• Structural Engineering and Mechanics
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• 제64권3호
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• pp.323-328
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• 2017

This paper presents a three-dimensional finite element method analysis of repairing plate with bonded composite patch subjected to tensile load. The effect of the corrosion on the damage of the adhesive (FM73) in the length of two horizontal cracks on the both sides is presented. The obtained results show that the crack on the left side creates a very extensive area of the damaged zone and gives values of the stress intensity factor (SIF) higher than that on the right side. We can conclude that the left crack is more harmful (dangerous) than that on the right side.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.635-642
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• 1997

This research focused on the development of concrete overlay and test, which was conducted at 88 Highway 105k, 2 lanes of 290 m. The field application test consists of 6 cm and 10 cm bonded concrete overlay and 25 cm unbonded concrete overlay, using the slag cement for opening lanes for traffic early. The overlay were placed in a day. The whole period of traffic closing wes 8 day and it was reopened to traffic after concrete overlay has cured for 3 day. 5 cracks were founded when the field test section was investigated after 1 month, but all these may not make significant problems to overlay because these initiated and growed at the same line of repair section. The rideability and skid resistance become much better like in the new pavement after overlay. The structural capacity against deflection was much. which were verified by FWD(Falling Weight Deflectometer). The field test section is being used in a good condition and the results of field application and pavement performance analysis are encouraging. This rehabilitation methods may be adopted in Korea after a more field performance verifications.

• 한국도로학회논문집
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• 제17권3호
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• pp.85-95
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• 2015

PURPOSES : Recently, bonded concrete overlay has been used as an alternative solution in concrete pavement rehabilitation since its material properties are similar to those of the existing concrete pavements. Deteriorated concrete pavements need rapid rehabilitation in order to prevent traffic jams on Korean expressways. Moreover, speedy and effective repair methods are required. Therefore, the use of bonded concrete overlay with ultra-rapid hardening cement has increased in an effort to reopen promptly the expressways in Korea. However, mobile mixer is required for ultra-rapid hardening cement concrete mixing in the construction site. The use of mobile mixer causes various disadvantages aforementioned such as limitation of the construction supply, open-air storage of mixing materials, increase in construction cost, and etc. In this study, therefore, hydration accelerator in-situ mixing on polymer modified concrete produced in concrete plant is attempted in order to avoid the disadvantages of existing bonded concrete overlay method using ultra-rapid hardening cement. METHODS : Bonded concrete overlay materials using ultra-rapid hardening cement should be meet all the requirements including structural characteristics, compatibility, durability for field application. Therefore, This study aimed to evaluate the application of hydration accelerator in-situ mixing on polymer modified concrete by evaluating structural characteristics, compatibility, durability and economic efficiency for bonded concrete overlay. RESULTS : Test results of structural characteristics showed that the compressive, flexural strength and bond strength were exceed 21MPa, 3.15MPa and 1.4MPa, respectively, which are the target strengths of four hours age for the purpose of prompt traffic reopening. In addition, tests of compatibility, such as drying shrinkage, coefficient of thermal expansion and modulus of elasticity, and durability (chloride ions penetration resistance, freezing-thawing resistance, scaling resistance, abrasion resistance and crack resistance), showed that the hydration accelerator in-situ mixing on polymer modified concrete were satisfied the required criteria. CONCLUSIONS : It was known that the hydration accelerator in-situ mixing on polymer modified concrete overlay method was applicable for bonded concrete overlay and was a good alternative method to substitute the existing bonded concrete overlay method since structural characteristics, compatibility, durability were satisfied the criteria and its economic efficiency was excellent compare to the existing bonded concrete overlay methods.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.361-370
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• 2017

Through the use of finite element analysis and acoustic emission techniques we have evaluated the interfacial failure of a carbon fiber reinforced polymer (CFRP) repair patch on a notched aluminum substrate. The repair of cracks is a very common and widely used practice in the aeronautics field to extend the life of cracked sheet metal panels. The process consists of adhesively bonding a patch that encompasses the notched site to provide additional strength, thereby increasing life and avoiding costly replacements. The mechanical strength of the bonded joint relies mainly on the bonding of the adhesive to the plate and patch stiffness. Stress concentrations at crack tips promote disbonding of the composite patch from the substrate, consequently reducing the bonded area, which makes this a critical aspect of repair effectiveness. In this paper we examine patch disbonding by calculating the influence of notch tip stress on disbond area and verify computational results with acoustic emission (AE) measurements obtained from specimens subjected to uniaxial tension. The FE results showed that disbonding first occurs between the patch and the substrate close to free edge of the patch followed by failure around the tip of the notch, both highest stress regions. Experimental results revealed that cement adhesion at the aluminum interface was the limiting factor in patch performance. The patch did not appear to strengthen the aluminum substrate when measured by stress-strain due to early stage disbonding. Analysis of the AE signals provided insight to the disbond locations and progression at the metal-adhesive interface. Crack growth from the notch in the aluminum was not observed until the stress reached a critical level, an instant before final fracture, which was unaffected by the patch due to early stage disbonding. The FE model was further utilized to study the effects of patch fiber orientation and increased adhesive strength. The model revealed that the effectiveness of patch repairs is strongly dependent upon the combined interactions of adhesive bond strength and fiber orientation.

