• 대한통합의학회지
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• 제10권2호
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• pp.115-123
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• 2022

Purpose : The hamstring is a group of three muscles, biceps femoris, semitendinosus, and semimembranosus, placed behind the thigh. The hamstring is one of the most commonly injured muscles and usually occurs during high-speed, high-intensity exercise. The purpose of this study was to investigate the effect of static stretching and eccentric exercise of hamstrings on flexibility, strength, and functional performance. Methods : This study was conducted on 28 healthy adults. Subjects were divided into a static stretching group (n=15) and an eccentric exercise group (n=13). Subjects measured hamstring flexibility (active knee extension test), hamstring strength (concentric and eccentric peak torque), and functional performance (triple hop for distance and modified 20 m sprint). The intervention was conducted three times a week for six weeks. To compare the difference between values before and after the intervention, paired t-test was used, and an independent t-test was used to compare between groups. Results : In both groups, the active knee extension test, concentric peak torque, triple hop test, and 20 m sprint significantly increased after the intervention compared to before the intervention (p<.05). However, no significant difference was found in eccentric peak torque after intervention in both groups (p>.05). No significant difference was found between the two groups in the effect on the variables (p>.05). Conclusion : Both interventions were found to be effective for flexibility, concentric strength, and functional performance. Eccentric exercise and static stretching are recommended to improve the flexibility and functional performance of the hamstring. This study's results will be considered essential data on the effectiveness of static stretching and eccentric exercise.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.467-470
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• 2005

This study was performed to evaluate the static strength of long-span PSC deck slabs. In the previous study, the minimum thickness of PSC deck slabs in the composite two-girder bridge was proposed. To examine the structural behavior and safety of the PSC deck slabs designed in accordance with the proposed minimum thickness, 1/3 scaled PSC deck slabs in the composite two-girder bridge were tested under the static loading. The test results were compared with the predicted values proposed by the code and Matsui. Test results showed ultimate static strength of the PSC deck slabs designed in accordance with the proposed minimum thickness have enough margin of safety. The static failure mode of each test specimen was punching shear mode.

• 터널과지하공간
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• 제13권3호
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• pp.180-186
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• 2003

동적 인장강도를 평가하기 위해 수치해석기법을 이용하여 홉킨슨효과를 가정한 동적 인장시험의 암석 파쇄 과정을 해석하였다. 동적 인장 파쇄 과정과 정적 인장 파쇄 과정에 명확한 차이가 있음을 밝혔으며, 동적 인장강도와 정적 인장강도의 상위는 응력집중현상과 응력재분배에 의해 발생된다는 것을 지적하였다. 그러나 정적파쇄와 동적파쇄 과정에 큰 차이가 있음에도 불구하고 정적 인장강도와 동적 인장강도는 미시적 인장강도의 균질성 계수가 증가함에 따라 미시적 인장강도의 평균치에 근접하였다. 본 연구로부터 암석의 불균질성은 동적 인장강도에 영향을 미치는 요인이며, 동적 인장강도와 정적 인장강도의 상위를 발생시키는 중요한 요인임을 지적하였다.

• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.388-395
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• 2016

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS. The group $IT4_S$ had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups $IT4_N$ and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

• 한국지반환경공학회 논문집
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• 제10권3호
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• pp.5-12
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• 2009

본 연구는 발전소의 적치장에서 채취한 석탄회의 정적 및 동적 강도를 제시하였다. 석탄회는 주로 저회로 이루어져 있으며 정적 및 동적 강도를 평가하기 위하여 NGI형 단순전단시험, 반복단순전단시험 및 직접전단시험을 수행하였으며, 이러한 시험으로부터의 강도를 모래의 강도와 비교하였다. 본 연구에 사용된 석탄회 속에 있는 저회는 입도분포에 의하면 모래로 분류되었으며 모래보다 높은 강도 특성을 보였다. 석탄회를 토목공사에 활용되기 위해서 사질토와 석탄회를 50:50의 비율로 배치플랜트에서 섞어 사용하는 것은 사질토층과 석탄회층을 교대로 층별 시공하는 것보다 비효율적이다. 혼합시공과 층별시공을 모사하기 위하여 모래와 석탄회가 50:50으로 조성된 시료를 준비하였다. 시험결과 혼합에 의한 시료가 층별시료보다 약간 큰 정적 및 동적 강도를 나타내었다. 높은 강도는 주로 저회의 모난 입자로부터 기인된 것으로 보인다. 혼합시료에서 액상화시의 반복응력비는 반복횟수가 증가함에 따라 층별시료보다 급격히 감소하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2001년도 제16회 학술발표회 논문초록집
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• pp.104-107
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• 2001

The purpose of this work is to investigate the static strength, the stress distribution, and the failure process of quasi-isotropic composite laminates made of two different matrices when loading directions are changed. We carried out static tests of $[0/-60/+60]_s$ and $[+30/-30/90]_s$ laminates. Two types of matrices used are AS4/epoxy and AS4/PEEK. The damage mechanisms of the quasi-isotropic laminate, $[0/-60/+60]_s$, strongly depend on the load direction applied to the laminate.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.145-150
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• 2002

Tubular joints having a large diameter in the offshore structure are reinforced using internal ring stiffener in order to increase the load carrying capacity. In this study, the static strengths of internally ring-stiffened tubular T-joints subjected to compressive brace loading are assessed. Nonlinear finite element analyses are used to compute the behavior of unstiffened and ring-stiffened T-joints. From the numerical results, internal ring stiffener is found to efficient in improving the ultimate capacity, and reinforcement effect are calculated. The influence of geometric parameters for members and ring is evaluated. Based on the FE results, regression analysis is performed considering practical sizes of ring stiffener, finally strength estimation formulae for ring-stiffened T-joints are proposed.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.130-138
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• 2004

In this paper, the structural strength of a rolling stock seat were numerically evaluated under several design load conditions based on the UIC requirements. The rot]ins stock seat was designed for the high speed train of a Chinese conventional line. To maximize its weight reduction and structural strength, an aluminium alloy, ALDC8-T5, was applied to the base frame, side frames and armrests. The designed seat frame satisfied the strength requirements on inertia loads and fatigue test conditions. However, it couldn't satisfy the requirements on the static test conditions of UIC 566 OR. Therefore, some design modifications were suggested and numerically evaluated whether the static test requirements could be satisfied or not.

• 한국철도학회논문집
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• 제7권1호
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• pp.32-36
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• 2004

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Static load test has been performed up to date to assess structural safety of the carbody. However, static load test is not sufficient to evaluate fatigue strength of the carbody, because fatigue failure is caused by dynamic load. In this study, the established load test methods for carbody are described and the characteristics of the methods are discussed. Also, a testing method to simulate dynamic loading condition is proposed for evaluation of fatigue strength of the carbody. The results by the proposed testing method are compared with the results by the static load test and new findings are discussed.

• Steel and Composite Structures
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• 제25권5호
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• pp.617-624
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• 2017

In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity ($M_u$) and moment demand ($M_d$) to plastic moment capacity ($M_p$) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min $[(M_u-M_d)/M_p]$ of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.