• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.455-465
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• 2008

In this study, the load distribution and deformation of rock-socketed drilled shafts subjected to axial load are investigated based on small scale model tests. In order to analyze the effects of major influencing factors of end bearing capacity, Hoek-cell triaxial tests were performed. From the test results, it was found that the initial slope of end bearing load transfer (q-w) curve was highly dependent on rock mass modulus and pile diameter, while the ultimate unit toe resistance ($q_{max}$) was influenced by rock mass modulus and the spacing of discontinuities. End bearing load transfer function of drilled shafts socketed in rock was proposed based on the Hoek-cell triaxial test results and the field loading tests which were performed on granite and gneiss in South Korea. Through the comparison with pile load tests, it is found that the load-transfer curve by the present study is in good agreement with the general trend observed by field loading tests, and thus represents a significant improvement in the prediction of load transfer of drilled shaft.

• Geomechanics and Engineering
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• 제29권4호
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• pp.407-420
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• 2022

Embedded piles, which are typically used in Korea, are precast piles inserted into prebored ground with cement paste. Dynamic pile tests tend to underestimate the bearing capacity of embedded piles because of the undeveloped shaft resistance prior to the curing of the cement paste and the insufficient energy transferred after the curing. In this study, a resistance combination method using the base resistance before the cement paste is cured and the shaft resistance after the cement paste is cured is proposed to obtain a combined load-settlement curve from dynamic pile tests. Two pairs of embedded piles with diameters of 600 and 500 mm are installed. Each pair comprises one pile for the dynamic pile test and another pile for the static load test. The shape of the load-settlement curve obtained using the proposed method is similar to that obtained from the static load test. Thus, the resistances evaluated using the proposed method at selected settlements are similar to those obtained from the static load test. This study shows that the resistance combination method may be used effectively in dynamic pile tests to accurately evaluate the bearing capacity of embedded piles.

• 대한전기학회논문지:전력기술부문A
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• 제48권1호
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• pp.22-30
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• 1999

This paper presents an efficient algorithm to estimate the maximum load level for heavily loaded power systems with the load-generation vector obtained by ELD (Economic Load Dispach) and/or short term load forecasting while utilizing the elliptic pattern of the P-e curve. It is well known the power flow equation in the rectangular corrdinate is jully quadratic. However, the coupling between e and f makes it difficult to take advantage of this quadratic characteristic. In this paper, the elliptic characteristics of P-e curve are illustrated and a simple technique is proposed to reflect the e-f coupling effects on the estimation of maximum loadability with theoretical analysis. An efficient estimation algorithm has been developed with the use of the elliptic properties of the P-e curve. The proposed algorithm is tested on IEEE 14 bus system, New England 39 bus system and IEEE 118 bus system, which shows that the maximum load level can be efficiently estimated with remarkable improvement in accuracy.

• 한국조명전기설비학회지:조명전기설비
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• 제9권5호
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• pp.37-40
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• 1995

In this paper, we investigate the daily load curve and yearly lighting hours of general and industrial Korean lighting apparatus. The daily load curve of lighting apparatus shows the peak use at 8 p.m. in general and 10 a.m. in industrial building. The yearly lighting hours are 2,948 hours in general and 4,066 hors in industrial building.

• 대한전기학회논문지
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• 제31권7호
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• pp.1-10
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• 1982

This paper derives the algorithm to estimate the operating cost, its marginal cost, and the reliability indices for the long term planning of power system. Treating the load duration curve and the system in the stochastic sense takes the place of the inverted load duration curve, effective load duration curve, and the numerical integration in the conventional methods. The time and accuracy of computation are substantially improved due to the fact that all expressions are represented by simple analytic form instead of the existing recursive form.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.953-958
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• 2007

To assess the derailment safety of the Samaeul Train, We developed a fleet analysis model and carried out sensitivity analysis of the variables related to derailment factors with ADAMS/Rail computing analysis method. Depending on the variation of the running speed in curve section, derailment coefficient and wheel load reduction rate are high at right side wheels in slow running speed section and low at left side wheel in high running speed. According to decreasing the radius of curve, derailment coefficient and wheel load decreasing rate are increased. Derailment coefficient is proportional to transition curve length and wheel load decreasing rate is constant. Cant value rising causes wheel load deduction rate rising.

