• Title/Summary/Keyword: FRP concrete

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Nonlinear Flexural Modeling of Prestressed Concrete Beams with Composite Materials (복합소재 프리스트레스트 콘크리트보의 비선형 휨 모델링)

  • ;;Naaman, Antoine
    • Magazine of the Korea Concrete Institute
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    • v.10 no.6
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    • pp.269-280
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    • 1998
  • Recently, application of composite materials such as fiber reinforced concretes(FRCs) and fiber reinforced plastics(FRPs) in conjunction with conventional structural components has become one of the main research areas. A proper use of advanced composite materials requires understanding their resistance mechanism and failure mode when they are applied to structures or their components. Particular considerations are given in this research to develop an analytical model which can predict the nonlinear flexural responses of bonded and unbonded prestressed concrete beams possibly having layers of different cementitious composite matrices in a section and/or FRP tendons. The block concept is used, which can be regarded as an intermediate modeling method between the couple method with one block and the layered method with multiply sliced layers in a section. In order to find a particular deflection point of a beam under load, solutions to the 2N-variables are found numerically by using approximate N-force equilibrium equations and N-moment equilibirum equations. The model is shown to successfully predict the flexual behavior of variously reinforced bonded and unbonded prestressed concrete beams. The model is also successful in simulating a gradually increasing load after sudden drop inload resistance due to fracture of one or more FRP tendons. This feature is useful in tracing the overall load-deflection response of a beam prestressed with brittle FRP tendons.

Pseudo-Ductile Hybrid FRP Sheet for Strengthening Reinforced Concrete Beams (유사연성 하이브리드 FRP 시트를 이용한 RC 보의 휨 보강)

  • Ha, Sang-Su;Choi, Dong-Uk;Lee, Chin-Yong;Kim, Kil-Hee
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.239-247
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    • 2008
  • Use of both carbon fiber (CF) and glass fiber (GF) at the same time to strengthen existing flexural members was exploited. Using a proper volumetric GF / CF ratio, the CF can rupture first followed by subsequent rupture of GF at higher stress and strain showing a pseudo-ductile behavior. A theoretical study indicated that the ratio is 4.62 : 1 and higher where the pseudoductile effect can be shown. Flexural tests of plain concrete beams strengthened using fibers were first carried out. Hybrid FRP sheet using 8.8 : 1 ratio was then fabricated and the sheet was used to strengthen reinforced concrete beams. The RC beams strengthened using 1-ply and 2-ply hybrid sheets both revealed increased strength over a non-strengthened beam and ductile flexural behavior. A comparable beam strengthened using CF also showed increased strength but with limited ductility.

Evaluating Impact Resistance of Externally Strengthened Steel Fiber Reinforced Concrete Slab with Fiber Reinforced Polymers (섬유 보강재로 외부 보강된 강섬유 보강 콘크리트 슬래브의 충격저항성능 평가)

  • Yoo, Doo-Yeol;Min, Kyung-Hwan;Lee, Jin-Young;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
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    • v.24 no.3
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    • pp.293-303
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    • 2012
  • Recently, as construction technology improved, concrete structures not only became larger, taller and longer but were able to perform various functions. However, if extreme loads such as impact, blast, and fire are applied to those structures, it would cause severe property damages and human casualties. Especially, the structural responses from extreme loading are totally different than that from quasi-static loading, because large pressure is applied to structures from mass acceleration effect of impact and blast loads. Therefore, the strain rate effect and damage levels should be considered when concrete structure is designed. In this study, the low velocity impact loading test of steel fiber reinforced concrete (SFRC) slabs including 0%~1.5% (by volume) of steel fibers, and strengthened with two types of FRP sheets was performed to develop an impact resistant structural member. From the test results, the maximum impact load, dissipated energy and the number of drop to failure increased, whereas the maximum displacement and support rotation were reduced by strengthening SFRC slab with FRP sheets in tensile zone. The test results showed that the impact resistance of concrete slab can be substantially improved by externally strengthening using FRP sheets. This result can be used in designing of primary facilities exposed to such extreme loads. The dynamic responses of SFRC slab strengthened with FRP sheets under low velocity impact load were also analyzed using LS-DYNA, a finite element analysis program with an explicit time integration scheme. The comparison of test and analytical results showed that they were within 5% of error with respect to maximum displacements.

