• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.277-284
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• 2000

Using the large diameter (D ＝ 2,500mm, L ＝ 40m) batter steel pipe piles, designed as compression piles but used as reaction piles during the static compression load test of socketed test piles (D ＝ 1,000mm, L ＝ 40m), static pile load tests for large diameter instrumented rock-socketed piles were performed. The reaction steel pipe piles were driven 20m into the marine deposit and weathered rock layer and then l0m socketed with reinforced concrete through the weathered rock layer and into hard rock layer. Steel pipe and concrete in the steel pile part, and concrete and rebars in the socketed parts were instrumented to measure strains in each part. The pullout amounts of reaction pile heads were also measured with LVDT. During the static pile load test, total compressional load of about 20MN was loaded on the head of test piles, but load above 20MN was not loaded due to lack of loading capacity of loading system. Over the course of the study, maximum pullout amount up to 7mm was measured in the heads of reaction piles when loaded op to 10MN and 1mm of pullout amount was measured. More than 85% of pullout load was transfered in the residual weathered rock layer and about 10% in the soft rock layer, which was somewhat different transfer mechanism in the static compressional load tests.

• 콘크리트학회논문집
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• 제12권4호
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• pp.31-40
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• 2000

This study aims to improve serviceability of concrete by inducing chemical prestress with the application of expansive additives for concrete. For this purpose, material tests and 4 point-bending tests of RC slabs were performed to verify the effect of expansive additives on the concrete. and the critical aspects of the structural behavior were investigated. The results of the material tests show that the optimal proportion of expansive additives is 13% of total cement weigth and the properties of expansive concrete in that proportion are the same as those of plain concrete. Both the experimental cracking load and service load of the expansive concrete slabs are increased in comparison with those of the plain concrete. In addition to the above results, the deflection of expansive concrete is smaller than that of plain concrete, and permanent strains resulting from cyclic load are decreased. It can be concluded that the use of expansive additives to induce chemical prestress in RC slabs greatly improves the serviceability.

• 한국해양공학회지
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• 제13권1호통권31호
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• pp.94-104
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• 1999

In order to evaluate the performance of axially of laterally loaded piles experimentaly, pile load tests can be carried out at the site Otherwise stress analyses or subgrade reaction analyses can solve the problem. In this study, stress analysis using FLAC code and subgrade reaction analyses using load transfer curves recommended by API(1993) were performed consistently on the basis of a result of site investigations, and the result of analyses was compared with the measured. As a result the behavior of pile heads was analyzed accurately for both axially and laterally loaded tests. Furthermore axially transferred loads were calculated appropriately for the measured and axial loads were transferred mainly mainly by the frictional resistance rather than by the tip resistance. Consequently, it can be commented that both analysis methods of soil-pile systems are applicable at teh objective site and that solutions may be more accurate if material properties from the site investigation are more explicit.

• 한국안전학회지
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• 제9권1호
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• pp.127-133
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• 1994

In this thesis, the fracture tests were performed on a series of reinforced concrete to investigate the variation of strength and the fracture safety of reinforced concrete structures. The specimens were of the same rectangular cross-section, of effective height 24cm and width 30cm and their span was 330cm. The three point loading system is used in the fracture tests. In these tests, the yield load, the ultimate load, the flexural strain and the mid-span displacement were detected. According to the results of these tests, the fracture behavior of reinforced concrete structures can be summarized as the follows : There Is no difference between the singly and doubly reinforced rectangular beams before the yield load. But from the yield load up to the ultimate load, the mid-span displacement of the singly reinforced rectangular beams are about two times larger than those of the doubly reinforced rectangular beams, The fracture energy of the doubly reinforced rectangular beams are one and half times compared to that of the singly reinforced rectangular beams. Based on the above investigation, it could be concluded that the doubly reinforced rectangular beam is more efficient to resist the brittle fracture than the singly reinforced rectangular beam.

