• The Journal of Engineering Geology
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• v.18 no.2
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• pp.227-232
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• 2008

In this study, the pull out resistance characteristics of an anchor bar to support a spillway installed in a slope are investigated by field tests. The injection materials were a cement mortar and cement milk. Unconfined compression strengths of those materials under several conditions were measured. As the result of compression test, the unconfined compression strengths of the cement mortar and the cement milk have positive proportional relation-ship with the water-cement ratio. They also have negative proportional relationship with increasing the curing time. In the same condition of water-cement ratio and curing time, the unconfined compression strength of cement milk is larger than that of cement mortar. In order to reduce the eccentricity in anchor bar during pull-out test in the field, the installation apparatus was improved by inserting a nut type of steel fixing coupling into the anchor bar. As the result of the pull-out test, the strength modification of cement milk was increased steeply at the early curing time. However, that of cement mortar was increased gradually with passing the curing time. Therefore, the cement milk has to use as the injection material for a prompt construction of anchor bar because the strength modification of cement milk is occurred at the early curing time.

• Journal of the Korean Geotechnical Society
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• v.28 no.1
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• pp.55-66
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• 2012

The load transfer mechanism of hybrid model of soil-nailing and compression anchor is studied in this paper. The hybrid model is composed of an anchor bar (installed at the tip) with two PC strands and a steel bar. It can make active behavior of skin friction by applying the pre-stress. In this paper, the load transfer mechanisms of soil-nailings, compression anchors, and hybrid models, respectively, are obtained from skin friction theory and load transfer theory. Field pullout tests are performed to identify the load transfer mechanism and experimental results are compared with analytical solution. In case of soil-nailings, the tension load is transferred from face to tip, however, in case of compression anchors, the compression load is transferred from tip to face. The experimental behavior of the hybrid model is similar to that of compression anchor when only pre-stress is applied. If the pullout test is performed by simultaneously pulling out the anchor and the nail, the compression load is dominant at the tip and tension load is dominant at the face. The load transfer mechanism of the hybrid model shows the combined behavior of soil-nailings with compression anchors.

• Journal of the Korean Geotechnical Society
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• v.35 no.7
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• pp.29-39
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• 2019

Load distributive compression anchors distribute the compressive stress in the grout and increase the pull-out capacity of the anchor by using multiple anchor bodies. In this anchor type, the spacing between the anchor bodies has a large influence on the stress in the grout. However, there are few researches about the spacing and there are no design standards. Therefore, the effect of the anchor body spacing on the grout stress was analyzed by performing finite element analyses. First, the applicability of the numerical modeling was verified by comparing with field test results of a compression anchor. Then, the parametric study was performed varying soil type, anchor body spacing, and load magnitude. The analysis results showed that the maximum compressive stress in the grout increased at the narrower spacing and the tensile stress developed at the wider spacing. Therefore, the optimum spacing was defined as the spacing, which prevents the superposition of compressive stresses and minimize the tensile stress. Finally, the optimum spacing was proposed according to the soil type and the load magnitude.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.1
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• pp.25-50
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• 2014

In order to identify a load transfer mechanism of ground anchors, the behavior of multi load transfer ground anchor systems was investigated and compared with those of compression type anchors and tension type anchors. Large scale model tests were performed and stress-strain relationships were obtained. The load transfer mechanism of ground anchors was also investigated in the field tests. Finally, numerical analyses to predict the load-displacement relationships of anchors were conducted. It is concluded that the load transfer characteristics of MLT anchors are mechanically much more superior in the pull-out resistance effect than those of existing compression and tension type anchors. From the results of research work, we could suggest that the max pull-out capacity of anchor capacity to each the soil condition. Also, the MLT anchors can be used to achieve both structural enhancement and economic construction in earth retaining or supporting structures.

• Journal of the Korean Society of Safety
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• v.29 no.1
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• pp.25-30
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• 2014

This paper deals with a numerical study on the deformation of a mono tendon anchor head. The anchor head is used to introduce the compression to concrete, and consists of wedges and a head. All kinematics, material and contact nonlinearity are included in the precise analysis of a mono tendon anchor head. A numerical study on a mono tendon anchor head is performed to investigate effects of friction and eccentricity of load by ABAQUS. From the numerical results, it is verified that the deformation of a mono tendon anchor head is affected by characteristics of materials, boundary condition between wedge and anchor head, eccentricity of load, etc.

• Journal of the Korean Geotechnical Society
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• v.17 no.3
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• pp.59-68
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• 2001

풍화토 지반에 설치된 그라운드 앵커의 하중전이 현상을 규명하기 위하여 성균관대학교 지반시험장에서 인발시험을 수행하였다. 지반과 구조물을 일체화시키는데 사용하는 앵커는 앵커체와 지반의 마찰력에 의해서 구조물을 지지하는 역할을 하며 앵커의 하중과 변형의 관계를 규명하기 위해서는 앵커의 마찰력 분포의 변화(하중전이)가 중요한 요소가 된다. 하중 재하시 앵커체에 발생하는 하중전이 분포는 앵커의 인발 지지력과 밀접한 관계가 있고 앵커체의 종류(인장형 또는 압축형), 정착장의 길이, 지반 조건 등에 따라 분포 양상이 변하기 때문에 하중전이를 이해하기 위해서는 강선과 그라우트의 하중분포 그리고 앵커 그라우트체와 지반과의 마찰력 분포를 알아야 한다. 앵커의 자유장의 강선에 작용하는 응력, 그라우트체에 작용하는 응력, 그리고 정착장 강선의 응력을 계측하여 강선과 그라우트의 정착응력 및 그라우트와 지반에서의 마찰력 분포를 구함으로써 강선-그라우트-지반의 복합적인 거동에 따른 각 하중 단계마다의 하중전이 분포를 구하였다. 또한 현장시험 결과의 신뢰성 확보를 위하여 수치해석 모델링을 통하여 해석을 수행하여 비교하였다.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.994-1000
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• 2004

It is growing the application of the removal ground anchor with tension force for earth retaining constructions in the downtown. Nowadays, we can find the compression dispersion anchor on many site. But, it is occur some probelems in behabior of anchors because of impossible to tense p.c strand uniformly with existing equipment due to different length of p.c strand. So we tried to tense each p.c strand uniformly with auto back equipment in-situ test. This study compared and analyzed in-situ test results of an existing equipment with those of auto back equipment by appling elastic theory. As a result of the test, It has been proved that differences of tension force in the existing equipment increases with increasing the number of p.c strands. This can cause the ultimate failure of the concentrated p.c strand and the shear failure of ground. So it has been proved that auto back equipment is necessary.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.275-282
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• 1998

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.231-239
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• 2001

건설 현장에서 널리 사용되고 있는 그라운드 앵커의 거동 특성을 연구하기 위하여 계측기를 부착한 일곱 개의 그라운드 앵커를 국내에 널리 분포되어 있는 화강 풍화토 지반인 $\bigcirc$$\bigcirc$$\bigcirc$대학교 지반 시험장에 설치하여 인발 시험을 수행하였다. 저압 그라우트 인장형 앵커 3개와 압축형 앵커 4개를 시험하였고, 시험은 AASHTO 규정에 의거한 인발시험, 크리프시험, 장기거동시험을 수행하였다. 시험 결과로부터 화강 풍화토 지반에 설치된 저압그라우트 직선형 앵커의 지반과의 마찰계수, 크리프 변형율, 하중감소 특성을 평가하였다.

• Steel and Composite Structures
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• v.32 no.4
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• pp.497-507
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• 2019

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.