• 한국지리정보학회지
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• 제24권3호
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• pp.41-57
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• 2021

본 연구는 대청호 상류에 있는 서화천 유역을 대상으로 SWAT(Soil and Watershed Assessment Tool) 모형을 이용한 수질 관리 대책 적용 및 부하지속곡선(LDC, Load Duration Curve)을 이용한 대책의 효율을 평가하였다. 수질 관리 대책으로는 인공습지, 방치 축분 저감, 비닐하우스 유출량 저감, 생태하천 복원, LID(Low Impact Development) 기술 적용, 점오염원 관리를 적용하였다. 적용된 기술은 부하지속곡선을 통해 유황별 목표 수질 초과율 및 부하량 저감 정도를 이용하여 수질 개선대책의 효율을 평가하였다. 부하지속곡선은 SWAT를 이용하여 장기 유량지속곡선(FDC, Flow Duration Curve)을 만들고 목표 수질을 곱하여 작성하였으며 목표 수질은 서화천 하류에 있는 옥천천 수질 관측지점의 10년간 자료를 사용하여 60분위에 해당하는 값을 목표 수질로 설정하였다. 본 연구를 통하여 여러 가지 수질 대책을 SWAT 모형을 통해 적용 가능성을 확인할 수 있으며 부하지속곡선을 통하여 유황에 따른 시기별 적용 가능성을 검토할 수 있었다.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1270-1279
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• 2002

Residual stress is a dominant obstacle to efficient production and safe usage of device by deteriorating the mechanical strength and failure properties. Therefore, we proposed a new thin film stress-analyzing technique using a nanoindentation method. For this aim, the shape change in the indentation load-depth curve during the stress-relief in film was theoretically modeled. The change in indentation depth by load-controlled stress relaxation process was related to the increase or decrease in the applied load using the elastic flat punch theory. Finally, the residual stress in thin film was calculated from the changed applied load based on the equivalent stress interaction model. The evaluated stresses for diamond-like carbon films from this nanoindentation analysis were consistent with the results from the conventional curvature method.

• Computers and Concrete
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• 제13권3호
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• pp.411-421
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• 2014

A central pullout test was conducted to investigate the bonding properties between high strength rebar and reactive powder concrete (RPC), which covered ultimate pullout load, ultimate bonding stress, free end initial slip, free end slip at peak load, and load-slip curve characteristics. The effects of varying rebar buried length, thickness of protective layer and diameter of rebars on the bonding properties were studied, and how to determine the minimum thickness of protective layer and critical anchorage length was suggested according the test results. The results prove that: 1) Ultimate pull out load and free end initial slip load increases with increase in buried length, while ultimate bonding stress and slip corresponding to the peak load reduces. When buried length is increased from 3d to 4d(d is the diameter of rebar), after peak load, the load-slip curve descending segment declines faster, but later the load rises again exceeding the first peak load. When buried length reaches 5d, rebar pull fracture occurs. 2) As thickness of protective layer increases, the ultimate pull out load, ultimate bond stress, free end initial slip load and the slip corresponding to the peak load increase, and the descending section of the curve becomes gentle. The recommended minimum thickness of protective layer for plate type members should be the greater value between d and 10 mm, and for beams or columns the greater value between d and 15 mm. 3) Increasing the diameter of HRB500 rebars leads to a gentle slope in the descending segment of the pullout curve. 4) The bonding properties between high strength steel HRB500 and RPC is very good. The suggested buried length for test determining bonding strength between high strength rebars and RPC is 4d and a formula to calculate the critical anchorage length is established. The relationships between ultimate bonding stress and thickness of protective layer or the buried length was obtained.

• Geomechanics and Engineering
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• 제15권2호
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• pp.745-754
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• 2018

In the analysis of the effects of rock tunnel blasting vibration on adjacent existing buildings, the model of simplified equivalent load produces higher calculation result of vibration, due to the lack of consideration of the millisecond delay effect. This paper, based on the static force equivalence principle of blasting load, proposes a new determination method of equivalent load of blasting vibration. The proposed method, based on the elastic-static force equivalence principle of stress wave, equals the blasting loads of several single blastholes in the same section of millisecond blasting to the triangle blasting load curve of the exploded equivalent elastic boundary surface. According to the attenuation law of stress wave, the attenuated equivalent triangle blasting load curve of the equivalent elastic boundary is applied on the tunnel excavation contour surface, obtaining the final applied equivalent load. Taking the millisecond delay time of different sections into account, the time-history curve of equivalent load of the whole section applied on the tunnel excavation contour surface can be obtained. Based on Sailing Tunnel with small spacing on Sanmenxia-Xichuan Expressway, an analysis on the blasting vibration response of the later and early stages of the tunnel construction is carried out through numerical simulation using the proposed equivalent load model considering millisecond delay effect and the simplified equivalent triangle load curve model respectively. The analysis of the numerical results comparing with the field monitoring ones shows that the calculation results obtained from the proposed equivalent load model are closer to the measured ones and more feasible.