• 한국정밀공학회지
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• 제17권1호
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• pp.204-208
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• 2000

An approximate similarity theory has been applied to predict the forming load of non-axisymmetric forging of aluminum alloys through model material tests. The approximate similarity theory is applicable when strain rate sensitivity, geometrical size, and die velocity of model materials are different from those of real materials. Actually, the forming load of yoke, which is an automobile part made of aluminum alloys(Al-6061), is predicted by using this approximate similarity theory. Firstly, upset forging tests are have been carried out to determine the flow curves of three model materials and aluminum alloy(Al-6061), and a suitable model material is selected for model material test of Al-6061. And then hot forging tests of aluminum yokes have been performed to verify the forming load predicted from the model material, which has been selected from above upset forging tests. The forming loads of aluminum yoke forging predicted by this approximate similarity theory are in good agreement with the experimental results of Al-6061 and the results of finite element analysis using DEFORM-3D.

• 한국지반환경공학회 논문집
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• 제8권6호
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• pp.61-68
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• 2007

본 연구에서는 비등방경화 구성모델을 이용하여 반복재하 평판재하시험에 대한 유한요소해석을 수행하였다. 이 때 구성모델은 ABAQUS 코드에서 제공하는 사용자 서브루틴에 적용하였다. 평판재하시험의 해석결과를 이용하여 영계수와 변형률을 역계산 하였으며 입력된 변형계수와 비교한 결과 적절하게 계산할 수 있는 것으로 판단되었다. 이러한 기법을 토대로 평판재하시험 사례에 대한 적용을 수행하였다. 이로부터 변형률에 따른 변형계수의 변화를 반복재하 평판재하시험 결과로부터 실용적으로 획득하는 것이 가능하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1117-1124
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• 2008

In This paper, load-settlement curves that obtained from 11 sites were analyzed. At all tests, the load is applied until apparent failure is observed. The validity of the ultimate and yield load estimation method and load calculated from the settlement criterion was investigated through comparison with the measured data. The result indicated that B. Hansen 80% criterion and Stability Plot in ultimate loading decision law almost have been regared as same by comparing measured date and ultimate bearing capacity decided in depending yield loading decision law from 13% to 46% difference have taeyaeen came out when measured data and Davisson was compared, and S-log t from 5% to 41% log P-log S from 14% to 50% difference have been came out. When Settlement standard and measured data was compared difference had been came out about 3% in total settlement 0.1D criterion and from 12% to 35% difference had been came out in net settlement.

• Geomechanics and Engineering
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• 제10권2호
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• pp.155-174
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• 2016

A total of 104 laboratory model tests on a square footing subjected to eccentrically inclined loads supported by sand reinforced with randomly distributed polypropylene fibers were conducted in order to compare the results with those obtained from unreinforced sand and with each other. For conducting the model tests, uniform sand was compacted in a test box at one particular relative density of compaction. The effect of percentage of reinforcement used, thickness of the reinforced layer, angle of inclination of load to vertical and eccentricity of load applied on various prominent factors such as ultimate load, vertical settlement, horizontal deformation and tilt were investigated. An improvement in ultimate load, vertical settlement, horizontal deformation and tilt of foundation was observed with an increase in the percentage of fibers used and thickness of reinforced sand layer under different inclinations and eccentricities of load. A statistical model using non-linear regression analysis based on present experimental data for predicting the vertical settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) of square footing on reinforced sand at any load applied was done where the dependent variable was predicted settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) respectively.

• 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.

• 한국안전학회지
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• 제18권1호
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• pp.81-88
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• 2003

Recently, pile foundations were constructed in rough or soft ground than ground of well condition thus it is important that prediction of ultimate bearing capacity and calculation of proper safety factor applied pile foundation design. This study were performed to dynamic loading tests for the thirty two piles at four different construction sites and selected pile at three site were performed to static loading tests and then compare with measured value and value of static and dynamic loading tests. The load-settlement curve form the dynamic loading tests by CAPWAP was very similar to the results obtained from the static load tests. Based on dynamic and static loading tests, the reliability of pile-driving formula were analyzed and then suggested with proper safety factor for prediction of allowable bearing capacity in this paper.