• Geomechanics and Engineering
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• 제20권6호
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• pp.497-503
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• 2020

In the Kingdom of Saudi Arabia, the shallower depth of the earth's crust is composed of loose dune or beach sand with soluble salts. The expansive behavior of salt bearing soil, fluctuation of ground water table and extreme environmental conditions offer a variety of geotechnical problems affecting safety and serviceability of the infrastructure built on it. Despite spending money, time and other resources on repair and rehabilitation, no significant attention is paid to explore the root causes of excessive differential settlement and cracking to these facilities. The scientific solution required to ensure safety and serviceability of the constructed infrastructure is to improve the strength and durability properties of the supporting ground. In this study, shredded plastic is employed as a low cost and locally available additive to improve strength characteristics of the desert sand. The study shows a remarkable increase in the shear strength and normal settlement of the soil. A seven (07) degree increase in angle of internal friction is achieved by adding 0.4 percent of the shredded plastic additive. The effect of different proportions and sizes of the plastic strips is also investigated to obtain optimum values. Such a long-lived solution will seek to reduce maintenance and repair costs of the infrastructure facilities laid on problematic soil along with reduction of environmental pollutants.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.193-197
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• 2008

Recently, it increases in use of CFT(Concrete filled steel tube, below CFT) that is an excellent internal force and deformation capacity because material and method are required to be diversification and High-Performance according to increase the super-high structure. And it is proposed to use high-strength Concrete Filled steel Tube Column. But it is difficult quantitative evaluation about fire-resist performance of CFT because steel tube bind concrete. Also, the case of high strength CFT is feared that spalling occur inside. Therefore, this study made CFT specimen that determine the factor(which is strength of concrete) and then CFT column was exposed to heating controlled as closely as possible the ISO-834 standard fire curve. Also, it tried to analyze internal temperature through nonlinear transient heat flow analysis.

• 한국농공학회논문집
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• 제50권5호
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• pp.39-50
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• 2008

This study are decided the mix proportion method of latex modified concrete for agricultural concrete structures from the results of workability and strength test with mix proportion factor. For mix proportion factor, this study are selected the water-cement ratio, unit cement amount and latex content. Also, this study were performed the slump, compressive strength test and microstructure analysis using the scanning electron microscope(SEM). The strength and slump of LMC are dependent with unit cement amount, latex content, and water-cement ratio. Especially, the strength of LMC are not controlled by single mix proportion factor but effected by combined mix proportion factor. Microstructure investigation are showed the LMC are reduced the internal pore volume and enhanced the transition zone between cement paste and aggregate interface. This effect get by consist of latex films in the concrete. Also, this study were recommended the mix proportion method for LMC. These mix proportions method are estimated the mix design for satisfied the target performance which are applied the agricultural concrete structure.

• 한국운동역학회지
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• 제31권1호
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• pp.64-71
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• 2021

Objective: This study investigated the different in isokinetic peak strength of the knee joint, and kinetics and kinematics in drop landing pattern of lower limb between the patellofemoral pain syndrome (PFPS) patients and normal. Method: 30 adult females were divided into the PFPS (age: 23.13±2.77 yrs; height: 160.97±3.79 cm, weight: 51.19±4.86 kg) and normal group (age: 22.80±2.54 yrs, height: 164.40±5.77 cm, weight: 56.14±8.16 kg), with 15 subjects in each group. To examine the knee isokinetic peak strength, kinematics and kinetics in peak vertical ground reaction force during drop landing. Results: The knee peak torque (Nm) and relative strength (%) were significantly weaker PFPS group than normal group. In addition, PFPS group had significantly greater hip flexion angle (°) than normal group. Moreover, normal group had significantly greater moment of hip abduction, hip internal rotation, and left ankle eversion than PFPS group, and PFPS group had significantly greater moment of knee internal rotation. Finally, there was significant differences between the groups at anteroposterior center of pressure. Conclusion: The PFPS patients had weakened knee strength, and which can result in an unstable landing pattern and cause of more stress in the knee joints despite to effort of reduce vertical ground reaction force.

• Geomechanics and Engineering
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• 제20권4호
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• pp.299-312
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• 2020

The aim of this paper was to investigating the effects of soil relative density, construction materials roughness, oil type (gasoil, crude oil, and used motor oil), and oil content on the internal and interface shear behavior of sand with different construction materials by means of a modified large direct shear test apparatus. Tests conducted on the soil-soil (S-S), soil-rough concrete (S-RC), soil-smooth concrete (S-SC), and soil-steel (S-ST) interfaces and results showed that the shear strength of S-S interface is always higher than the soil-material interfaces. Internal and interface friction angles of sand beds increased by increase in relative density and decreased by increasing oil content. The oil properties (especially viscosity) played a major role in interface friction behavior. Despite the friction angles of contaminated sands with viscous fluids drastically decreased, it compensated by the apparent cohesion and adhesion developed between the soil grains and construction materials.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.155-156
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• 2018

In this study, surface spalling and explosive spalling of ring-type ultra-high strength concrete under rapid heating and slow heating were investigated. In rapid heating, the internal temperature difference of the concrete is large, so that continuous surface spalling occurs. However, in slow heating, the difference in the internal temperature of the concrete is small, resulting in explosive spalling at a time. Since the heating condition has a great influence on the internal temperature of the concrete, it is necessary to consider the spalling of the concrete under various heating conditions.

