• Title/Summary/Keyword: material strengthening

Search Result 397, Processing Time 0.021 seconds

A Study on Prevent Delamination of Strengthening Material (보강재의 탈락 방지 방안 연구)

  • 한만엽;백승덕
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 1998.10b
    • /
    • pp.809-814
    • /
    • 1998
  • Recently many cases that using strengthening method with a steel plate or carbon-fiber sheet in a construction field are increasing. In this reason, it is demanded that developing a plan of preventing delamination of strengthening material. So in this research, for the case of strengthening method of steel plate, it is made use of notch and anchor bolt and for the case of carbon fiber sheet, it is made use of notch, anchor bolt, line anchor and shear strengthening. After all the cases were applied, we made 15 specimen beams. The beams was measured and analyzed about the behavior property of strengthened beams, the ability strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods results in almost same value until the yield load, and it wasn't quite different from the theoretical value. But for the case of increasing rate from the yield load and maximum load, comparing with the existing method, the new strengthening methods are proved to be profitable about the safety.

  • PDF

Numerical Analysis on External Strengthening Effects in Aged Structures (사용중인 구조물의 보강효과에 대한 해석적 연구)

  • 신승교;임윤묵;김문겸;박동철
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2002.05a
    • /
    • pp.455-460
    • /
    • 2002
  • In this study, a numerical analysis that can effectively predict the effect of strengthening of cracked flexural members is developed using axial deformation link elements. Concrete and interface between concrete and repair material are considered as quasi-brittle material. Reinforcing bars and reinforcing steel plates are assumed to perform as elasto-plastic materials. Unloading behavior of axial deformation link element is implemented. In the developed numerical model, a flexural member is intentionally cracked by pre-loading, then, the cracked member is repaired using extra elements, and reloaded. The results from analysis of repaired flexural members agrees well with available experiment results. Also, it was shown that the effect of strengthening and the change of failure mode with respect to the time for strengthening and thickness of repair materials. Based on the results, it was determined that the developed numerical model has a good agreement for determining failure modes and effect of strengthening in cracked flexural members. By utilizing the developed numerical analysis, the time and dimension of external strengthening in an existing cracked flexural member with predition of failure mechanism can be determined.

  • PDF

A Development on Method of Strengthening Design for the Different Status of Damages (손상상태를 고려한 부재의 보강설계법 개발)

  • 한만엽;이성준
    • Journal of the Korea Concrete Institute
    • /
    • v.12 no.1
    • /
    • pp.69-77
    • /
    • 2000
  • Recently, many strengthening methods are developed to repair damaged structures, when the original structure is under loading, which causes the difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and the amount of strengthening which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. The results show that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

A Study for Numerical Procedure of Strengthening Capacity in Field Structure (사용중 보강되는 부재의 보강설계법 연구)

  • 한만엽;이원창
    • Journal of the Korea Concrete Institute
    • /
    • v.11 no.3
    • /
    • pp.13-21
    • /
    • 1999
  • Recently, many strengthening methods are developed to repair damaged structures, especially, steel plate or carbon fiber sheet bonding methods are widely used. For the bonding methods, the strengthening materials are bonded when the original structure is under loading, with causes the difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and program which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. In order to verify the validity of the theory and the program, a test result is referred and compare with the results and it is showed that the calculated values are almost same as the referred data and finally proved that the program is reliable. The results showed that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

The Strengthening Desing Method Considering Damages of Structure (구조물의 손상 상태에 따른 보강설계법 연구)

  • 한만엽;이택성
    • Journal of the Korea Concrete Institute
    • /
    • v.11 no.3
    • /
    • pp.35-45
    • /
    • 1999
  • Recently, many strengthening methods are developed to repair damaged structures, especially, steel plate or carbon fiber sheet bonding methods are widely used. For the bonding methods, the strengthening materials are bonded when the original structure is under loading, which causes difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and program which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. In order to verify the validity of the theory and the program, a test result is referred and compared with the results and it is showed that the calculated values are almost same as the referred data and finally proved that the program is reliable. The results showed that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

Theoretical Analysis of Interface Debonding on the Strengthened RC Bridge Decks (성능향상된 RC 바닥판의 계면파괴 해석)

