• 한국한의학연구원논문집
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• 제14권3호
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• pp.103-111
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• 2008

Recently, skin diagnosis has been suggested as a promising tool for discrimination of Sasang Constitution, reported by examining the skin characteristics such as thickness, stiffness, slip, and skin textures like wrinkles and furrows. However, the works had a limitation in that clinical decision on the skin characteristics was made by relying upon oriental medicine doctors' subjective sense of touch. In order to objectify the skin diagnosis and claim its efficacy on the discrimination of the Sasang Constitutions, it is necessary to demonstrate its discrimination capability by providing numerical values in terms of physical quantities obtained from measurements using today's sensors and equipment technologies, which motivated this work as a priliminary step towards objectification of skin diagnosis. The skin characteristics focused in this work is the slip property of the back-hand skin that has been exploited using the dynamic friction measurement system. First, curved geometric effects of the back-hand skin on the measured lateral/vertical force signals were estimated using the artificially designed silicon coated structures, which led to a suggestion on a quality controlled experimental design based upon a empirical analysis model. Second, the experimental design thus suggested has been applied to the measurement of dynamic friction coefficients for two healthy male subjects of Taeumin (TE) and Soyangin (SY), respectively. The result shows that the dynamic friction coefficient is less for the SY subject than for the TE subject around the area of the skin used for diagnosis by the oriental medicine doctor, implying the TE subject's skin is more slippery than the SE subject's that is consistent with the oriental medicine doctor's diagnosis. Hopefully, this work can provide guidelines for obtaining quality data in friction measurement to be collected for discussion on the efficacy of the skin diagnosis and its objectification through statistical analysis.

• 사상체질의학회지
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• 제22권4호
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• pp.20-29
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• 2010

1. Objectives Our goal is to observe the feasibility of constitution discrimination from computing quantitative roughness index from dynamic friction coefficients and their gradients with the measurement device of skin friction with 3-Axis load cell sensor. 2. Methods In the traditional Korean medicine, skin diagnosis is one of the examination methods to discriminate Sasang constitution since it was known that Tae-eumin has rough skin, and Soyangin has smooth one. It is based on the skin roughness on the back of one's hand for the discrimination. The measurement device of skin friction with 3-axis load cell sensor has been developed in order to provide quantitative skin roughness through dynamic friction coefficients. The effective interval of the coefficients is obtained from the automatic sampling algorithm to use their curvature and slope. Then, Fisher's discriminant function of them makes the discrimination. 3. Results The success rate of extracting the effective interval was about 90% and the discriminant accuracy between Tae-eumin and Soyangin was 70% and 68% for men and women, respectively. The entire methods showed the possibility to distinguish between Tae-eumin and Soyangin by using stochastic properties of roughness index, which can make the entire system to include the measurement, the computation of the roughness index and the discrimination of constitution automatical. 4. Conclusions The measurement device, the automatic sampling algorithm of dynamic friction coefficients and the constitution discrimination algorithm were developed, respectively, and their combination can become the serial and automatic procedure for quantitative and objective skin diagnosis, which mimics the movement of the Oriental medical doctors' skin diagnosis. It can be applied to healthcare as well as the diagnosis of constitution in a u-Health system soon.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1269-1278
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• 2006

These days the construction of extra-long piles increases. It is not unusual to install piles whose length exceed 45m. In such cases, the estimated value of negative skin friction becomes larger, often larger than the design load. In order to be sure of the safety of the super structure, the magnitude of the positive skin friction and the base bearing capacity should be known. In practice dynamic pile loading tests using PDA is the only possible measure to meet this requirement. However the analysis of dynamic pile loading test for such extra-long piles requires a thorough understanding of the pile-soil behaviour. In this paper, a new method to evaluate the positive skin friction and end bearing capacity from the normally performed PDA test is proposed. The proposed method was verified by performing specially designed pilot testings.

• 한국산학기술학회논문지
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• 제14권10호
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• pp.5268-5273
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• 2013

진동타입기에 의해 시공되는 말뚝 해석을 위해 해석기법을 개발하고 진동타입기의 사하중 크기 변화에 따른 해석결과를 분석하였다. 주면마찰에 대한 하중전이곡선은 사하중이 감소함에 따라 연직하향으로 이동하는 결과를 보였다. 사하중이 감소함에 따라 주면마찰에 대한 하중전이곡선의 형상은 점점 뚜렷한 코일 형상을 띄었다. 선단저항의 크기는 사하중의 크기에 큰 영향을 받지 않음을 알 수 있었으며 선단저항에 대한 하중전이곡선의 형상은 주면마찰에 대한 하중전이곡선에서와 마찬가지로 사하중이 감소함에 따라 점점 뚜렷한 코일 형상을 띔을 알 수 있었다. 사하중이 증가함에 따라 연직변위도 크게 계산되었으며 시간에 따른 연직변위의 형상에 있어서는 사하중이 감소함에 따라 마루와 골이 점점 뚜렷해지는 파형을 보였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.249-258
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• 1999

Dynamic load and static load tests are performed on steel pipe piles and concrete piles at five construction sites in highway to compare the difference of load bearing mechanisms. At each site, one steel pile is instrumented with electric strain gages and dynamic tests are performed on the pile during installation. Damages of strain gages due to the installation are checked and static test is performed upon the same pile after two or seven days as well. It shows that load transfer from side friction to base resistance behaves somewhat differently according to the results of load-settlement analysis obtained from PDA and static load test. Initial elastic stage of load settlement curves of two load tests is almost similar. But after the yielding point, dynamic resistance of pile behaves more stiffer than static resistance, thus, dynamic load test result might overestimate the real pile capacity compared with static result. Analysis of gage readings shows that unit skin friction increases exponentially with depth. The skin friction is mobilized at the 1∼2m above the pile tip and contributes to the considerable side resistance. Comparison of side and base resistances between the measured value and the calculated value by Meyerhof's bearing capacity equation using SPT N value shows that the calculated base resistance is higher than the measured. Therefore, contribution of side resistance to total capacity shouldn't be ignored or underestimated. Finally, based upon the overall test results, a construction control procedure is suggested.

