• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.365-370
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• 2001

The repairing technique of surface wrapping concrete structural members using fiber composite sheet have been widely used. The research efforts have been limited to studying relative strength increase of repaired concrete structures rather than ductility improvement based on composite material effect and the interface effect between composite and concrete. The compression tests of CFS(carbon fiber sheet) reinforced concrete specimens with various cross-sectional shapes and laminate angles have been peformed. FEM algorithm considering various parameters will be performed based on the obtained data. The results will be discussed in detail.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.923-928
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• 2002

Experimental and analytical study were conducted to develop the confined model of reinforced high strength concrete tied columns subjected to monotonically increasing concentric axial compression. Twenty-one large-scale columns(260$\times$260$\times$1200mm) used high strength concrete of 50 and 85MPa were fabricated to simulate an actual structural members size. Test results indicated that gains of strength and ductility of high strength concrete columns could be increased, if efficient arrangements and volumetric ratios of transverse reinforcements were provided. The proposed model satisfactorily predicted the experimental stress-strain curves for high strength concrete up to 100MPa.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.5
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• pp.603-608
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• 2010

In this study, one type of circular shaped composite tube was used, combined with reinforcing foam and without foam. Furthermore, CFRP(Carbon Fiber Reinforced Plastic) circular member manufactured from CFRP prepreg sheet for lightweight design. CFRP is an anisotropic material which is the most widely adapted lightweight structural member. The crashworthy behavior of circular composite material tubes subjected to static axial compression under same conditions is reported in this paper. Test was executed in order to compare the results to the energy absorption and collapse shape. The collapse mode during the failure process were observed and analyzed. The behavior of polymeric foams to the tubes crashworthiness were also investigated. According to the experimental results, specimens filled with foam are higher total energy absorption than the other specimens not filled with the foam.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.192-199
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• 2000

The spot-welded automotive side member which has a hat-shaped section and a double hat shaped section has been tested on the axial static(10mm/min) and quasi-static(50mm/min) compressing load. The collapse characteristics of automotive sections have been reviews on shift on shape and in width of the spot-voiding on the flange. On the basis of the results of tests and reviews, the optimum energy absorption capacity of the structure has been studied.

• Structural Engineering and Mechanics
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• v.51 no.6
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• pp.1017-1036
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• 2014

Steel tubes have an efficient shape with large second moment of inertia relative to their light weight. One of the main problems of these members is their low buckling resistance caused from having thin walls. In this study, steel foams with high strength over weight ratio is used to fill the steel tube to beneficially modify the response of steel tubes. The linear eigenvalue and plastic collapse FE analysis is done on steel foam filled tube under pure compression and three point bending simulation. It is shown that steel foam improves the maximum strength and the ability of energy absorption of the steel tubes significantly. Different configurations with different volume of steel foam and composite behavior is investigated. It is demonstrated that there are some optimum configurations with more efficient behavior. If composite action between steel foam and steel increases, the strength of the element will improve, in a way that, the failure mode change from local buckling to yielding.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.841-856
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• 1998

During the 1995 Hyogoken-Nanbu Earthquake, a reinforced concrete building, called Jeunesse Rokko, suffered intermediate damage by forming a beam-yielding (weak-beam strong-column) mechanism, which has been regarded as the most desirable earthquake resisting mechanism throughout the world. High cost to repair damage at many beam ends and poor appearance expected after the repair work made the owner decide to tear down the building. Nonlinear earthquake response analyses were conducted to simulate the behavior of the building during the earthquake. The influence of non-structural members was considered in the analysis. The calculated results were compared with the observed damage, especially the location of yield hinges and compression failure of spandrel beams, and the degree of cracking in columns and in column-girder connections.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.639-650
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• 2007

Applying the method calculating creep of Concrete Filled steel Tube (CFT) members based on the Elastic Continuation and Plastic Flow theory for concrete creep with the finite element method, the paper develops a new numerical method for the creep of CFT arch bridges considering effects of bending moment. It is shown that the method is feasible and reasonable through comparing the predicted stresses and deflection caused by the creep with the results obtained by the method of Gu et al. (2001) based on ACI209R model and experimental data of an actual CFT arch bridge. Furthermore, nine CFT arch bridges with different types are calculated and analyzed with and without the effects of bending moment. As a result, the bending moment has considerable influences on long-term deformations and internal forces of CFT arch bridges, especially when the section of arch rib is subjected to a large bending moment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.914-921
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• 2006

To describe the effect of the numerous and various oriented microcracks on the compressive and tensile concrete behaviors, the directional nonlocality is defined. The plasticity model using multiple failure criteria is developed for RC planar members in tension-compression. The crack damages are defined in the pre-determined reference orientations, and then the total crack damage is calculated by integrating multi-oriented crack damages. To describe the effect of directional nonlocality on the anisotropic tensile damage, based on the existing test results, the nonlocal damage factor is defined in each reference orientation. The reduced compressive strength in the cracked concrete is defined by the multi-oriented crack damages defined as excluding the tensile normal plastic strain from the compressive equivalent plastic strain. The proposed model is implemented to finite element analysis, and it is verified by comparisons with various existing panel test results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.219-226
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• 2003

보 유사법을 이용하여 연속 압축재의 유효길이 계수를 각 경간별로 결정하는 방법을 제안한다. 제안하는 보 유사법은 4가지 단계로 요약할수 있는데 그 첫 단계는 주어진 압축재를 이것과 동일한 단면성능 및 경간을 갖는 연속보로 치환하는 것이다. 제 2단계에서는 연속보 각 경간의 중앙에 가상 집중 횡하중을 작용시킨 후 이로 인한 지점들에서의 재단 moment를 계산한다. 이때 각 경간중앙의 가상 집중 횡하중 방향은 좌굴 mode를 고려하여 교호로 바뀌도록 한다. 제 3단계에서는 또 하나의 제안식과 재단 모멘트를 이용하여 Kinney의 부분 고정도를 결정한다. 최종단계에서는 부분 고정도를 이용하여 유효길이를 각 경간별로 산정 한다. 제안한 방법은 다 경간 압축재에서 어느 경간이 맨 먼저 좌굴을 일으키는지 또한 이때의 임계하중은 어떤 값을 갖는지를 예측하게 한다.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.195-201
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• 2000

The fundamental spot welded sections of automobiles (hat-shaped and double hat-shaped sections) absorb most of the energy in a front impact collision. The sections of various thickness, shape and weld width on the flange lave been tested on axial impact crush load (Mass 40kg, Velocity 7.19m/sec) using a vertical air pressure crash est device Characteristics of impact collapse have been reviewed and a structure of optimal energy absorbing capacity is suggested.