• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1031-1036
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• 2000

In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.61-75
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• 2024

Strengthening of hollow structural sections using through-bolts is a cost-effective and straightforward approach. It's a versatile method that can be applied during both design and service phases, serving as a non-disruptive and budget-friendly retrofitting solution. Existing research on axially loaded hollow sections T-joints has demonstrated that this technique can amplify the joint strength by 50%, where single bolt could enhance the strength of the joint by 35%. However, there's a gap in understanding their use for K-joints. As the behavior of K-joints is more complex, and they are widely existent in structures, this study aims to bridge that gap by conducting comprehensive parametric study using finite element analysis. Numerical investigation was conducted to evaluate the effect of through bolts on K-joints focusing on using single through bolt to achieve most of the strengthening effect. A full-scale parametric model was developed to investigate the effect of various geometric parameters of the joint. This study concluded the existence of optimal bolt location to achieve the highest strength gain for the joint. Moreover, a rigorous statistical analysis was conducted on the data to propose design equations to predict optimal bolt location and the corresponding strength gain implementing the verified by finite element models.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.92-95
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• 2004

The flexural strengthening effect of the RC beam strengthened with CFS under pre-loading condition was studied here. The beams were additionally strengthened at the each end with U type wrapping using the same CFS. Main variables considered were number of CFS plies(1,2) and pre-loading values(30,50,$70\%$ of the yield load of the control beam). The flexural strengthening effect was investigated through comparing the yield load, ultimate load, and ductility index of the specimens.

• 대한정형도수물리치료학회지
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• 제24권1호
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• pp.67-75
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• 2018

Background: The purpose of this study was to investigate the effect of pressure distribution on the both foots with gluteus medius muscle intensive strengthening exercise in 4week. Methods: The purpose of this study was to investigate the effect of gluteus medius muscles strengthening exercise on the pressure distribution of the foot in 20 healthy adults. Four gluteus medius muscles strengthening exercise programs were conducted three times a week for four weeks. The pressure distribution changed of the right and left foot parts of the experimental group and the control group were measured and analyzed. Results: There was a significant difference in F1, F2, M1, M2, and H1 among the pressure distribution of the right foot of the experimental group (p<.05). There was a significant difference in F1, M1, M2, H1 and H2 among the pressure distributions of the left foot of the experimental group (p<.05). There was a significant difference in H1 among the pressure distribution of the right foot of the control group (p<.05). There was no significant difference in the pressure distribution of the left foot region of the control group (p>.05). There was a significant difference in H1 among the pressure distribution of the right foot between the group (p<.05). There was a significant difference in M2, H1 among the pressure distribution of the left foot between the group (p<.05). Conclusions: In the healthy adults, it was confirmed that the application of the gluteus medius muscles strengthening exercise had an effect on the weight shift during the walking due to the overall foot balance and the pressure distribution change of the foot part.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.256-262
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• 2022

본 연구의 목적은 실험을 통하여 FRP를 이용한 철근콘크리트 부재의 표면매립 전단보강 효과를 규명하는 것이다. 연구목적을 달성하기 위하여, 3개의 철근콘크리트 T형 보를 제작하고 이중 두 개의 보에 대해서 표면매립 보강방법으로 FRP를 전단보강한 뒤 실험을 통하여 보강효과를 규명하였다. 실험에서 두 가지의 전단보강방법을 고려하였는데, 첫째 충분한 매립길이를 가진 표면매립 (NSM) 보강, 둘째 다소 짧은 표면매립길이를 가지지만 추가의 표면부착 (EB) 보강을 한 경우이다. 연구결과, FRP strip을 이용한 표면매립길이를 플랜지 하부까지 길게 확보할 경우에는 충분한 전단보강효과가 발휘되는 것으로 나타났다. 반면에 충분한 매립길이가 확보되지 않은 경우에는 FRP sheet로 추가 보강하더라도 전단보강효과가 나타나지 않는 것으로 나타났다.

• 근관절건강학회지
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• 제7권2호
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• pp.294-308
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• 2000

