for each watershed. For the generalization of the maximum flood distribution for three watersheds, optimized envelop curves are obtained with lower RMSE than that of Creager envelope curve.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.398-398
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• 2021

섬진강은 한국 주요 5대강 중 하나로 유량 변동계수가 가장 크다. 이로 인해, 극심한 가뭄이나 홍수의 발생 확률이 높을 뿐만 아니라, 가뭄에서 홍수 또는 홍수에서 가뭄으로 갑작스러운 극한 수문 기상 변화가 일어날 수 있다. 수자원의 안정적인 확보와 수재해로 인한 피해를 최소화하기 위한 수자원 관리와 장기적 수문분석이 필요하다. 이에 본 연구에서는 섬진강 유역의 수문 관측소(56개)에서 10년 이상 장기 관측된 일유량 자료(1997년~2020년)를 이용하여 비모수 검정 방법을 통한 추세 분석과 변동점을 탐색하였다. 우선, 일유량 관측 자료를 이용하여 누락된 일유량 관측값으로 생겨날 수 있는 불확실성을 배제하기 위해 관측 기간 중 누락된 일유량 관측값들의 월별 비율을 조사하였다. 그리고 월별 일유량 관측값 누락이 없는 관측소들의 월평균 하천 유량 값으로 연평균 하천 유량 값을 계산하였다. 관측 기간 동안 결측된 값이 없는 28개의 관측소를 대상으로 비모수 검정 방법을 통한 연별 추세 분석(Mann-Kendall Test)과 변동점 탐색(Pettitt Test)을 하였다. 연별 추세 분석 경우 28개의 관측소 중 8개의 관측소에서 통계적으로 의미 있는 추세(신뢰도> 99%)가 탐지되었다. 이들 중 3개의 관측소에서는 증가하는 추세를 보였고 5개의 관측소에서 감소하는 추세가 보였다. 7개의 관측소에서는 통계적으로 의미가 있는 변동점도 탐색되었고 그 변동점이 탐색된 연도는 2011년(4개), 2012년(3개)로 나타났다. 계절적 추세 분석에서는 28개의 관측소 중 각각 봄(MAM) 11개, 여름(JJA) 11개, 가을(SON) 9개, 겨울(DJF) 11개 관측소에서 통계적 추세(신뢰도> 99%)가 탐지되었다. 또한 봄 17개, 여름 7개, 가을 18개, 겨울 18개 관측소에서 변동점이 탐색되었고, 그 연도는 관측소마다 달랐다. 이러한 유량의 추세와 변동점의 원인(기후적/인위적 요소)을 더욱 잘 이해하기 위해, 계절별 유량과 강수량의 상관관계 분석이 연구될 필요가 있다. 이러한 장기 수문기후학적 추세와 변동성에 대한 이해는 농업이 중요한 섬진강 유역의 수자원 관리와 기후변화에 선제대응 할 수 있는 기초를 마련할 것이다.