• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.154-159
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• 1996

In this thesis, a series of loading tests are conducted in order to investigate the fracture safety of GFRP(Glass Fiber Reinforced Plastics) pipes under fatigue load which are widely used in the developed countries becauses of their natural of anticorrosion and lightweight etc. . Fatigue test is performed by changing number of laminates and loading cycles to examine the flexural strains, the ductility and the fatigue strength for two million repeated loading cycles. From the fatigue test results, it was found that the larger the laminates of GFRP pipes is, the larger the stiffness of GFRP pipes under the fatigue load increases. This phenomenon is true until the fatigue failure. According to the S-N curve drawn by the regression analysis on the fatigue test results, the fatigue strength of percent of the static ultimate strength increases by increasing the laminates of GFRP pipes. The fatigue strength with two million repeated leading cycles in GFRP pipes with the laminates of GFRP pipes varing 15, 25, 35 shows about 75%, 80%, 84% on the static ultimate strength, respectively.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.1-8
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• 2012

Recently, underground pipes are utilized in various fields of applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. Most of pipes are installed for long-term purposes and they should be safely installed in consideration of installation conditions because there are unexpected various terrestrial loading conditions. In this paper, we present the result of investigation pertaining to the structural behavior of glass fiber reinforced thermosetting polymer plastic (GFRP) flexible pipes buried underground. The mechanical properties of the GFRP flexible pipes produced in the domestic manufacturer are determined and the results are reported in this paper. In addition, ring deflection is measured by the field tests and the finite element analysis (FEA) is also conducted to simulate the structural behavior of GFRP pipes buried underground. From the field test results, we predicted long-term, up to 50 years, ring deflection of GFRP pipes buried underground based on the method suggested by the existing literature. It was found that the GFRP flexible pipe to be used for cooling water intake system in the nuclear power plant is appropriate because 5% ring deflection limitation for 50 years could be satisfied.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.219-226
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• 1994

In the comparison result of residual strain calculated from the load-strain curve under the repeated loading cycles, it was found that the larger the laminates is, the larger the stiffness of GFRP pipes under fatigue load is. This phenomenon is true until the fatigue failure. According to the S-N curves drawn by the regression analysis on the fatigue test results, the fatigue strength for percentage of the static ultimate strength increases by increasing the laminates of GFRP pipes. The fatigue strength for 2, 000, 000 repeated loading cycles In GFRP pipes with the laminates varing 15, 25, 35 shows 75.2%, 79.5%, 84.2% on the static ultimate strength, respectively.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.1
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• pp.27-33
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• 2010

Static analyses and buckling analyses were carried out for buried GFRP pipes by using finite element method. Vehicle loads, vertical and lateral soil pressures were considered as external loads, and supplying water pressure was considered as an internal load. Nine types of the factory-manufactured GFRP pipes were analyzed. Their maximum stresses and displacements were compared with the limit displacements and ultimate stress. Additionally, stress analysis on an enhanced flange, which was designed to reduce stress concentration, was performed. A cantilever analysis was carried out to know the maximum stress on the neck of the flange, which is the critical part. And a static analysis was carried for the buried flange. The test results showed that GFRP pipes were safe and stable against the external loads. And they showed that the enhanced flange decreased about 35% of the stress concentration.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.2 s.13
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• pp.35-45
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• 2004

Recently, the composite material becomes more popular and its usage is kept expanding from aerospace to civil structures such as bridge decks and irrigation and drainage pipes. The major cause for the popularity can be found in its high strength, light, and excellent anticorrosive properties. Nevertheless the methods to accurately predict and analyze its structural behavior are extremely limited. This has been the major reason circumventing more prevalent use of the composite materials in civil structures. This study is a pre-study to develop the analyzing models for accurate prediction of the composite material structures. Thus, various tests were performed for GFRP pipes to estimate material characteristics of GFRP in this study. And stress-strain relation of GFRP was suggested as a bilinear relation.

