• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.315-320
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• 1998

The experimental set-up and one-dimensional analytical model have been developed to investigate the tensile behavior of reinforced concrete member due to restrained drying shrinkage. The experimental results have been compared with the analytical prediction of the maximum residual stress of steel and concrete due to restrained shrinkage. The tensile residual stress concrete by one-dimensional bilinear model shows 0.19 and 0.63 of tensile strength for 0.83% and 3.29 of steel ratio. The residual tensile stress of concrete increases as the steel ratio increases. The effect of steel fiber has not influenced the residual stress due to restrained shrinkage of concrete.

• Advances in concrete construction
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• 제3권4호
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• pp.283-293
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• 2015

This paper presents the effects of elevated temperatures of $400^{\circ}C$ and $800^{\circ}C$ on the residual compressive strength and failure behaviour of fibre reinforced concretes and comparison is made with that of unreinforced control concrete. Two types of short fibres are used in this study e.g., steel and basalt fibres. The results show that the residual compressive strength capacity of steel fibre reinforced concrete is higher than unreinforced concrete at both elevated temperatures. The basalt fibre reinforced concrete, on the other hand, showed lower strength retention capacity than the control unreinforced concrete. However, the use of hybrid steel-basalt fibre reinforcement recovered the deficiency of basalt fibre reinforced concrete, but still slightly lower than the control and steel fibres reinforced concretes. The use of fibres reduces the spalling and explosive failure of steel, basalt and hybrid steel-basalt fibres reinforced concretes oppose to spalling in deeper regions of ordinary control concrete after exposure to above elevated temperatures. Microscopic observation of steel and basalt fibres surfaces after exposure to above elevated temperatures shows peeling of thin layer from steel surface at $800^{\circ}C$, whereas in the case of basalt fibre formation of Plagioclase mineral crystals on the surface are observed at elevated temperatures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.549-552
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• 2006

Generally the ultra-high strength steel reinforced concrete has rich mix composition composed of high-strength type mineral admixtures and as a result of very low water-binder ratio(about under w/b=25%), it reveals ultra-high compressive strength(about over 100Mpa). Also, in order to obtain sufficient toughness after construction, we usually mix a large quantity steel fiber with ultra-high strength steel reinforced concrete therefore we must use proper mixer for workability. When we make the ultra-high strength steel reinforced concrete we need more long mixing time or much super-plasticizer than when we manufacture normal concrete. These bring about economical problems and performance deterioration. Therefore, in this study, in order to manufacture easily ultra-high strength steel reinforced concrete we develope a dedicated mixer for ultra-high strength steel reinforced concrete with high speed type. It carried out the examination for comparison between the dedicated and general type mixer, the analysis and counterplan of the point at issue when we manufacture ultra-high strength steel reinforced concrete by the dedicated mixer.

• Steel and Composite Structures
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• 제26권6호
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• pp.705-717
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• 2018

This paper presents a numerical investigation on the mechanical performance of concrete-filled dual steel tubular columns of circular section subjected to concentric axial load. A three-dimensional numerical model is developed and validated against a series of experimental tests. A good agreement is obtained between the experimental and numerical results, both in the peak load value and in the ascending and descending branches of the load-displacement curves. By means of the numerical model, a parametric study is carried out to investigate the influence of the main parameters that determine the axial capacity of double-tube columns, such as the member slenderness, inner and outer steel tube thicknesses and the concrete grade - of both the outer concrete ring and inner core -, including ultra-high strength concrete. A total number of 163 numerical simulations are carried out, by combining the different parameters. Specific indexes are defined (Strength Index, Concrete-Steel Contribution Ratio, Inner Concrete Contribution Ratio) to help rating the relative mechanical performance of dual steel tubular columns as compared to conventional concrete-filled steel tubular columns, and practical design recommendations are subsequently given.

• Advances in concrete construction
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• 제5권4호
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• pp.391-405
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• 2017

Cement acts as the most important component of concrete as it binds and holds the concrete together. But it is one of the major $CO_2$ emitters all over the world, during manufacturing (900 kg of $CO_2$ per 1000 kg). Some of the modern construction methods aim at reducing the amount of usage of cement and came out with numerous solutions for replacement of the same. One such supplement in current trend is the Steel dust or the Electric Arc Furnace Dust (EAFD), which is a waste product from the electric arc furnace when the scrap metal is melted. When the concrete containing steel dust is exposed to atmosphere, the environmental oxygen and moisture play role to form rust and ultimately the member becomes harder. As Cement is the binder of conventional concrete, only certain percentage of the same could be replaced by the new material, steel dust. Tests were conducted for the 28 days cube strength of M45 grade (suitable for prestressing) concrete which has 0%, 10%, 20%, 30%, 40% and 50% steel dust instead cement. From the test, the optimum percentage replacement of steel dust was obtained, for which the beams and overhead poles were cast, prestressed and tested for the failure load and deflections. A conventional concrete beam and overhead pole were also cast, prestressed and tested to compare the results with those of the beam and pole that contained steel dust. The load vs. deflection plot and other results from the test is also discussed.