This study was conducted to test the effect of brisk walking & muscle strengthening exercise program on bone mineral density(BMD) of the lumbar & femur in rheumatoid arthritis women. Research design was a quasi-experimental study of non-equivalent control group pretest-posttest design(16 weeks). 14 for the experimental group and 14 for the control group were selected from the outpatients on rheumatoid arthritis clinic of Dong-A University Hospital. The experimental group underwent 16 weeks of brisk walking and muscle strengthening exercise. Bone mineral density was measured before and after 16 weeks of exercise by DXA at lumbar spine, femoral neck, Ward's triangle and trochanter. The results were summarized as follows : 1. BMD of the lumbar spine in experimental group who carried out the brisk walking and muscle strengthening exercise was not significantly increased after 16weeks and there was no significant difference between experimental and control group(U=70.00 p>.05). 2. BMD of the femoral neck in the experimental group who carried out the brisk walking and muscle strengthening exercises was significantly increased after 16 weeks(Z=-2.901 p<.01). But, there was no significant difference between experimental and control group(U=83.00 p>.05). 3. BMD of the femoral Ward's triangle in the experimental group who carried out the brisk walking and muscle strengthening exercises was significantly increased after 16 weeks (Z=-2.355 p<.05). But, there was no significant difference between experimental and control group(U=86.00 p>.05). 4. BMD of the femoral trochanter in experimental group who carried out the brisk walking and muscle strengthening exercise was not significantly increased after 16weeks and there was no significant difference between experimental and control group(U=75.00 p>.05). These results suggest that brisk walking and muscle strengthening exercise program has an effect on promoting bone mineral density of femoral neck and Ward's triangle in rheumatoid arthritis women.

• 콘크리트학회논문집
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• 제16권5호
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• pp.667-675
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• 2004

본 논문은 CFRP 격자 보강재로 보강한 콘크리트 슬래브의 파괴형태와 보강설계기준에 대한 연구이다. 실험 연구에서 채택한 시험변수로는 CFRP 격자 보강재의 양, 보강 모르타르의 깊이, 앵커핀의 유무, 압축부 보강 등이다. 연구에 의하면 CFRP 격자 섬유 보강량에 따라 파괴형태가 다르게 나타났는데 낮은 보강수준에서는 FRP 격자의 인장 파단파괴를 보였고 보통의 보강정도에서는 격자층 계면전단파괴가 발생하였다. 높은 보강량을 가진 슬래브에서는 사인장전단파괴 형태를 나타냈다. 보강 효과는 FRP 격자 보강재의 양이 증가할수록 증대하였으나 취성 전단파괴에 의해 연성은 감소되었다. 따라서 FRP 격자 보강량을 제한함으로써 갑자기 하중 지지력을 상실하는 전단파괴를 피할 수 있다. 파괴형태 중 CFRP 파단파괴가 바람직한데 그 이유는 섬유파단 후에도 극한상태에서 보강 전 슬래브의 하중지지력과 연성을 가지고 있기 때문이다. 마지막으로 본 논문은 CFRP 격자섬유보강설계기준과 과정을 제시하고 있다.

• Structural Monitoring and Maintenance
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• 제7권3호
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• pp.233-259
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• 2020

Using bonded fiber-reinforced polymer laminates for strengthening wooden structural members has been shown to be an effective and economical method. In this research, properties of suitable composite materials (sika wrap), adhesives and two ways of strengthening beams exposed to bending moment are presented. Passive or slack reinforcement is one way of strengthening. The most effective way of such a strengthening was to place reinforcement laminates in the stretched part of the wooden beam (lower part in our case), in order to investigate the effectiveness of externally bonding FRP to their soffits. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the wooden beam, the sika wrap composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. This research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-wooden hybrid structures. The results showed that the use of the new strengthening system enhances the performance of the wooden beam when compared with the traditional strengthening system.

• 대한물리치료과학회지
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• 제18권3호
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• pp.79-86
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• 2011

Background : The purpose of this study was to investigate on the ankle pain, Range of Motion(ROM) and balance ability with old man have fall down experience used to ankle strengthening exercise for 6 weeks. We introduced ankle strengthening exercise in this study in order to recover the pain, ankle ROM and balance ability. Methods : Twenty-four old mans have fall down experience were included for the study. Among them, twelve old mans(experimental group) were ankle strengthening exercise and physical science methods(H/P, TENS, U/S), another twelve old mans(control group) were treated by physical science methods(H/P, TENS, U/S). Each group made use of Visual Analogue Scale(VAS) to pain and goniometer to ankle ROM and Berg Balance Test(BBS) to balance ability to compare the possible changes of pain, ROM and balance ability in two groups after treatment. Results : In experimental group, pain reduced, ankle ROM has increased in dorsi-flexion, plantar-flexion and balance ability has increased for 6 weeks. In control group, pain reduced, ankle ROM has not changed in dorsi-flextion, plantar-flextion and balance ability has not changed for 6 weeks. Conclusion : According to the results, we concluded that ankle strengthening exercise for 6 weeks is effective for reducing pain and increasing ankle ROM and balance ability. Therefore, we thought the old man have fall dawn experience need ankle strengthening exercise for prevention repeatedly fall down.

• Computers and Concrete
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• 제22권2호
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• pp.133-142
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• 2018

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.