• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.786-789
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• 2004

Corrosion of reinforced concrete structures in marine environment is one of the most important mechanism of deterioration. However, conventional rehabilitation techniques in tidal zone, which consist of removing delaminated areas of concrete, cleaning affected steel and patching with portland cements mortar, have proven to be ineffective for marine structures. Also, repairs are often repeated every several years. The purpose of this report is to announce appropriate repair method of highway bridge damaged by chloride attack in marine environment (application of cathodic protection) using FRP and antiwashout underwater mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.217-218
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• 2010

This study presented the analytical evaluation model effective in the concrete structure repaired with a patching material. The model considered the effect of the repair material on carbon dioxide penetration into the repaired concrete as evaluating the remaining service life of the CO2-deteriorated concrete structure after repair. The diffusion profiles of carbon dioxide as well as the carbonated concrete were effectively able to be modelled with analytical method based on Fick's 1st diffusion law.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.115-118
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• 2000

The development of high-strength fibers such as boron/epoxy and carbon/epoxy and adhesives has made it possible to repair cracked metallic plates by bonding reinforcing patches to the plate over the crack. In this study, aluminum 6061-T6 alloy plates with the high strength are applied to specimens with a cracked bolt hole to study the effect of diverse patch materials on the fatigue behavior of this structure. Additionally, the observation of the effort of different patch sizes on the specimen was performed. The results shows that the patch repair can improve the static strength by about 17% and the fatigue life by 200% compared with non-repaired case. And it was also revealed that the patching method along to crack growth direction is mort efficient in cost and weight reduction.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.599-608
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• 2002

Finite element analysis for the stress intensity factor (SIF) at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels is developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior at the inclined crack. In order to investigate the crack growth direction, maximum tangential stress (MTS) criterion are used. Also, this paper is to study the performance of the effective bonded composite patch repair of a plate containing an inclined central through-crack. 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. We report the results of finite element analysis on the stiffener locations and crack slant angles and discuss them in this paper. The research on cracked structure subjected to mixed mode loading is accomplished and concludes that more work using a different approaches is necessary. The authors hope the present study will aid those who are responsible for the repair of damaged aircraft structures and also provide general repair guidelines.

• Journal of Chest Surgery
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• v.27 no.1
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• pp.24-30
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• 1994

Eighteen infants with a large ventricular septal defect[VSD] underwent primary surgical repair from January 1986 to December 1992. Operation was done because of failure to thrive, medically intractable heart failure, recurrent pneumonia, increased pulmonary vascular resistance[PVR]. Four patients[22.2%] died in the early postoperative period. Relief of heart failure and normalization of growth and weight gain was evident in all survivor. There was no late postoperative death. The results of primary surgical repair of VSD in infancy are compared with those of palliative pulmonary artery banding[PAB] and of VSD closure after PAB. Twenty-seven patients with isolated VSD or with VSD associated with atrial septal defect, patent ductus arteriosus, or coarctation of the aorta underwent initial palliative PAB. There were 3 early postoperative deaths[11.1%]. Severe elevation of PVR persisted in two patients. Closure of VSD and pulmonary artery debanding was done in twenty patients, with 2 early postoperative deaths[10.0%]. Placement of the PAB too close to the pulmonary annulus necessitated trasannular patching in one patient, but any problem caused by migration of the band was not developed. It is concluded that primary surgical repair of VSD in infancy is reasonable and that PAB is indicated only for those patients less than 6 months old with a complicated defect or in an emergency situation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.226-234
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• 2011

The service life of concrete structures exposed to a marine environment can be extended by controlling the amount of chloride in cover concrete. Patching is one of the appropriate maintenance techniques for chloride contamination. Chloride-contaminated cover concrete is removed and replaced with sound one. It can provide less risk of corrosion of steel, so that the structure can be maintained for required service life. In this study, a quantitative assessment of the service life subjected to the chloride attack is proposed to determine the effective repair options such as repair depth, repair material and timing of repair. The Crank-Nicolson based finite difference formulation from Fick's second law is proposed to predict the profiles of chloride ion in a repaired concrete structure, considering ingress of chloride from outer and redistribution of residual chloride from the substrate concrete. Therefore, the repair application times and maintenance cost for the target service life can be estimated. Finally, the numerical examples are presented to ensure its applicability.