• Journal of the Korean Geosynthetics Society
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• v.13 no.1
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• pp.33-40
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• 2014

In general, pipes buried underground can be classified into either rigid or flexible pipe. Glass fiber reinforced thermosetting polymer plastic (GFRP) pipe can be considered as one of typical flexible pipes for which the soil-pipe structure interaction must be taked into account in the design. In this paper, we present the result of an investigation pertaining to the short-term and long-term behavior of buried GFRP pipe. The mechanical properties of the GFRP pipe produced in the domestic manufacturer are determined and the results are reported in this paper. In addition, Ring deflection is measured by the field tests and the finite element analysis. Also, the extrapolation using these techniques typically extends the trend from data gathered over a period of approximately 5,232 hours, to a prediction of the property at 50 years, which is the typical maximum extrapolation time. Therefore, it was investigated that the long-term ring deflection of GFRP pipe estimated by methods for Monod-type.

• Composites Research
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• v.22 no.3
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• pp.1-8
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• 2009

In this paper, we present the results of experimental and analytical investigations on the structural behavior of GFRP pipes used in the water supply pipeline system. Cross-section of the pipe is consisted with two GFRP tubes and polymer mortar between the tubes. Due to the advantages such as light-weight, corrosion resistance, smooth surface, flexibility, etc., use of GFRP pipe in the water supply pipeline system is ever increasing trend. Therefore, more optimized structural design methodology should be developed. In the investigation, we conducted theoretical and analytical studies on the load versus radial deformation characteristics of GFRP pipes. In addition, ring stiffness test is also performed. Test results are compared with theoretical and analytical results and it was found that the results are agreed well within 5% of radial deformation. Finally, it was also found that the GFRP pipes used in the water supply pipeline system are strong enough to satisfy the industrial requirements.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1050-1059
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• 2010

The GFRP(Glass-Fiber Reinforced Plastic) Pipe is designed to behave safely against the external forces and to secure stability of deformation and settlements in pipe, Since it is laid under the ground. In this syudy, the evaluation for stability was carried out by performing the preliminary numerical analysis to decide the sclae effect in case of indoor model test. As a result of, strain of laying pipes is preponderantly reviewed. Numerical analysis is conducted to evaluate on the field application through the comparison concerning relations between deformation and differential settlement in the GFRP and hume pipes.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.121-126
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• 1994

In this thesis, a series of loading tests are conducted in order to investigate the fracture safety as structural materials of GFRP(Glass Fiber Reinforced Plastics) which we wifely used in the developed countries becauses of their natural of anticorrosion and lightweight etc.. In the fracture test, the mid-span displacement, the strain and the yield load of the GFRP pipes are measured for different number of laminates, and fracture energy is estimated. From this study, it is known that GFRP pipe could be used as structural materials in underground buried pipes if their ductility and strength are increased by controlling number of laminates. Furthermore, because of their merit of lightweight, they can contribute greatly to reduction of construe-tlon cost when they are employed.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.187-194
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• 1993

본 논문에서는 유리섬유의 적층수, 유리섬유의 배향각도에 대한 유리섬유 강화 플라스틱(Glass Fiber Reinforced Plastics ; GFRP)의 인장거동 변화를 고찰하고, 이들의 상관관계를 규명하기 위하여 일련의 GFRP 시험체에 대하여 인장실험을 수행하였다. 시험체는 폭12.5mm, 길이 60mm크기로 일정하게 제작하였으며, 시험체에 대하여 인장실험을 수행하였다. 시험체 제작시 유리섬유로 적층수는 14, 22, 30층, 유리섬유의 배향각도는 0$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$로 하였다. 인장실험시 각 시험체의 파괴양상, 극한하중 및 하중변화에 대한 인장변형율을 조사하였고, 이들 결과를 토대로 유리섬유의 적층수와 배향각도에 따른 GFRP의 극한하중, 응력-변형율 선도 및 탄성계수 등을 비교 분석하였다. 한편 본 논문에서는 유리섬유의 적층수, 직경 변화에 따른 GFRP관의 파괴거동을 고찰하기 위하여 4점 재하법에 의한 GFRP관의 휨파괴실험을 수행하였다. 실험에 사용된 시험체는 길이 1200mm로 하였으며, 유리섬유의 적층수를 30, 35, 40층, 관의 직경을 50, 100, 150mm로 하였다. 파괴실험시 각 시험체의 하중변화에 대한 휨 변형율, 중앙점 처짐량 및 항복하중을 측정하였고, 이들 결과를 토대로 유리섬유으 적층수와 관의 직경에 따라 GFRP관의 항복하중 및 파괴에너지를 비교 분석 하였으며, 항복시 파괴에너지를 추정할 수 있는 제안식을 유도하였다.