• Journal of the Korean Geosynthetics Society
• /
• v.1 no.1
• /
• pp.53-61
• /
• 2002

Even though a lot of laboratory and field tests for asphalt pavements using geosynthetics have been conducted recently, any rational and systematic analysis for the economic efficiency of the asphalt pavement systems reinforced by using geosynthetics has not been proposed yet. In this study, the economic analysis considering the traffic characteristics for the glass fiber sheet reinforced asphalt pavement was performed using the Life Cycle Cost Analysis(LCCA) which is commonly used for the economic analysis technique. The economic efficiency for the glass fiber sheet reinforcement and the traffic characteristics was examined by applying the test results from the literature review to the economic analysis model.

• Journal of the Korean Wood Science and Technology
• /
• v.43 no.6
• /
• pp.861-867
• /
• 2015

The Compact Tension (CT) type test was performed in order to evaluate the fracture toughness performance of glass fiber-reinforced laminated timber. Glass fiber textile and sheet Glass fiber reinforced plastic were used as reinforcement. The reinforced laminated timber was formed by inserting and laminating the reinforcement between laminated woods. Compact tension samples are produced under ASTM D5045. The sample length was determined by taking account of the end distance of 7D, and bolt holes (12 mm, 16 mm, 20 mm) had been made at the end of artificial notches in advance. The fracture toughness load of sheet fiberglass reinforced plastic reinforced laminated timber was increased 33 % in comparison to unreinforced laminated timber while the glass fiber textile reinforced laminated timber was increased 152 %. According to Double Cantilever Beam theory, the stress intensity factor was 1.08~1.38 for sheet glass fiber reinforced plastic reinforced laminated timber and 1.38~1.86 for glass fiber textile reinforced laminated timber, respectively. That was because, for the glass fiber textile reinforced laminated timber, the fiber array direction of glass fiber and laminated wood orthogonal to each other suppressed the split propagation in the wood.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.6 no.1
• /
• pp.95-102
• /
• 2002

The flexural behavior of the reinforced concrete (RC) structure upgraded by external reinforcements was examined in this study. It is well known that the incorporation of carbon fiber sheet (CFS) with concrete is one of the most effective ways to strengthen the RC structure. Complete bonding is required between CFS and concrete in order to make the RC structure provide its full function until the time the Re structures serve. Many studies have reported that construction deficiencies have caused the debonding of the CFS from concrete before the RC structure with CFS reaches its ultimate capacity. This research took a systematic look at the failure mechanism, macroscopic load-deformation characteristics, the maximum load applied, and maximum bending moment when construction deficiencies exist. The results of the experiment conducted were compared with theoretically derived values. In the future, the results of this investigation will help minimize the factors of construction deficiencies, which may occur when CFS is used to reinforce a RC structure. The experiment was manipulated with steel reinforcement ratio and piles of CFS on a total of 14 beams ($20cm{\times}30cm{\times}240cm$). The results showed that internal moment capacity increased even when construction deficiencies existed. However, RC structures with CFS in the field still contain a considerable level of potential risks.

• Magazine of korean Tunnelling and Underground Space Association
• /
• v.1 no.2
• /
• pp.59-71
• /
• 1999

Recently, many deformations in tunnel such as crack and leakage were occulted. Specially, the defects of tunnel lining have been a serious problem in safety and stability many repair works for maintenance in tunnel have been carried out. Therefore, it is necessary to estimate the structural cracking for countermeasure in deformed tunnel and to investigate on the characteristics of lining system and the soundness of tunnel. In this study model tests for tunnel lining were carried out using test apparatus and centrifuge, In the direct loading test, the prototype was Kyungbu high-speed railway tunnel and the scale is 1/10, and lining models were made of concrete. Test conditions included load conditions such as direction, shape and type, lining conditions such as single and double lining, thickness, and reinforcement. In centrifuge model test, the prototype was Seoul subway tunnel and the scale is 1/100, and lining models were made of aluminum and hydrostone. Test conditions included tunnel defects such as thickness shortage. behind cavity and longitudinal cracks, reinforcement methods such as epoxy, grouting and carbon sheet. From these model tests , the characteristics of deformation and failure for tunnel lining were estimated, and the structural behaviors of deformed lining and the effects of repair and reinforcement for tunnel lining were researched.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.5
• /
• pp.1106-1114
• /
• 1993

