• Journal of Welding and Joining
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• 제5권3호
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• pp.28-37
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• 1987

To clarify the debonding phenomena of clad steel, the effect of thermal treatment (temperature, holding time) on the interfacial strength of clad steel was preliminarily investigated. From this study, it was confirmed that the interfacial strength of clad steel was deteriorated by thermal treatment and the amount of strength deteriorated, depending on the condition of thermal treatment, could be evaluated by the following equation. ${\sigma}_{ HT}/{\sigma}_{i}/=A_{0}-A\;exp(-Q/RT)log(t/t_{0})$ This equation implies that temperature has a far strong effect on strength deterioration than tiem. The deterioration of interfacial strength of clad steel after thermal treatment may be derived from the thermal stress caused by the difference in thermal expansion coefficient between component materials and microstructural change along the interface.

• 한국구조물진단유지관리공학회 논문집
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• 제4권2호
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• pp.151-158
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• 2000

A study on the strength of steel tubular column filled with concrete under cocentrically compressed load is presented in this paper. This paper is structured as follows. The first section briefly discusses the M-N relationship formula derived for CFT, highlighting the additional moment effect. Next, the simple superposed method used to generate the strength formula of CFT loaded concentrically is described. In the final portion of this paper, the presented formula is compared to experimental data reported. The applicability of CFT strength formula presented here is limited somewhat by scope of concrete strength but can predict the strength of CFT simply and rapidly. The objective of this paper is to approach the strength of CFT theoretically and to examine the feasibility of presented formula.

• Structural Engineering and Mechanics
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• 제73권4호
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• pp.437-445
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• 2020

The microstructure and mechanical properties of concrete will degrade significantly at high temperatures, thus affecting the bond strength between reinforcing steel and surrounding concrete in reinforced concrete members. In this study, the effect of individual and hybrid fiber on the local bond-slip behavior of lightweight aggregate concrete (LWAC) after exposure to elevated temperatures was experimentally investigated. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths of the pullout specimens were 4.2 times the bar diameter. The parameters investigated included concrete type (control group: ordinary LWAC; experimental group: fiber reinforced LWAC), concrete strength, fiber type, and targeted temperature. The test results showed that for medium-strength LWACs exposed to high temperatures, the use of only steel fibers did not significantly increase the residual bond strength. Moreover, the addition of individual and hybrid fiber had little effect on the residual bond strength of the high-strength LWAC after exposure to a temperature of 800℃.

• Computers and Concrete
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• 제11권5호
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• pp.463-473
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• 2013

As known, concrete classes are described as strength of standard specimens produced and kept in ideal conditions, not including reinforcement and not subjected to any load effect before. Under the circumstances, transforming core strengths to the standard specimen strength is necessary and considering all parameters, affected on the core strength, is inevitable. In fact, effects of the reinforcement and the load history on concrete strength are generally neglected when these mentioned transforms are performing. The main purpose of this paper is investigating the effects of the reinforcement and the load history on the core strength. This investigation is experimentally performed on cores drilled from specimens having different keeping conditions, reinforced, unreinforced, subjected to bending and central pressure in various proportions of failure load during specified periods. Obtained results show that the importance of these effects cannot be neglected.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.31-32
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• 2020

This study measured the mechanical performance and residual strength of high strength/normal strength mortar mixed with waste glass fine aggregate after alkali-silica reaction and alkali-silica reaction. As a result, the effect of improving the slip phenomenon of the waste glass fine aggregate in the high-strength mortar was not significant, but rather the amount of ASR was increased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.250-253
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• 2000

The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. Unidirectional FRP made by pultrusion method has comparatively lower compressive strength than tensile strength. Compressive strength of unidirectional FRP may be increased by filament winding layer which has tensile stress when compressive stress was loaded. In this study, compressive strength and stresses of FRP rods were simulated according to the winding orientation of glass fiber. Inner part of FRP was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method. Simulated value and real evaluated compressive strength were compared to investigate stresses which is prominent to the fracture of FRP. The shear stresses had a great effect on the strength of FRP although the stress of parallel direction of FRP was much higher.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.436-439
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• 2003

FRP has been used widely for insulator. FRP consists of fiber and resin. The fiber contributes the high strength and modulus to the composite. The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. In this study, FRP was made unidirectionally by pultrusion method. Outer part of the FRP was made by filament winding method to give fiber orientation to the FRP. And outer part of FRP was also made by wrapping method. The bending strength and bending stresses of FRP rods were simulated according to the winding orientation of glass fiber. The bending strength of FRP was also evaluated. The results of simulation and evaluation were compared each other to investigate main stresses which affect the fracture of FRP. The main stresses which had a great effect on the strength of FRP were shear stresses. Bending strength of the FRP was different with the winding angle. The bending strength of $15^{\circ}$ winded FRP was the highest.