• 한국지반공학회논문집
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• 제21권1호
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• pp.93-103
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• 2005

대구경 현장타설말뚝에 대하여 하중전이 측정을 수반한 정재하시험, 동재하시험 및 유한차분해석을 수행하여 주면 마찰력 거동특성에 대한 연구를 실시한다. 주면 마찰력은 말뚝과 지반의 상대변위와 직접적으로 관계되므로 임의의 심도에서 측정한 말뚝의 하중전이량과 유한차분해석에 의한 주면지반의 변위와 응력을 이용하여 거동특성을 분석한다. 하중전이측정결과에 의하면 현장타설말뚝 주면을 따라 발휘되는 극한단위주면 마찰력은 중간 깊이인 모래자갈층과 자갈층 상부에서 먼저 나타난다. 또한 동일한 현장타설말뚝에 대하여 동재하시험과 정재하시험을 실시한 결과 주면 마찰력과 선단지지력의 거동특성이 상이하게 평가되었으며, 그 차이점에 대하여 논의한다.

• 한국지반공학회지:지반
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• 제9권1호
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• pp.31-44
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• 1993

말뚝이 설치되는 동안과 하중이 재하되는 동안에 유발되는 관내토의 거동과 관내토가 개단 말뚝의 지지력에 미치는 영향, 그리고 관내토의 하중전이 메카니즘 등을 알아보기 위하여, 개단말뚝의 단면부에 작용하는 지지력과 관내토에 의한 지지력 및 외주면마찰력을 분리하여 측정할 수 있도록 제작된 모형 개단강관말뚝과 압력조절이 가능한 토조를 이용하여 모래지반을 대상으로한 모형말뚝실험을 실시하였다. 실험결과로부터, 개단말뚝의 폐색정도는 폐색길이비(PLR)보다는 특정회수율(${\gamma}$)에 의하여 더 정화히 성의될 수 리음을 알 수 있으며, 내주면마찰력의 대부분은 말뚝 선단부로부터 말뚝내경의 3배까지의 영역에 존재하는 관내토에 의하여 발생되는 것으로 나타났다. 또한 전체 지지력에서 내주면마찰력이 차지하는 비율은 외주면마찰력이 차지하는 비율보다 상당히 크기 때문에, 개단말쪽의 지지력 산정시 내주면마찰력은 필수적으로 고려되어야 한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.307-314
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• 2001

The bearing capacity of drilled shafts that take excavation by Percussion Rrotary Drilling(PRD) into consideration was evaluated using static and dynamic pile load tests. The emphasis was on quantifying the allowable bearing capacity and point load-transfer at the pile tip on seven instrumented steel piles. Of the seven instrumented piles, five piles are placed to the bottom of the excavation by rotary and pushing into the final depth of the excavation, as opposed to the two driven piles. Based on the results obtained, it is shown that the skin friction mobilized by PRD is much greater than point resistance, whereas in driven piles, the point resistance is greater than skin friction. It is also found that much greater pile capacity was proved in the case of drilled shafts, compared to the driven piles and thus, the excavation by rotary drilling gives reliable pile capacity required to design axially loaded piles.

• 한국지반공학회지:지반
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• 제14권5호
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• pp.163-172
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• 1998

말뚝의 지지력 거동을 연구하기 위하여 말뚝 제작시 다수의 변형률계를 설치한 2본의 말뚝들에 대하여 항타시에 그리고 항타후 소정의 시간이 경과된 시점에 동재하시험과 정재하시험을 몇 차례 수행하였다. 콘관입저항값 그리고 표준관입저항값과 말뚝의 단위 주면마찰력과의 관계를 규명하기 위해 재하시험전에 시험지반에 대하여 론관입시험과 표준관입시험도 실시하였다. 지지력과 두부침하량 관계를 살펴보면, 0.055D(D: 직경)의 두부침하량에서 전체지지력이 극한에 도달하였고, 이 때에 주면마찰력은 극한간에 도달했으나, 선단지지력은 계속 증가하는 것으로 나타났다. 말뚝의 지지력은 항타후 시간이 경과함에 따라 자연대수함수로 증가하였으며, 지지력 성분중 주면마찰력 성분이 항타한 후 40일 경과한 시점에 초기값의 4.6배 정도로 현저하게 증가하였다. 지지력 거동에 대한 시간경과의 영향을 보면, 시험말뚝들은 초기항타시에는 선단지지말뚝으로 거동하다가 시간이 경과하면서 주면마찰 말뚝으로 거동이 변화되었음을 관찰할 수 있었다. 단위 주면마찰력은, 토질분류에 따라 다르지만, 콘관입저항칼(q.)과 표준관입저항값(N)과 일정한 관계를 갖는 것으로 나타났으며, 관계상수는 현재 국내에서 사용하고 있는 간보다 큰 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 봄 학술발표회 논문집
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• pp.145-154
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• 1996