• 한국농공학회논문집
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• 제63권6호
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• pp.17-26
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• 2021

Greenhouses have been damaged due to the uplift pressure from strong wind, for which rebar piles are often installed near the greenhouse to resist the pressure. For the effective design of rebar piles, it is necessary to access the shear strength of soil on which the greenhouse is constructed. This study experimentally evaluates the shear strength of the soil beneath the greenhouse. Four soil samples were collected from four agricultural sites, and prepared for testing with 75, 80, 85, and 90% compaction rates. One-dimensional unconfined compression test (UC), consolidated-undrained triaxial test (CU), and resonant column test (RC) were performed for the evaluation of shear strength and shear modulus. Generally, the higher shear strength and modulus were observed with the higher compaction rates. In particular, the UC shear strength increases with the increase of #200 sieve passing rate. Resulting from the CU test, the sample with the most of coarse soil had the highest friction angle, but the variation is small among samples. Resulting from the CU and RC tests, the ratio of maximum shear modulus with the major principle stress at failure was the higher at the finer soil. The ratio was two to three times greater than the ratio from the standard sand. This indicates that the shear strength is lower for the fine soil than the coarse soil at the same shear modulus. The results of this study will be a useful resource for the estimation of the pull-out strength of the rebar pile against the uplift pressure.

• 한국재난정보학회 논문집
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• 제15권4호
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• pp.590-596
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• 2019

연구목적: 직접전단시험의 문제점 중에 하나인 시험시편의 크기효과에 대하여 모래시료를 대상으로 실험적 연구를 수행하였다. 연구방법: 우리나라를 대표하는 모래인 주문진 표준사를 연구 대상으로 사용하였다. 상대밀도 50%, 60%, 70%, 80%에 대한 전단강도를 분석하기 위하여 대형직접전단시험을 수행한 후 소형직접전단기의 시험결과와 비교분석을 수행하였다. 연구결과: 상대밀도가 촘촘한(dense) 영역에서는 소형전단시험기의 내부마찰각이 비교적 큰 경향이 있는 것으로 분석되었다. 상대밀도가 중간(medium)정도의 영역에서는 대형전단시험기의 결과가 비교적 큰 경향이 있는 것으로 분석되었다. 결론: 모래흙에서 직접전단시험의 시료에 대한 크기 효과는 비교적 크지 않은 것으로 분석되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.569-576
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• 2000

This study performs a series of Triaxial Compression Test for clay-sand composite specimens changing area replacement ratio. Purpose of the test is to conform the propriety of weighted average method in estimating shear strength of the composite ground. The test results show that measured values of shear strength of composite specimens are larger by 20∼30% than those from estimation using the current weighted average method. It is thought that the differences are from pseudo-overconsolidation behavior of composite specimens.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.201-207
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• 2002

An advanced fiber sheet has been widely used for strengthening of the concrete structures due to its excellent properties such as high strength and light weight. Bond strength is very important in strengthening the concrete structures using an advanced fiber sheet. This research examines the bond behavior between fiber sheet and concrete, investigates the bond strength by the direct pull-out test and the tensile-shear test. To obtain the tensile-shear strength a double-face shear type bond test is conducted. The primary test variables are the types of concrete surface roughness (disk-grinding/chipping) and retrofitting methods (bonding/injection). Thirty specimens were tested to evaluate the bond strength. It is shown that the average bond strength between fiber sheet and concrete by the direct pull-out test and the tensile-shear test is $22.3{\sim}23.1kgf/cm^2$ $17.92{\sim}19.75kgf/cm^2$, respectively.

• 한국해양공학회지
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• 제25권3호
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• pp.34-39
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• 2011

This study investigated the shear and CBR characteristics of dredge soil-bottom ash-waste tire powder-mixed lightweight soil, which was developed to recycle dredged soil, bottom ash, and waste tire powder. Test specimens were prepared with various contents of waste tire powder ranging from 0 to 100% at 50% intervals by the weight of the dry dredged soil. Several series of triaxial compression tests and CBR tests were conducted. The shear strength characteristics of the lightweight soil were compared using two different shear tests (triaxial compression test and direct shear test). The experimental results indicated that the internal friction angle of the lightweight soil obtained by the direct shear tests was greater than that by the triaxial shear tests. However, the cohesion value obtained by the triaxial shear tests was greater than that by the direct shear tests. The CBR value of the lightweight soil decreased from 35% to 15% as waste tire powder content increased.