A composite material is composed of a reinforcement and a matrix, which determine mechanical characteristics of the molded part. There is no doubt that the properties of a composite material depend not only on the characteristics of the matrix but also on the structure of glass fiber mat and a fiber type of reinforcement. Therefore it is very important to study the composites of reinforcement and the matrix, and to control the fiber type in the process of molding of composite materials. In this study, the specimen was made of a glass fiber mat of 6-7mm thickness by scattering it in the air after cutting the glass fiber mat with needle punching makes change according to the type of needle and the number of times of stretching. First the sheet was made by means of a hot-press after accumulating a matrix and a glass fiber according to each mat structure of glass fiber. It was heated the manufactured sheet with the dry oven and molded it a secondary high temperature compression by a 30 ton oilhydraulic press. A definition of a correlation coefficient is showed up during this period and find it out with the relation of the fiber-matrix separation and the fiber orientation. We studied effects of the glass fiber mat structures on the correlation coefficient.

• Journal of Korean Association for Spatial Structures
• /
• v.7 no.1 s.23
• /
• pp.79-85
• /
• 2007

Steel plate bonding method with epoxy is common applied to repair and strengthen RC structures, but Steel is apt to corrode quickly, hard to manufacture and heavy. To overcome these defects, it is carried out research on strengthening RC structures with FRP(Fibre Reinforced Polyrner/Plastic) FRP is generally used in the shape of Plate or Sheet, but it has weak point such as premature failure, difficult work. To cope with these problem, NSMR(Near Surface Mounted Reinforcement) which uses CFRP in the shape of Rod is proposed and carried out active research on strengthening effect of variables such as quantity, anchorage length and space of CFRP-Rod. Strengthening with CFRP-Rod is carried out under loading to some degree in fact, and so the amount of pre-loading is selected as variable in this research. The amount of pre-loading is chosen in proportion to nominal strength of non-strengthened specimen with CFRP-Rod.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3A
• /
• pp.349-356
• /
• 2008

Recently FRP (Fiber Reinforcement Polymer) is widely used for the strengthening of damaged RC beams. Although many tests were carried out to verify flexural capacity of RC beams strengthened with FRP sheet or plate, the behavior of strengthened RC beams has not yet clearly verified. To investigate the strengthening efficiency of the Near Surface Mounted Reinforcement (NSMR) technique experimentally and analytically, a total of 7 specimens have been tested. The experimental results revealed that specimens strengthened with NSMR improved the flexural capacity of RC beams. Also, while the NSMR specimens utilized CFRP reinforcement efficiently compared to the EBR (Externally Bonded Reinforcement) specimen, the NSMR specimens still have debonding failure between epoxy and concrete interface. This study has proposed the model to predict failure modes and failure loads. Good agreement was obtained between the predicted and the experimental results.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.393-398
• /
• 2002

This study shows the fatigue test results of experiment on the strengthened slabs, the probability analysis of the fatigue behavior is also presented. Static und fatigue tests were performed on bridge decks strengthened with fiber plastics(Carbon Fiber Sheet, Glass Fiber Sheet, Grid Type Carbon Fiber). In this study, to analyze the probabilistic distribution of the fatigue life, the Weibull distribution was adopted. The Weibull distribution coefficient is inferred from the S-N diagram and the number of repeated load. As the result analysis, as the stress level is higher, the fatigue limit of the strengthened bridge deck are similarly discovered but in the range of the fatigue limit, CG specimen that was strengthened with Grid Type Carbon was proved most effective of reinforcement.

• Journal of Welding and Joining
• /
• v.33 no.6
• /
• pp.36-41
• /
• 2015

In the automotive industry, TWB hot stamping process is broadly adapted to reduce weight of the car and improve fuel efficiency. However, the process faces a problem of weakened strength of the welded zone after hot stamping process, due to the fact that Al-Si elements of the coating layer penetrating the welded zone. In this study, filler wires with high percentages of carbon and manganese is adapted during laser welding process to secure the strength of the fusion zone. In addition, wire feeding speed and laser welding speed are optimized by sample test.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.691-696
• /
• 1999

This paper is aimed to investigate flexural rehabilitation effect o pre-loaded reinforced concrete beams strengthened by carbon fiber sheet. Main Test parameters are reinforcement ratio and the magnitude of pro-loading and seven test beams are analyzed rehabilitation effect by carbon fiber sheet, load-deflection, failure mode, stress of reinforcing bar by the magnitude of pre-loading. Test results show that internal force was showed pre-loaded specimens lower than no-loaded specimens during rehabilitation and changing stiffness was showed in the same was and failure mode showed brittle failure from all specimens.