• 한국지반환경공학회 논문집
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• 제11권3호
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• pp.23-32
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• 2010

흙채움 마대는 현장의 재료를 사용하여 간편하게 사면 및 제방의 복구나 보강에 사용되고 있다. 이런 흙채움 마대의 전단저항력을 증가시키기 위해 흙채움 마대 상 하면에 벨크로(Velcro)를 부착한 흙채움 마대가 개발되었으며, 벨크로를 부착한 흙채움 마대의 역학적 특성을 분석하기 위해 대형직접전단실험과 원호파괴를 가정한 실내모형실험이 수행되었다. 실제 벨크로가 부착된 마대를 이용해 사면을 설계하기 위해 흙-토목섬유 요소실험을 실시하여 강도정수를 파악하였다. 그리고 사면형성 시 벨크로와 흙채움 마대가 혼재하고 있기 때문에 정확한 파괴면을 알 수 없다. 따라서 실내모형실험을 통해 내적파괴에 대한 거동을 분석하고, 역해석을 통해 설계강도정수를 제안하였다. 흙-토목섬유의 요소실험결과, 벨크로의 부착으로 인해 흙채움 마대 상호간의 전단저항 정수인 내부마찰각과 점착력의 증가가 나타났으며, 특히 내부마찰각보다는 점착력의 뚜렷한 증가가 나타난 것으로 분석되었다. 또한, 실내모형실험 결과, 지지력이 20%이상 증가해 대형장비의 주행성 증가와 시공속도의 증대를 가져올 것으로 판단된다.

• 농업생명과학연구
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• 제46권2호
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• pp.43-48
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• 2012

거대억새 자원의 활용도 제고방안의 일환으로 거대억새 파티클을 이용하여 보드를 제조하고 수지첨가량, 수지타입 및 밀도에 따른 물성을 검토하였다. 흡수율은 보드의 밀도 및 수지첨가량이 증가할수록 감소하였으며, 휨강도와 박리강도는 밀도 및 수지 첨가량이 증가할수록 파티클간 결합력이 강해져 증가하였다. 두께 팽창률은 보드의 밀도가 증가함에 따라 증가하였고 수지 첨가량이 많을수록 감소하였다. 수지타입에 따라 두께 팽창률과 흡수율은 액상 페놀수지로 제조한 보드가 더 나은 치수안정성을 보였고, 보드밀도 $0.4g/cm^3$ 로 제조한 경우 수지 첨가율 11~13% 일 때 휨강도는 분말상 및 액상 페놀수지 간에 차이가 없었으며, 박리강도는 액상의 페놀수지로 제조한 보드가 더 좋은 값을 나타내었다.

• Clinics in Shoulder and Elbow
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• 제13권1호
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• pp.53-57
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• 2010

목적: 1, 2단계 충돌 증후군과 회전근 개 파열이 있는 환자 사이의 근력 결핍 차이를 비교하였다. 대상 및 방법: 43명의 1, 2단계 충돌 증후군 환자 군 (1군)과 21명의 회전근 개 파열 환자 군 (2군)을 대상으로 하였다. 외회전, 내회전, 외전과 내전의 근력을 $60^{\circ}/sec$ 등속성 검사로 평가했다. 몸무게로 보정한 양측의 최대 우력, 총 일의 양, 평균 근력과 동측의 주동근과 길항근의 비율을 측정하였다. 결과: 양 군에서 몸무게로 보정한 최대 우력의 결핍은 외전에서 각각 $28.48{\pm}23.76%$ (1군), $29.12{\pm}32.81%$ (2군) (p=0.929), 내전에서 $7.20{\pm}13.98%$, $18.94{\pm}19.52%$ (p=0.021), 외회전에서 $16.88{\pm}13.76%$, $25.80{\pm}24.07%$ (p=0.221), 내회전에서 $14.15{\pm}25.67%$, $29.02{\pm}35.06%$ (p=0.059)로 측정되었다. 평균 근력과 총 일의 양에서 2군은 1군과 비교하여 내전력과 내회전력의 결핍이 유의하게 증가되었다. 결론: 2군에서 1군보다 더 큰 근력 결핍을 보였다. 1, 2단계 충돌 증후군 에서 3단계로 진행 시내회전과 내전 근력 결핍 변화가 더 크게 나타날 가능성이 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.357-364
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• 1997

In this experiment high-strength concrete of good workability is made by means of either replacing unit cement quantity to fly-ash by 20% or using low heat cement to reduce the internal hydration heat suggested as the fault of concrete. Concrete is poured through ready mixed concrete to test the ability of applying to the substantial works and is carried out the test of flowing and core strength and record of temperature of imitating specimens. It is capable to apply high-strength concrete replaced to fly-adh 20% to the substantial works through the experiment