• Advances in concrete construction
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• 제13권3호
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• pp.265-279
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• 2022

The roughness of substrate concrete interfaces before new concrete placement has a major effect on the interface bond behaviour. However, there are challenges associated with the consistency of the final roughness interface prepared using conventional roughness preparation methods which influences the interface bond performance. In this study, five quantitative interface roughness textures with different roughness tooth angles, depths, and tooth distribution were created to ensure consistency of interface roughness and to evaluate the bond behaviour at a precast and new concrete interface using the splitting tensile test, slant shear test, and double-shear test. In addition, smooth interface specimens and two separate the pitting interface roughness were also utilized. Obtained results indicate that the quantitative roughness has a very limited effect on the interface tensile bond strength if no extra micro-roughness or bonding agent is added at the interface. The roughness method however causes enhanced shear bond strength at the interface. Increased tooth depth improved both the tensile and shear bond strength of the interfaces, while the tooth distribution mainly influenced the shear bond strength. Major failure modes of the test specimens include interface failure, splitting cracks, and sliding failure, and are influenced by the tooth depth and tooth distribution. Furthermore, the interface properties were obtained and presented while a comparison between the different testing methods, in terms of bond strength, was performed.

• 한국항해항만학회지
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• 제37권2호
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• pp.155-163
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• 2013

이 연구에서는 전단하중을 받는 부유식 콘크리트 구조물 모듈 접합부의 구조거동 실험연구를 수행하였다. 모듈 접합부 전단키의 균열 양상, 전단거동 및 전단강도를 파악하였다. 전단강도의 영향을 파악하기 위해 전단키의 경사각도, 횡방향 구속응력 및 콘크리트의 압축강도 등을 실험변수로 고려하였다. 전단키의 경사각도가 증가함에 따라 접합부의 전단강도가 증가하였다. 또한, 구속응력이 증가함에 따라 전단키의 전단강도가 증가하였다. 실험변수에 따른 전단거동 실험결과를 토대로 접합부의 전단강도 평가식을 제안하였으며, 제안식에 의한 전단강도 예측값은 실험값에 근접하는 것으로 나타났다.

• 터널과지하공간
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• 제21권3호
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• pp.181-191
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• 2011

단층대, 파쇄대 또는 풍화대가 발달한 암반은 실내시험을 위한 시료 성형이 어렵다. 기존에 현장에서 수행된 직접전단시험은 갱도 내벽의 수직반력을 이용하여 수행되었다. 이 연구에서 개발된 현장직접전단시험기는 터널내부 또는 노천의 현장상태 암반에서 시험을 수행할 수 있다. 현장직접전단시험기의 주요 구성은 전단하중 반력판 및 하중전달판, 유압실린더 시스템, 로드셀, 다단계 전단상자, 전단상자 고정장치, 수직하중 반력판 및 하중전달판, 마찰저항 감소용 롤러 등이다. 공시체는 각주형의 블록으로 최대 크기는 $400{\times}400{\times}460$ mm이며 현장에서 형성하는 방법 및 절차가 제시되었다. 개발된 시험기의 현장적용성 평가를 위하여 연구지역에 대한 지질공학적 조사 분석 연구를 통하여 성능시험을 위한 공시체 형성에 적합한 위치가 선정되었다. 현장적용 결과 개발된 현장용 시험기는 암석의 강도 및 변형과 관련하여 필요한 대부분의 정보를 제공할 수 있는 성능을 확보하였음을 확인하였다.

• Steel and Composite Structures
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• 제26권6호
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• pp.759-769
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• 2018

This paper studies shear and tensile behaviors of headed stud connectors in double skin composite (DSC) structure. Firstly, 11 push-out tests and 11 tensile tests were performed to investigate the ultimate shear and tensile behaviors of headed stud in DSC shear wall, respectively. The main parameters investigated in this test program were height and layout of headed stud connectors. The test results reported the representative failure modes of headed studs in DSC structures subjected to shear and tension. The shear-slip and tension-elongation behaviors of headed studs in DSC structures were also reported. Influences of different parameters on these shear-slip and tension-elongation behaviors of headed studs were discussed and analyzed. Analytical models were also developed to predict the ultimate shear and tensile resistances of headed stud connectors in DSC shear walls. The developed analytical model incorporated the influence of the dense layout of headed studs in DSC shear walls. The validations of analytical predictions against 22 test results confirmed the accuracy of developed analytical models.

• Geomechanics and Engineering
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• 제37권6호
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• pp.615-627
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• 2024

Direct simple shear test is an effective method to measure strength and deformation properties of soil. However, existing direct simple shear apparatus have some shortcomings. The paper has developed a novel dual stress/strain-controlled direct simple shear apparatus. The novel apparatus has the following advantages: A rectangular specimen is used that effectively avoid common issues associated with conventional cylindrical specimens, such as specimen tilting. The utilization of deformation control rods ensures a uniform shear deformation of the specimen. Vertically integrated force transmission structure is improved that avoids issues arising from changes in pivot points due to lever tilting. Incorporating this novel direct simple shear apparatus, shear strength and shear creep tests of clay were performed. Shear strength parameters and shear creep behaviors are analyzed. The results of these experiments show that the novel apparatus can measure accurately the shear rheological properties of soil. This study provides strong guidance for studying the mechanical properties of soil in engineering practice.