• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.213-226
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• 2000

지반 앵커(이하에서는 "앵커"로 칭한다)는 앵커두부, 자유부, 정착부로 나누어져 있다. 현재 주로 사용되고 있는 앵커는 지반과 앵커체 표면의 마찰저항력에 의해 지지하는 마찰방식이며, 앵커체에 발생하는 응력에 따라 크게 인장형과 압축형 앵커로 나누어진다. 그런데, 현재까지 이들 앵커의 설계 및 극한하중의 결정은 대부분이 인장형 앵커에 대한 것으로서, 긴장시 압축형 앵커의 선단정착부의 응력집중으로 이한 그라우트 압축저항에 대해서는 명확히 연구되어져 있지 않다. 본 연구에서는, 현장과 비슷한 조건에서 실내시험을 실시하여 선잔 장착부 그라우트의 보강형식에 따른 압축거동특성과 보강효과, 지반의 구속(정지와 포아송 구속)을 고려한 압축형 앵커의 선단 정착부 그라우트 압축저항력 산정식을 제안하였다.정식을 제안하였다.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.23-34
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• 1999

In designing PSC box girder bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code. In this study the creep and shrinkage test were carried out for four curing ages of concrete which was applied to the pretressed concrete box-girder bridge at a construction site, and the results of test were compared to the values of prediction by the design code. Shrinkage test shows that the test results are similar to KSCE-96 and JSCE-96 but very higher than other prediction model and creep test results are generally similar to ACI-209 and DSCE-96 but lower than other prediction models in contrast to shrinkage test.

• Structural Engineering and Mechanics
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• v.34 no.2
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• pp.189-211
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• 2010

The behaviour of a reinforced concrete tension member is governed by the contribution of concrete between cracks, tension stiffening effect. Under highly repeated loading, this contribution is progressively reduced and the member response approximates that given by the fully cracked member. When focusing on the unloaded state, experiments show deformations larger than those of the naked reinforcement. This has been referred to as negative tension stiffening and is due to the fact that concrete carries compressive stresses along the crack spacing, even thought the tie is subjected to an external tensile force. In this paper a cycle-dependent approach is presented to reproduce the behaviour of the axially loaded tension member, paying attention to the negative tension stiffening contribution. The interaction of cyclic bond degradation and time-dependent effects of concrete is investigated. Finally, some practical diagrams are given to account for the negative tension stiffening effect in reinforced concrete elements.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.589-595
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• 2011

Laminated glass fiber-reinforced plastic (GFRP) composites were applied to an insulating structure of a magnet system for a nuclear fusion device. Decreased inter-laminar strength by a strong repulsive force between coils which is induced a problem of structural integrity in laminated GFRPs. Therefore, it is important to investigate the inter-laminar characteristics of laminated GFRP composites in order to assure more reliable design and better structural integrity. Three types of the laminated GFRP composites using a high voltage insulating materials were fabricated according to each molding process. To evaluate the grade of the fabricated composites, mechanical tests, such as hardness, tensile and compressive tests,were carried out. The autoclave molding composites satisfied almost of the mechanical properties reguested at the G10 class standard, but the vacuum impregnation (VPI) and Prepreg composites did not.

• Steel and Composite Structures
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• v.42 no.4
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• pp.477-487
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• 2022

The shear stiffness of headed-stud shear connectors has no unified definition due to the nonlinear characteristics of its load-slip relationship. A unified framework was firstly adopted to develop a general expression of shear load-slip equation for headed-stud shear connectors varying in a large parameter range based on both force and energy balance. The pre- and post-yield shear stiffness were then determined through bilinear idealization of proposed shear load-slip equation. An updated and carefully selected push-out test database of 157 stud shear connectors, conducting on studs 13~30mm in diameter and on concretes 30~180 MPa in cubic compressive strength, was used for model regression and sensitivity analysis of shear stiffness. An empirical calculation model was also established for the stud shear stiffness. Compared with the previous models through statistical analysis, the proposed model demonstrates a better performance to predict the shear load-slip response and stiffness of the stud shear connectors.