  • 오홍섭;심종성
    • Journal of the Korea Concrete Institute
    • /
    • v.14 no.5
    • /
    • pp.668-676
    • /
    • 2002
  • Especially, when orthotropic material such as uni-dierectionally woven Carbon Fiber Sheet, resisting only the unidirectional tension, is used to strengthening bridge deck, the direction and width of the strengthening material should be considered very carefully. Thus, analysis of the failure characteristics and the premature failure mechanism of the strengthened decks based on the test results are required. In this study, the premature failure due to the interface debonding of strengthening material of the strengthened deck slab are inquired into failure mechanism through both experiments results and analyses with prototype strengthened deck specimens using carbon fiber sheet. From the test results, interface debonding of strengthening material is occured at the crack face

Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Material Property of Sprayed FRP - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - Sprayed FRP를 구성하는 재료특성에 관한 연구 -)

  • Lee, Li-Hyung;Lee, Kang-Seok;Son, Young-Sun;Byeon, In-Hee;Lim, Byung-Ho;Na, Jung-Min
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2006.11a
    • /
    • pp.141-144
    • /
    • 2006
  • The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of Sprayed FRP, this study carried out tensile tests of the material specimens which are changed with the combinations of various variables such as the length of shot fiber and mixture ratio of shot fiber and resin. These variables are set to have the material strength equal to one layer of the FRP sheet. As a result, the optimal length of glass and carbon shot fibers were derived into 3.8cm, and the optimal mixture ratio was also deriver into 1:2 from each variable. And also, the thickness of Sprayed FRP to have the strength equal to one layer of FRP sheet was finally calculated.

  • PDF

Analysis of Strengthening Veriables for Strengthened Bridge Decks by Externally Bonded Sheet (보강판으로 외부부착 보강된 교량 바닥판의 성능향상을 위한 변수 해석)

  • 심종성;오흥섭
    • Journal of the Korea Concrete Institute
    • /
    • v.14 no.4
    • /
    • pp.556-565
    • /
    • 2002
  • The concrete bridge decks on the main girder will usually develop initial cracks in the longitudinal or the transverse direction due to dry shrinkage and temperature change, and as the bridge decks age the crack will gradually develop in different directions due to repeated cyclic loads. The strengthening direction of the concrete bridge deck is a very important factor in improving proper structural behavior. Therefore, in this study, theoretical analyses of strengthened bridge decks were performed using the nonlinear finite element method. To improve the accuracy of the analytical result, boundary conditions and material property of strengthening material was simulated by laboratory condition and test results, respectively. The effect of the strengthening direction and the amount of strengthening material were estimated and compared to the experimental results. The efficiency of the strengthened bridge decks by strengthening variables such as the amount, width and thickness of CFS was observed.

Evaluation of Shear Strength in SFRC Beam without Stirrups Considering Steel Fiber Strengthening Factor (강섬유 보강계수를 고려한 전단보강 되지 않은 SFRC 보의 전단내력 평가)

  • Lee, Hyun-Ho
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.8 no.2
    • /
    • pp.213-220
    • /
    • 2004
  • The purpose of this study is to evaluate the shear strength of SFRC beam that has no stirrups by steel fiber strengthening factor. To achieve the goal of this study, two stage investigation, which is material and member level, is studied with literature and experimental side. From the reviewing of previous researches and analyzing of material and member test results, strengthening parameter of SFRC is defined as steel fiber coefficient. Based on above results, steel fiber strengthening factor is proposed. And by reviewing the proposed equation of shear strength estimation, equation of Shin was well estimated the shear strength of SFRC beams. Therefore, shear strength equation of SFRC, which is composed by Shin's Eq. and steel fiber strengthening factor, is proposed by regression analysis of test results.

Regarding a Shear Strengthening of an Epoxy Mortar Panel for RC Beam Without Shear Strengthening Reinforcing Bar (전단보강철근이 없는 RC보에 대한 에폭시 모르타르 패널의 전단보강에 관한 연구)

  • Lee, Sang-Ho;Cho, Min-Su;Heo, Jae-Sang
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.12 no.3
    • /
    • pp.135-146
    • /
    • 2008
  • In this study, the effect of epoxy mortar panel as the shear strengthening material of reinforced concrete beam is investigated by loading test. The main variables are the kind of strengthening material, the amount of reinforcement and the spacing of CFS(Carbon Fiber Sheet) stirrups. The design method to use epoxy mortar panel as shear strengthening of reinforced concrete beam took the shear capacity as the form of the sum of $V_c$, $V_s$, $V_{sheet}$ and $V_p$. By making a comparison between the values calculated by the proposed shear strength prediction formula and those from the loading test results, the mean value was 1.10 and the standard deviation was 8.16%.