• The Journal of Korean Physical Therapy
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• 제7권1호
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• pp.43-49
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• 1995

The purpose of this study were to determine the effect of testing posture and elbow position on grip strength. Two hundred college students 100 males and 100 females aged 18 to 28 years, participated in the study. A Grip-Strength Dynamometer was used to measure the grip strength in two testing posture(sitting and standin) and four elbow position$(0^{\circ},\;45^{\circ},\;90^{\circ}\;and\;135^{\circ}\;flexion)$ correlations and t-test was used to determine any significant difference in grip strength between the testing posture and the elbow position. The results were as follows : 1. The grip strength was affected by testing pasture and flexion degree of elbow. 2. The grip strength was stronger in the standing than sitting in subjects 3. The grip strength decreased according to elbow flexion increase in subjects. 4. The higher grip strength gained in the standing with the elbow 0 flexion. 5. The grip strength by elbow flexion degree showed significant difference at sitting and standing posture. The grip strength was significant differenced by testing position at same elbow flexion degree.

• 한국건축시공학회지
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• 제10권4호
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• pp.113-122
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• 2010

In this study, 150MPa ultra-high-strength concrete was manufactured, and its performance was reviewed. As technically meaningful autogenous shrinkage reportedly occurs at a W/B ratio of 40% or less, although it occurs in all concrete regardless of the W/B ratio, the effects of the use of expansive admixture and shrinkage reducer, or of the friction and restraint of forms that may result in the effective reduction of autogenous shrinkage, were reviewed. As a result, considering the flow and strength characteristics, it was found that the slump flow time was shorter with expansive admixture, and shortest with shrinkage reducer. All specimens with $30kg/m^3$ expansive admixture showed high strength at early material age. Their strength decreased due to the expansion cracks when there was excessive use of expansive admixture, and the use of shrinkage reducer did not influence the change in the strength according to the material age. The expansive admixture had a shrinkage reduction effect of 80%, while the shrinkage reducer had a shrinkage reduction effect of 30%, indicating that the expansive admixture had a stronger effect. It seems that mixing the two will have a synergistic effect. The shrinkage reduction rate was highest when the W/B ratio was 20%. The form suppressed the expansion and shrinkage at the early period, and the demolding time did not significantly influence the shrinkage. The results of the study showed that the excessive addition of expansive admixture leads to expansion cracks, and the expansive admixture and shrinkage reducer have the highest shrinkage reduction effect when they are mixed.

• 콘크리트학회논문집
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• 제24권5호
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• pp.525-533
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• 2012

이 연구에서는 UHPCC에서 섬유혼입률에 따른 초기균열강도 및 휨인장강도의 변화를 0~5 vol.% 범위에서 조사하였으며, 노치의 여부에 따른 영향을 파악하기 위해 노치가 없는 보에 대한 4점 재하실험 및 노치 낸 보에 대한 3점 재하실험을 같이 실시하였다. 실험 결과로부터 섬유혼입률이 증가함에 따라 휨인장강도는 선형적으로 강도가 향상됨을 확인할 수 있었고, 초기균열강도의 경우에는 1 vol.% 이상에서는 강도향상을 나타내었으나 그 이하의 섬유혼입에서는 강도향상 효과가 거의 없는 것으로 나타났다. 노치 유무에 따른 휨 실험으로부터 구한 UHPCC의 초기균열발생강도 및 휨 인장강도를 비교했을 때, 섬유혼입률에 따라 노치의 영향이 변하는 것으로 나타났다. 섬유혼입률이 증가함에 따라 노치에서의 응력집중의 영향이 감소하여 강도 차이가 점차 줄어들었으며, 높은 섬유혼입률에서는 노치에 의한 응력집중효과는 없어지고 균열면의 상태 및 크기효과의 영향이 지배적으로 작용하여 노치낸 보의 강도가 좀 더 크게 나타났다.