• The Journal of Korea Robotics Society
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• v.17 no.4
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• pp.493-499
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• 2022

This paper presents the design for the kinematic structure of a system for an automatically moored 6000 ton autonomous ship in a port, and the process and results of optimal design for the link cross-sectional shape. We propose an automatic mooring system with a PPP type serial manipulator structure capable of linear motion in the XYZ axis. The mooring force applied by the mooring system was derived with dynamics simulation tool "ADAMS". The design goal is the minimization of the cross-sectional area of the link. Constrains include compressive stress and shear stress. The optimization problems were solved by using the sequential quadratic programing method implemented in the fmincon package. The shape of the cross section was assumed to be rectangle. Through future research, we plan to manufacture automatic mooring system for 6000ton class autonomous ship.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.1-12
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• 2022

Based on the extended spatial mobilization plane (SMP) criterion, we present an elastic-brittle-plastic solution for an axisymmetric cylindrical tunnel. The influences of the intermediate principal compressive stress and material strain-softening behavior are considered. Closed-form formulas for the critical support force, radius of plastic zone, and distributions of stress and displacement in surrounding rock are proposed. The elastic-plastic solution based on SMP is compared with the Kastner solution to verify the credibility of the obtained elastic-plastic solution. The elastic-brittle-plastic solution following the SMP criterion and the current solution based on the Mohr-Coulomb criterion are also compared. The rock strain-softening rate and the intermediate principal stress affect the stability of the surrounding rock. The results provide guidance for optimizing the design of support systems for tunnels.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.694-701
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• 2022

This paper introduces a study of concrete structures with a broken tire and a flat tire as a complete overhaul. The materials used to make concrete in this study are solid aggregate, cement, sand, flat tire, broken wheel, drinking water, and Ordinary Portland Cement. A total of 6 main compounds were thrown into solid cylinders and replaced by 0% as a controller followed by 5% and 10%. The cylinder pressure test of the concrete is done by applying the same pressure to the cylinders until a failure occurs. The results of the pressure test show that by applying 5% aggregation the pressure decreases. In Crumb wheel joints, the compression force decreases constantly as the percentage change increases. Therefore, the crumb wheel is not recommended for use as a complete replacement due to its compressive church power.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.594-605
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• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By investigating existing experiments and numerical results, it was found that flexural pinching which has no relation with shear action appears in RC members subject to axial compression force. However, members with specific arrangement and amount of re-bars, have the same energy dissipation capacity regardless of the magnitude of the axial force applied even though the shape of the cyclic curve varies due to the effect of the axial force. This indicates that concrete as a brittle material does not significantly contribute to the energy dissipation capacity though its effect on the behavior increases as the axial force increases, and that energy dissipation occurs primarily by re-bars. Therefore, the energy dissipation capacity of flexure-dominated member can be calculated by the analysis on the cross-section subject to pure bending, regardless of the actual compressive force applied. Based on the findings, a practical method and the related design equations for estimating energy dissipation capacity and damping modification factor was developed, and their validity was verified by the comparisons with existing experiments. The proposed method can be conveniently used in design practice because it accurately estimates energy dissipation capacity with general design parameters.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.519-533
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• 2023

In this study, the linear cutting tests of pick cutters were carried out on a granitic rock with the average compressive strength over 100 MPa. From the tests, the correlation between the cutter acting force and the temperature measured by infrared thermal imaging camera during rock cutting was analyzed. In every experimental condition, the maximum temperature was measured at the rock surface where the chipping occurred, and the temperature generated in the rock was closely correlated with the cutter acting force. On the other hand, the temperature of a pick cutter increased up to only 36℃ above the ambient temperature, and the correlation with the cutter force was not obvious. This can be attributed to the short cutting distance under laboratory conditions and the high thermal conductivity of the tungsten carbide inserts. However, the relatively high temperature of the tungsten carbide inserts was found to be maintained. Therefore, it is recommended that a reinforcement between the insert and the head of a pick cutter or the quality improvement of silvering brazing in the production of a cutter is necessary to maintain the high cutting performance of a pick cutter.