• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.260-265
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• 1994

High strength concrete(65MPa) was used for construction of the bulk cement storage silo by using sliding form. This paper presents mix design, production, quality control and experience with field application of high strength concrete under cold weather conditions. It is shown to be possible to produce high strength concrete of compressive strength of 50~60 MPa by using high-range water reducer to lower w/c ratio with appropriate quality control.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.322-327
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• 1997

This paper investigates the effects of shot peening on mechanical properties of SAE 9254, which is a spring steel used for the suspension system of automobiles. Rotary Bending Fatigue test is accomplished and the results are summarized as fellows : 1. The tensile strength and the hardness do not change so much. 2. The layer of highly residual stress is obtained by multi-stage shot peening. 3. The fatigue strength seems to be improved by residual stress. 4. The fatigue strength of un-peened and multistage shot peened material are 425 MPa and 756 MPa, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.423-428
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• 1994

High strength concrete was placed at the mass concrete slabs, walls, pillars of RC building from August till August. And the construction is going on now. This paper presents mix design, production, quality control and experience with field application of high strength ready-mixed concrete under hot weathered conditions. It is shown to be possible to produce high strength concrete that has 45MPa compressive strength using superplasticizer and cement replaced with 20% fly-ash with appropriate control.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.494-497
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• 2004

This paper presents the analysis results predicted by the upper bound approach in the limit analysis of concrete incorporating the original plastic and crack sliding solutions for short high-strength concrete beams that varied the compressive strength of concrete, and the shear span-to-depth and vertical shear reinforcement ratios. The significance of the distance away from the support to define the location where the yield line starts and the properties of cracked concrete, particularly related to high-strength concrete, is identified.

• Journal of Korean Society for Quality Management
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• v.24 no.3
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• pp.19-30
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• 1996

We treat problems of estimating reliability R(t) = P[Y(t) ＞ X(t)] in the time dependent strength-stress model in which a unit of stress X(t) is subjected to environmental strength Y(t) at time t. In this paper we introduce a special model of R(t) with fixed strength and unaccumulated stress case, and propose a Mann-Whitney-Wilcoxon type estimator of R(t).

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.290-292
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• 2004

In this paper, static and fatigue load tests for the specimens, components and carbody were carried out to investigate the strength of welded joints in aluminum rolling stock. Tensile load test results showed that the static strength of welded joint for heat-treated alloys is reduced significantly and fatigue strengths are scattered by the welding imperfections. Component and whole carbody fatigue test results showed agreements with the design fatigue strength standards for specimens of same joint detail. Test results revealed that full penetration welding and strict management of welding procedure are crucial for securing strength of welded joint in aluminum carbody.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.751-756
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• 2003

This Paper concerns the compressive strength development tendencies of concrete according to their Ages and curing conditions. The test results are on follows; (1) The compressive strength development of concrete appears larger according to the curing conditions under water curing, condition structural curing and field curing conditions. (2) The compressive strength development rate of concrete after 28 days' curing becomes smaller, but the case of lower strength of concrete not.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.803-808
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• 1998

As carbon fiber is a light-weight materials, high tensile strength and durability compared with rebar, the retrofitting method for RC structures using carbon fiber sheet (CFS) must be use widely. In this paper, the tensile strength test for carbon fiber sheet variable of CF's weight and elastic modulus to evaluate the design tensile strength of carbon fiber sheet which is needed for the strengthening design of CFS and the calculation of strengthening effect. As a result, the design tensile strength of CFS can be calculate using the effect coefficient of strengthening(α) of CFS, the average tensile strength of CFS and the standard deviation of CFS(equation 5)

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.140-145
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• 1991

Tests were conducted to get a mix proportioning of high strength concrete between σ28 and (C/W) using low quality materials easily purchased in situ. Superplasticizer was used as a chemical admixture to compensate low slump of base concrete keeping it up about 15±2㎝. General material properties such as modulus of elasticity, poisson's ratio, unit weight and stress-strain characteristic of high strength concrete were obtained. Test results show that mix proportioning of high strength concrete proposed in this paper have reasonable validity and these can be used as a design criteria in high strength concrete construction.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.53-58
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• 1996

This paper deals with the bending fatigue strength of sintering spur gears. The test specimens are used to sintering spur gear to be consisted of Fe-C-Ni-Mn and SCM415 spur gear. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and the enhancement of fatigue strength due to carburized treatment is clarified, Accordingly, this study presents the fatigue strength of sintering spur gear, SCM415 spur gear and carburized gears of them. The strength enhancement due to the carburized treatment is discussed.