• 폴리머
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• 제38권2호
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• pp.171-179
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• 2014

우수한 성능을 지닌 대형 구조의 섬유강화 고분자(FRP) 복합재료 제품을 제조하기 위해 저온 경화형 프리프레그 개발이 활발히 진행되고 있다. 본 연구에서는 저온 경화형 프리프레그 제조에 적합한 매트릭스 수지를 확보하기 위하여 에폭시 수지, 경화제, 경화 촉진제로 구성된 저온 경화형 에폭시 수지 조성물의 경화거동 및 화학유변학을 고찰하였다. 경화반응 특성은 시차주사열량분석법과 유변물성측정법을 활용하여 승온 및 등온 조건에서 분석하였다. 연구 결과 매트릭스 수지로 제안된 저온 경화형 에폭시 수지 조성물은 $80^{\circ}C$에서 3시간에 경화시킬 수 있었고, 80과 $90^{\circ}C$에서의 젤화 시간은 각각 120분과 20분인 것으로 나타났다. 저온 경화형 수지를 경화시킨 수지 경화물의 열적, 기계적 물성은 고온 경화형 수지 경화물의 물성과 거의 동등하였다.

• Structural Engineering and Mechanics
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• 제47권5호
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• pp.623-641
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• 2013

The fiber-reinforced polymer (FRP) composite panel, with the benefits of light weight, high strength, good corrosion resistance, and long-term durability, has been considered as one of the prosperous alternatives for structural retrofits and replacements. Although with these advantages, a further application of FRPs in bridge engineering may be restricted, and that is partly due to some unsatisfied thermal performance observed in recent studies. In this regard, Kansas Department of Transportation (DOT) conducted a field monitoring program on a bridge with glass FRP (GFRP) honeycomb hollow section sandwich panels. The temperatures of the panel surfaces and ambient air were measured from December 2002 to July 2004. In this paper, the temperature distributing behaviors of the panels are firstly demonstrated and discussed based on the field measurements. Then, a numerical modeling procedure of temperature fields is developed and verified. This model is capable of predicting the temperature distributions with the local environmental conditions and material's thermal properties. Finally, a parametric study is employed to examine the sensitivities of several temperature influencing factors, including the hollow section configurations, environmental conditions, and material properties.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.535-546
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• 2018

The objective of this study is to understand the behaviour of hollow core slabs strengthened with FRP and hybrid techniques through numerical and analytical studies. Different strengthening techniques considered in this study are (i) External Bonding (EB) of Carbon Fiber Reinforced Polymer (CFRP) laminates, (ii) Near Surface Mounting (NSM) of CFRP laminates, (iii) Bonded Overlay (BO) using concrete layer, and (iv) hybrid strengthening which is a combination of bonded overlay and NSM or EB. In the numerical studies, three-dimensional Finite Element (FE) models of hollow core slabs were developed considering material and geometrical nonlinearities, and a phased nonlinear analysis was carried out. The analytical calculations were carried out using Response-2000 program which is based on Modified Compression Field Theory (MCFT). Both the numerical and analytical models predicted the behaviour in agreement with experimental results. Parametric studies indicated that increase in the bonded overlay thickness increases the peak load capacity without reducing the displacement ductility. The increase in FRP strengthening ratio increased the capacity but reduced the displacement ductility. The hybrid strengthening technique was found to increase the capacity of the hollow core slabs by more than 100% without compromise in ductility when compared to their individual strengthening schemes.

• Structural Monitoring and Maintenance
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• 제4권1호
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• pp.69-84
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• 2017

Delamination is the most common failure mode in layered composite materials. The author have found that the electrical potential change (EPC) technique using response surfaces method is very effective in assessment delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). In the present study, the effect of the electrodes number on the method is investigated using FEM analyses for delamination location/size detection by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Three cases of electrodes number are analyzed here are eight, twelve and sixteen electrodes, afterwards, the delamination is introduced into between the three layers [$0^{\circ}/90^{\circ}/0^{\circ}$]s laminates pipe, split into eight, twelve and sixteen scenarios for cases of eight, twelve and sixteen electrodes respectively. Response surfaces are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured EPC of all segments between electrodes. As a result, it was revealed that the estimation performances of delamination location/size depends on the electrodes number. For ECS, the high number of electrodes is required to obtain high estimation performances of delamination location/size. The illustrated results are in excellent agreement with solutions available in the literature, thus validating the accuracy and reliability of the proposed technique.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.906-913
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• 2006

The failure mechanism of a hollow bridge deck which is made of glass fiber reinforced polymer(GFRP) is investigated using both experiments and analysis. While the load-displacement behavior of the deck in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. In order to imporve the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and investigated experimentally the static behavior of the orthotropic bridge deck which is made from GFRP and polyurethane foam. It is found that although the elastic modulus of the foam compared to that of the GFRP is about the order of $10^{-3}$, the structural behaviors in the weak axis such as nominal strength, stiffness, etc. are greatly improved. Owing to the low mass density of the foam used in this study, the bridge deck is still light enough with the improved structural properties.

