• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.337-340
• /
• 2006

Utilize several kinds of reinforcement fibers to control workability and surface crack in occasion of mortar used in dilapidated concrete section repair public law. Polypropylene or poly vinyl alcohol that is hydrophilic fiber etc. is used much usually with this reinforcement fiber. Reinforcement fiber does important action that control crack that enhances coherence between material and happens at dry contraction. In this study, wished to use Sepiorite that inorganic materials and affinity such as cement are excellent nature inorganic world fiber and improve repair mortar performance. In this study, as reinforcement fiber, wished to grasp physical characteristics that uses Sepioraiteu and happens this time and grasp application possibility of concrete's repair mortar.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2006.06a
• /
• pp.287-288
• /
• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.

• Advances in aircraft and spacecraft science
• /
• v.7 no.2
• /
• pp.151-168
• /
• 2020

The present study deals with the repair of composite structures by bonding composite patches. The composite structure is a carbon/epoxy laminate with stacking sequence [45/-45/0/90]S. The damaged zone is simulated by a central crack and repaired by bonding symmetrical composite patches. The repair is carried out using composite patches laminated from the same elemental folds as those of the cracked specimen. Three-dimensional finite element method is used to determine the energy release rate along the front of repaired crack. The effects of the repair technique used single or double patch, the stacking sequence of the cracked composite patch and the adhesive properties were highlighted on the variations of the fracture energy in mode I and mixed mode I + II loading.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.2
• /
• pp.68-75
• /
• 2018

In this study, to solve the problems of the conventional crack repair and injection method, high elasticity latex was used as the material of the storage tube to withstand the high pressure in the center part differently from the general port. When the repair solution was injected into the crack part, The TPS method was developed so that the air existing in the TPS can be discharged. In addition, a new infusion port in which a valve blocking the backflow of the remediation solution was installed at the injection port was developed and the physical characteristics of the port were analyzed. As a result of the evaluation, it was found that the filling rate of the remedial solution was improved compared to the existing ordinary injector method, and the cracks were completely filled in the test conditions. Compressive strength and tensile strength after repair showed about 20% decrease after repair in case of using ordinary injector method, while TPS method showed about 2~7% increase after repair. The results of this study showed that the injection port method using the elastic storage tube increased the injection performance and the quality after repair compared to the conventional injector method. The result of this study is expected to be utilized as the basic data for application and commercialization of the result to the practical structure.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.292-297
• /
• 2001

Composite patch repair of cracked aircraft structures has been accepted as one of improving fatigue life and attaining better structural integrity. Analysis for the stress intensity factor at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels are developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior. In order to investigate the crack growth direction, maximum tangential stress(MTS) criteria is used. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stress intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter including; composite patch thickness and stiffener distance. The research on cracked structure subjected to mixed mode loading is accomplished and it is evident that more work using different approaches is necessary.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.535-538
• /
• 2005

The problem of the crack which occures from the reinforced concrete structure. could be caused by the complexed factors. When the crack happen, it caused fatal blemish to manage and maintain the structure such as structural problem, licking, spalling, viewing Even though they study and work hard to solve this kind of problem in the world, there are no countermeasure for perfect prevention of crack. After the crack checked out, a method of repair-reinforcement has been sutdied and operated actively. In this experiment, studied durability of repair material. Experiment wave and durability of epoxy and urethane's were shown good result, and micro cement's durability displayed result that is not good. Result of a repeat tired experiment displayed result that micro cement is bad.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2007.04a
• /
• pp.129-132
• /
• 2007

In this study, for the establishment of the performance evaluation methods of repair material and method for reinforced concrete structure and the quality control standards of durability recovery method, the quantitative exposure data by exposure experiment under the coastal and normal atmosphere environment is accumulated and analyzed. Investigating and evaluating the result of exposure experiment during 54 months of exposure age under the coastal and normal atmosphere environment, Micro crack, swelling and spatting of surface coating material, crack of repair boundary parts and the great potential difference between repair part and non-repair part were somewhat generated. And the result shown that exposure specimen of coastal environment had lower electrode potential than exposure specimen of normal atmosphere environment.

• Magazine of the Korea Concrete Institute
• /
• v.12 no.6
• /
• pp.97-108
• /
• 2000

• Journal of the Korea Concrete Institute
• /
• v.16 no.1 s.79
• /
• pp.88-93
• /
• 2004

The objective of this study was to investigate applicability of epoxy injection method to cracked RC beams and structural behavior of repaired RC beams considering pre-loading conditions. For this purpose, five test beams were fabricated under two experimental variables. The main variables of this experimental study were pre-loading conditions and repair methods. The two pre-loading conditions were selected as $70\%$ and $90\%$ of nominal strength and the repair methods were to repair the cracked RC beams under free loading after crack and sustained loading. The comparative study was executed to evaluate effects of pre-loading conditions on the structural behavior of the cracked RC beams after crack-repair. The strains of reinforcement and concrete and deflections of beams at each loading step were measured and evaluated. As the results of this study, repair methods have much influence on structural behavior of epoxy injected RC beams and epoxy injection method for cracks of RC structures is appeared to be efficient.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.3
• /
• pp.33-39
• /
• 2007

This paper presents a detailed experimental study on the engineering and durability properties of nano mixed inorganic repair material with rehabilitation and enhancement of performance of concrete structure occur to crack. The performance of specimens was evaluated using bond strength, chloride ion ingress, carbonation and brine resistance. It was shown in the results of the experiments that it had a superior function in the bond strength under the standard and wet-dry condition of all the repair material. Moreover, it had a good function in the experiments for chloride ion ingress, carbonation and brine resistance. Judging from the above-mentioned results, it is expected to be used for the rehabilitation and enhancement of the performance of concrete structure.