• 대한토목학회논문집
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• 제29권4A호
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• pp.307-313
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• 2009

본 연구에서는 철도교의 세로보 절취부에 피로균열이 발생 하였을 때 이에 대한 적절한 보수 보강 방법을 연구하기 위하여 실제로 피로균열이 발생한 철도교를 연구대상으로 실물크기의 가로보-세로보 바닥틀 모형을 제작하고, 세로보의 절취부 및 균열부에 스톱 홀 보수, 덧댐판 보강, 연결판 보강, 브라켓 보강 등 보수 보강 방법을 적용하여 실내실험을 수행하였다. 그 결과 제일 효과적인 보강 방법으로는 세로보의 상부플랜지와 하부플랜지에 연결판과 브라켓을 설치하는 것이고, 균열 선단에 스톱 홀을 뚫는 방법은 보조적인 방법으로 사용할 수 있다는 결론을 얻었다. 그리고 균열 길이가 어느 정도 길 경우에는 복부판에 덧댐판을 설치할 필요가 있다.

• 대한통합의학회지
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• 제5권3호
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• pp.21-28
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• 2017

Purpose: The purpose of this study was to investigate the effects of three exercise programs on forward head posture. Methods: Ninety-five individuals were recruited to assess the of the pectoralis minor muscle. Of these, 36 individuals with pectoralis minor muscles were selected and randomly divided into three groups: a functional massage group, a stretching group, and a stretching and muscle strengthening group. The exercise program consisted of sessions four times per week for two weeks. The length of pectoralis minor and the activity of the trapezius muscles were measured using electromyography. Forward head posture was assessed using the craniovertebral angle (CVA) and the cranial rotation angle (CRA) pre-, during and post-treatment. Result: Significant improvements were observed in pectoralis minor length, CRA, and CVA post-treatment in all groups (p<0.05, p<0.01, p<0.001). However, only the activity of the lower trapezius demonstrated a statistically significant difference post-treatment. There were no significant differences between the groups. Conclusion: The findings of this study suggest that all three exercise programs were effective in improving forward head posture and the length of pectoralis minor post-treatment.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.313-323
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• 2020

Non-destructive tests are commonly used in construction industry to access the quality and strength of concrete. However, till date there is no non-destructive testing method that can be adopted to evaluate the bond condition of reinforced concrete beams. In this regard, the presented research work details the use of ultra-sonic pulse velocity test method to evaluate the bond condition of reinforced concrete beam. A detailed experimental research was conducted by testing four identical reinforced concrete beam samples. The samples were loaded in equal increments till failure and ultra-sonic pulse velocity readings were recorded along the length of the beam element. It was observed from experimentation that as the cracks developed in the sample, the ultra-sonic wave velocity reduced for the same path length. This reduction in wave velocity was used to identify the initiation, development and propagation of internal micro-cracks along the length of reinforcement. Using the developed experimental methodology, researchers were able to identify weak spots in bond along the length of the specimen. The proposed method can be adopted by engineers to access the quality of bond for steel reinforcement in beam members. This allows engineers to carryout localized repairs thereby resulting in reduction of time, cost and labor needed for strengthening. Furthermore, the methodology to apply the proposed technique in real-world along with various challenges associated with its application have also been highlighted.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.559-565
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• 1998

Flexural tests on 2.4m long reinforced concrete beams with epoxy-bonded GFRP plates are reported in these tests. The selected experimental variables are strengthening plate length, plate thickness, plate width and the method of anchoring the plate ends. The effects of these variables in overall behavior are discussed. The results generally indicate that the flexural strength of strengthened beams is increased. The ductile behavior of tested beams in inversely proportional to the plate thickness, plate width. The use of an U-jacket plate provided a proper anchorage system and improved the ductility of beams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.137-140
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• 2005

This paper focuses on the premature failure of RC beams bonded with FRP. A number of failure modes for RC beams bonded with FRP have been observed in numerous experimental studies during past decade. Particularly, Rip-off failure and Debonding failure were majority failure modes in RC beams bonded with FRP. Rip-off failure occurred at the plate end due to high interfacial shear and normal stresses however Debonding failure was caused by the yielding of reinforcing bar and the increasing of shear deformation in shear span. On the basis of premature failure mechanism in RC beams bonded with FRP, Basic strengthening length and Premature failure criteria were derived

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.141-144
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• 2005

Rip-off failure and Debonding failure were commonly reported premature failure modes. The main reasons of premature failure in RC beams bonded with FRP were strengthening length and the reinforcement ratio. in this study, On the basis of premature failure mechanism in RC beams bonded with FRP, premature failure criteria were proposed. Also It was verified that Rip-off failure and Debonding failure occured according to premature failure criteria

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.335-338
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• 2003

Flexural test and parametric study by FEM analysis on 6.0m long reinforced concrete beams strengthened by GFRP are reported in these tests. The selected variables are strengthened plate length, plate thickness. The effects of these variables are discussed. The results generally indicate that the flexural strength of strengthened beams is increased. The results of FEM analysis show that the more strengthening GFRP is the more stress of GFRP is decrease when failure mode is peeling failure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.515-520
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• 2001

This study discusses the flexural performance of rehabilitated composite sections, consisting originally of R/C beams and subsequently strengthened by, Hybrid Fiber Reinforced Polymers(FRPs) and adhesives. Experimentations were peformed with 8 specimens to compare the rehabilitated effect of the length of FRPs, 2plies of FRPs, and 3plies of FRPs. The results show that the increase of the FRP strengthening length is effective on the flexural capacity and strength. Also, R.C beams retrofitted with hybrid FRPs are more effective on the increase of flexural capacity, strength, stiffness, and ductility than with a single kind of FRPs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.531-536
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• 2003

It is generally known that RC flexural members strengthened by GFRP(Glass Fiber Reinforced Polymers) tend to be failed by premature bond failure near the flexural-shear cracks happened at the mid-span of beams. It is therefore strongly recommended that premature bond failure must be avoided to insure the intended strengthening effects sufficiently. The various methodologies such as increasing bonded length of GFRP and bonding details including U-shape wrappings and epoxy shear-keys are examined in this study. The bonded length of GFRP are calculated based on the assumed bond strengths of epoxy saturating resin. Total six half scale RC beam specimens were constructed and tested to investigate the effectiveness of each methodologies to prevent the bond failure of GFRP. Test results of each specimens are discussed in this paper.

• Geomechanics and Engineering
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• 제18권5호
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• pp.503-513
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• 2019

In the present, the liquefaction potential of fiber-reinforced sandy soils was investigated through the energy-based approach by conducting a series of strain-controlled cyclic simple shear tests. In the tests, the effects of the fiber properties, such as the fiber content, fiber length, relative density and effective stress, and the test parameters on sandy soil improvement were investigated. The results indicated that the fiber inclusion yields to higher cumulative liquefaction energy values compared to the unreinforced (plain) ground by increasing the number of cycles and shear strength needed for the liquefaction of the soil. This result reveals that the fiber inclusion increases the resistance of the soil to liquefaction. However, the increase in the fiber content was determined to be more effective on the test results compared to the fiber length. Furthermore, the increase in the relative density of the soil increases the efficiency of the fibers on soil strengthening.