• 콘크리트학회논문집
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• 제12권3호
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• pp.103-114
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• 2000

Recently, the need for strengthening reinforced concrete and prestressed concrete structure is increasing, particularly when there is an increase in load requirements, a change in use, a degradation problem, or some design/construction defects. Therefore, use of composite materials for structural repair presents several advantages and has been investigated all over the world. In this paper, the reinforced concrete slabs with epoxy - bonded AFRP sheed were experimentally investigated. Experimental data on strength. stiffness, material strain, deflection and mode of failure of strengthened slabs were obtained, and comparisons between the different flexural reinforcing schemes and reinforced concrete slabs without AFRP sheets were made It can be concluded that flexural strength of RC slabs strengthened with AFRP has increased, and that ductility of strengthened slabs has decreased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.597-600
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• 2003

The development and maintenance of a sound bond are an essential requirements of concrete repair and replacement. The bond property of a bonded overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified. A standard or a verified bond strength measurement method is required at field for screening, selecting materials and quality control for overlay or repair materials. This study compares the nipple pipe direct tensile test, flexural adhesion test, and core pull-off test with their test results. Substantial differences in the failure stresses of three test methods were attributed to their different geometries and loading conditions. From these comparison and investigation, core pull-off test was relatively good because the coefficient of variation values were about 2%. It would be suitable for use in-situ because of its simplicity and accuracy.

• 비파괴검사학회지
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• 제29권6호
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• pp.525-533
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• 2009

Emphasis in the paper is placed on describing guided wave successes and challenges for applications in aircraft and composite materials inspection. Guided wave imaging methods discussed includes line of sight, tomography, guided wave C-scan, phased array, and ultrasonic vibration methods. Applications outlined encircles lap splice, bonded repair patch, fuselage corrosion, water loaded structures, delamination, and ice detection and de-icing of various structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.703-708
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• 1999

The concrete structure under fatigue load depresses in mechanical capability or breaks down finally because of the fatigue. So recently the study on strengthening methods using bonded steel plate is widely attended. Which could be constructed under use and without damaging the structure. The intention of this method is to increase the useability of the structure and to recover the strength. So application on fields are sharply increasing. In this study it is tried to develop strengthening methods using notches and anchor bolts which could supply the defect on falling off of the steel plate at the end.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.359-362
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• 2003

Carbon fiber sheet is attractive due to its good tensile strength, resistance to corrosion, and low weight. The strengthening of concrete structures with externally bonded carbon fiber sheets is increasingly being used for repair and rehabilitation of existing structures. However CFS strengthened beams break down under the service loads. As rupture strain is not reached ultimate value, reduction of the tensile strength is recommended. This study evaluate CFS tensile strength reduction factor which is required to analyze bending moment.

• 한국철도학회논문집
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• 제12권1호
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• pp.110-114
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• 2009

본 연구에서는 스카프 패취가 접착된 복합소재 샌드위치 적층판의 압축강도 회복특성을 평가하였다. 본 연구에서는 알루미늄 허니콤 심재와 CF1263 직조된 탄소/에폭시 면재를 갖는 틸팅열차차체에 적용된 샌드위치 시험편이 이용되었다. 샌드위치 시험편은 저속충격에 의해 손상을 가하고, 스카프 보수기법에 의해 보수되었다. 보수 후 CAI시험을 통해 충격 후 압축강도를 평가하여 강도회복정도를 정량적으로 규명하였다. 본 시험으로부터 단지 스카프 보수를 적용한 경우 약 72%정도의 강도를 회복하였고, 추가보수층 한층을 추가했을 경우 약 91%까지 강도를 회복시킬 수 있음을 확인하였다.