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

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.411-418
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• 2012

In this study, behavior of unpatched and patched cylindrical shells with through-wall cracks has been estimated using numerical experiments, and patching effect of them has been investigated according to various patching parameters. To show credibility of numerical models considered, two ways such as h- and p-methods have been adopted. Also, domain integral method and virtual crack extension method have been considered to calculate energy release rates based on linear elastic fracture mechanics. For examples, the unpatched cylindrical shells with circumferential cracks under remote tension have firstly been analyzed to show the validity of finite element modeling with h-method or p-method, and then the results have been compared with literature values published. Next, the sensitive analysis of patch repaired problems in terms of thickness of patch and adhesive, shear modulus of adhesive, composite material type of patch, crack length, etc. has been carried out.

• Journal of Chest Surgery
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• v.28 no.12
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• pp.1107-1112
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• 1995

Between December 1993 and December 1994, fifty-eight percent of the mitral valve patients[33/57 had undergone mitral valve repair. Their mean age was 49[SD-16 years[range 11 - 75 and they were consisted with 15 males and 18 females. The causes of mitral disease in 33 patients were classified as follows: 19 cases[58% were degenerative, 9[27% were rheumatic, 3[9% were congenital and 2[6% were infectious. Carpentier`s functional classification was consisted with Class I 4 cases[12% , II 25 [76% and III 4 [12% . Surgical techniques included prosthetic annuloplasty in 32 cases[97% , leaflet resection in 16[48% , chorda shortening in 13[39% , chorda transfer in 9[27% , new chorda formation in 7[21% , commissurotomy in 7[21% , leaflet mobilization in 4[12% , chorda resection in 3[9% , papillary muscle splitting in 2[6% , cleft repair in 2[6% , leaflet patching in 1[3% and vegetation removal in 1[3% . Average number of mitral anatomical lesions per patient was 3.3 and We used average 3.0 procedures upon mitral valve apparatus per patient. Intraoperative transesophageal echocardiography was carried out in 27 patients[82% for providing an immediate and accurate assessment of the adequacy of the reconstruction before closure of the chest. Operative mortality was absent. The mean functional class[NYHA was 2.87 preoperative and improved to 1.03 postoperatively. Postoperative Doppler echocardiography showed much improvement from grade II MR[5 , grade III[5 , grade IV[21 to no MR[26 , only trace MR[3 , grade III MR[2 . Postoperative mean mitral valve area was 2.4$\pm$0.6cm2[range 1.5 - 4.0 . We conclude that cautiously evaluated mitral valve reconstruction is stable and predictable operation with minimal postoperative left ventricular dysfunction.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.77-85
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• 2018

PURPOSES : The purpose of this study was to develop an urgent road-repair system and perform a field applicability test, as well as discover the optimum mix design for machine applications compared to the optimum mix design for lab applications. METHODS : According to reviews of the patent and developed equipment, self-propelled and mix-in-place equipment types are suitable for urgent pavement repair, e.g., potholes and cracks. The machine-application mix design was revised based on the optimum lab-test mix design, and the field application of a spray-injection system was performed on the job site. The mixture from the machine application and lab application was subjected to a wet-track abrasion test and a wheel-tracking test to calibrate the machine application. RESULTS and CONCLUSIONS : This study showed that the binder content could differ for the lab application and the machine application in the same setting. Based on the wet-track abrasion test result, the binder contents of the machine application exceeded the binder contents of the lab application by 1-1.5% on the same setting value. Moreover, the maximum dynamic stability value for the machine application showed 1% lower binder contents than the maximum lab-application value. Collectively, the results of the two different tests showed that the different sizes and operating methods of the machine and lab applications could affect the mix designs. Further studies will be performed to verify the bonding strength and monitor the field application.