• 산업기술연구
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• 제26권B호
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• pp.111-118
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• 2006

The reinforced concrete structure is one of the most popular structures in real construction. Concrete has been strengtened rapidly due to the development of new material and construction technology. But as the concrete has been getting stronger, the brittleness of material has increased and the better ductility has been required. So, the study for strengthening stiffener has been urgently needed. As we said above, it is expected that the use of high strength steel and concrete will be increased. However, The experimental data is not enough for solving problems of the use of high strengthened steel and concrete. In this research, we analyzed 45 combinations of the strength levels of concrete, the thickness of material and the steel strength with regard to simple Reinforced Concrete SLAB Beam bridge. The program MIDAS CIVIL was used to find the optimal combination. As a result, it was found that strength ratio per unit section is in inverse proportion to the strength of material and that the strengths of steel are respectively 400 MPa for low strengthened concrete and 300 MPa for high strengthened concrete. For economic aspect and usability, the effect of high strength steel is not as high as we expected it would be.

• Steel and Composite Structures
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• 제10권6호
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• pp.517-539
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• 2010

This paper presents the axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel and carbon steel hollow sections. The finite element method developed via ABAQUS/Standard solver was used to carry out the simulations. The accuracy of the FE modelling and the proposed confined concrete stress-strain model were verified against experimental results. A parametric study on stub concrete-filled columns with various elliptical hollow sections made with stainless steel and carbon steel was conducted. The comparisons and analyses presented in this paper outline the effect of hollow sectional configurations to the axial compressive behaviour of elliptical concrete-filled steel tubular columns, especially the merits of using stainless steel hollow sections is highlighted.

• 한국공간구조학회논문집
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• 제8권5호
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• pp.59-65
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• 2008

최근, 교량교각과 같은 기둥구조물의 사용성능을 향상시킴과 동시에 복잡한 도심지 내 효율적 공간활용을 위해 콘크리트 충전강관(CFT: concrete-filled steel tube)의 적용이 점차 증가하고 있다. 이러한 기둥구조물의 정확한 설계를 위해서는 재료 및 기하학적 특성에 따른 콘크리트 충전강관 기둥의 거동에 관한 실험적 연구가 요구된다. 이에 본 연구에서는 압축강도실험을 통하여 외경-두께비 (D/t) 및 강재-콘크리트 단면적비 (As/Ac)에 따른 콘크리트 충전강관 기둥의 극한강도 분포특성에 대해 명확히 파악하였다. 또한 콘크리트 배합강도에 따른 콘크리트 충전강관 기둥의 극한강도 분포특성을 실험을 통하여 명확히 파악하였다. 실험결과의 고찰을 통하여 압축하중을 받는 콘크리트 충전강관 기둥의 극한강도는 콘크리트 강도보다 강과의 단면특성에 주로 의존함을 알 수 있었다.

• 콘크리트학회논문집
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• 제11권4호
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• pp.137-145
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• 1999

The use of steel fiber reinforced to improve the strength and flexural toughness of concrete is well known, but reinforcement of polymer concrete with steel fibers has been hardly reported till now. Polymer concrete has high strength, durability and freeze-thaw resistance than that of cement concrete, but it has disadvantage such as low flexural toughness. In this paper, the strength characteristics and flexural toughness of steel fiber reinforced polymer concrete are investigated experimentally with various steel fiber aspect ratios($\ell$/d), and contents(vol.%). As the result, the flexural and splitting tensile strengths and flexural toughness were increased aspect ratio, and reach the maximums at a aspect ratio of 50. The relationship between the compressive, flexural and splitting tensile strength were high. And the relationship between flexural strength and strain energy was approximately linear.

• Architectural research
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• 제7권1호
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• pp.27-38
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• 2005

No specific guidelines are available for computing the bearing strength of connection between steel coupling beam and reinforced concrete shear wall in a hybrid wall system. There were carried out analytical and experimental studies on connection between steel coupling beam and concrete shear wall in a hybrid wall system. The bearing stress at failure in the concrete below the embedded steel coupling beam section is related to the concrete compressive strength and the ratio of the width of the embedded steel coupling beam section to the thickness of the shear walls. Experiments were carried out to determine the factors influencing the bearing strength of the connection between steel coupling beam and reinforced concrete shear wall. The test variables included the reinforcement details that confer a ductile behavior in connection between steel coupling beam and shear wall, i.e., the auxiliary stud bolts attached to the steel beam flanges and the transverse ties at the top and the bottom steel beam flanges. In addition, additional test were conducted to verify the strength equations of the connection between steel coupling beam and reinforced concrete shear wall. The proposed equations in this study were in good agreement with both our test results and other test data from the literature.