• Geomechanics and Engineering
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• 제10권3호
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• pp.315-324
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• 2016

Frictional forces between soil and structural elements are of vital importance for the foundation engineering. Although numerous studies were performed about the soil-structure interaction in recent years, the approximate relations proposed in the first half of the 20th century are still used to determine the frictional forces. Throughout history, wood was often used as friction piles. Steel has started to be used in the last century. Today, alternatively these materials, FRP (fiber-reinforced polymer) piles are used extensively due to they can serve for long years under harsh environmental conditions. In this study, various ratios of low plasticity clays (CL) were added to the sand soil and compacted to standard Proctor density. Thus, soils with various internal friction angles (${\phi}$) were obtained. The skin friction angles (${\delta}$) of these soils with FRP, which is a composite material, steel (st37) and wood (pine) were determined by performing interface shear tests (IST). Based on the data obtained from the test results, a chart was proposed, which engineers can use in pile design. By means of this chart, the skin friction angles of the soils, of which only the internal friction angles are known, with FRP, steel and wood materials can be determined easily.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.365-368
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• 2006

RBSN Method, Rigid-Body-Spring Network Method, is a structural analysis method that overcomes the problems faced in FEM analysis of concrete or crack forming structures. In RBSN, irregular lattices are used to model structural components consisting of bulk material, curvilinear reinforcements, and their interfaces. Because reinforcements and their interfaces in the bulk material are freely positioned, meshing is irrespective of the geometry of the representing bulk material. In this paper, RBSN method of 3D is applied in simulating the pull-out test of FRP (Fiber Reinforced Polymer) embedded in concrete. The comparison of analysis results to experimental results shows that RBSN method simulates the shear-slip behavior very precisely. From the analysis results, 3D RBSN method is proven to be an effective and accurate analysis method for concrete structural analysis. Also, the results show that RBSN method can be a potential analysis method for concrete structures that can replace the current FEM analysis.

• 한국농공학회논문집
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• 제50권5호
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• pp.51-60
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• 2008

This study is to relate the bond characteristics of CFRP rebar in high strength concrete incorporated with silica fume(SF) and metakaolin(MK). An direct bond test were performed to evaluate the effect of SF and MK on bond properties of high-strength concrete and CFRP rebar. The high strength concrete mix included four SF and MK mixes with 0%, 5%, 10% and 15%. Results of bond performance experiment in relation to pullout vs slip behavior of FRP rebar and high strength showed better performance of SF than MK. Also, the results showed the improved bond strength as replacement ratio of SF and MK increased. The relative bond strength in which $1.3{\sim}3.2$ of estimated values were obtained.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.735-742
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• 2017

Steel cables as the most important components are widely used in the certain types of structures such as cable-supported bridges, but the long-span structures may result in an increase in fatigue under high stress and corrosion of steel cables. The traditional steel cable is becoming a more evident hindrance. Fiber Reinforced Polymer (FRP) cables with lightweight, high-strength are widely used in civil engineering, but there is little research in vibrational characteristics of FRP cables, especially on the damping characteristic. This article studied the two methods to evaluate dynamical damping characteristic of basalt FRP(BFRP) and glass FRP(GFRP) cables. First, the vibration tests of the B/G FRP cables with different diameter and different cable force were executed. Second, the cables forces were calculated using dynamic strain, static strain and dynamic acceleration respectively, which were further compared with the measured force. Third, experimental modal damping of each cables was calculated by the half power point method, and was compared with the calculation by Rayleigh damping theory and energy dissipation damping theory. The results indicate that (1) The experimental damping of FRP cables decreases with the increase of cable force, and the trend of experimental damping changes is roughly similar with the theoretical damping. (2) The distribution of modal damping calculated by Rayleigh damping theory is closer to the experimental results, and the damping performance of GFRP cables is better than BFRP cables.

• 대한토목학회논문집
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• 제26권6A호
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• pp.943-953
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• 2006

본 연구에서는 섬유강화 플라스틱(FRP) 소재로 제작된 사각형 중공 교량 바닥판의 약축방향 거동을 보완하기 위해서 바닥판의 중공 내부를 구조용 폼(foam)으로 충전하였다. 충전폼의 유무와 폼의 강도에 따른 약축방향 정적거동 특성을 실험적으로 분석하여 충전폼의 역할을 검토하였다. FRP에 비하여 탄성계수가 현저히 낮은 구조용 폼으로 바닥판 내부를 충전하여 도 본래의 경량성을 유지하면서 공칭강도, 강성 등의 횡방향 구조성능이 획기적으로 개선되었다. 웨브의 개수에 따른 파괴거동을 비교하여 내부충전 FRP 바닥판에서 웨브의 역할을 파악하였다. 웨브가 내부충전 FRP 바닥판의 약축방향 강도에 미치는 영향은 미미하였으나, 폼 내부에서 발생한 균열의 전파를 차단함으로써 파괴모드의 취성을 경감시켰다.