Strengthening Effects of RC Column using Fiber Reinforced Polymer (섬유보강재를 이용한 RC 기둥의 보강 효과)

  • Lee, Hyun-Ho;Kim, Jin-Ho;Rho, Kwamg-Geun
    • Journal of the Korea Concrete Institute
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    • v.24 no.4
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    • pp.473-480
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    • 2012
  • In order to develop an effecive seismic strengthening metghod for existing concrete structure, structural tests of aramid FRP reinforced RC columns are performed. The test variables were strengthening methods of aramid sheet and strip. The test results were evaluated by comparing strength and energy dissipation capacities of non-reinforced and reinforced specimens. The test result comparison showed that aramid sheet reinforcement on RC column was evaluated as the most efficient way to increase strength and energy dissipation capacity.

Seismic Ductility Assessment of RC Bridge Piers With Minor Earthquake Damage By the Quasi Static Test (유사정적실험에 의한 지진이력 철근콘크리트 교각의 내진 연성도 평가)

  • 이은희;정영수;박창규;김영섭
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.505-511
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    • 2003
  • Experimental investigation was conducted into the flexure/shear-critical behavior of earthquake-damaged reinforced concrete columns with lap splicing of longitudinal reinforcement in the plastic hinge region. Six test specimens in the aspect ratio of 2,5 were made with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes of which magnitude could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P=$0.1f_{ck}A_g. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that RC bridge piers with lap-spliced longitudinal steels in the plastic hinge region appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility, and strain energy ductility.

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Finite Element Analyses of Seismically Vulnerable Reinforced Concrete Building Frame Retrofitted Using FRP Column Jacketing System (FRP 기둥 재킷 시스템이 보강된 지진 취약 철근콘크리트 건축물의 유한요소해석)

  • Shin, Jiuk;Lee, Sang-Youl;Ji, Dong-Hyun
    • Journal of Korean Association for Spatial Structures
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    • v.21 no.2
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    • pp.57-66
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    • 2021
  • This study develops finite element models for seismically-deficient reinforced concrete building frame retrofitted using fiber-reinforced polymer jacketing system and validates the finite element models with full-scale dynamic test for as-built and retrofitted conditions. The bond-slip effects measured from a past experimental study were modeled using one-dimensional slide line model, and the bond-slip models were implemented to the finite element models. The finite element model can predict story displacement and inter-story drift ratio with slight simulation variation compared to the measured responses from the full-scale dynamic tests.

Effects of sulphuric acid on mechanical and durability properties of ECC confined by FRP fabrics

  • Gulsan, Mehmet Eren;Mohammedameen, Alaa;Sahmaran, Mustafa;Nis, Anil;Alzeebaree, Radhwan;Cevik, Abdulkadir
    • Advances in concrete construction
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    • v.6 no.2
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    • pp.199-220
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    • 2018
  • In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.

FBG Optical Fiber Sensors Embedded in Fiber Reinforced Polymer Composite Reinforcing Bars (철근대용 FRP 복합재에 삽입된 FBG 센서의 변형률에 관한 연구)

  • Kim, Myong-Se;Cho, Hyung-Sik;Cho, Sung-Kyu;Yoon, Jae-Jun;Baek, Hyun-Deok;Kim, Ki-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.124-133
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    • 2007
  • In our research, we focused on the FBG sensor system which is one of the fiber optic sensor system. The FBG sensor system is used for structural measurements. The problem of FBG sensor is very thin and weak. The methods that can protect FBG optical fiber sensor front outside forces such as the impacts are investigated. The FBG sensor embedded in the fiber reinforced composites which can replace the reinforcing steel bars in concretes can be applied to the concrete structures by embedding to the composite materials. The progresses in tensile strength of FBG sensor embedded in the reinforcing FRP bars in the concrete structures compare to plain FBGs were observed and the good long term durability is expected.

Enhancing the Blast Resistance of Structures Using HPFRCC, Segmented Composites, and FRP Composites (HPFRCC, 분절 복합체 및 FRP를 활용한 구조물의 내폭 성능 향상)

  • Yoon, Young-Soo;Yang, Jun-Mo;Min, Kyung-Hwan;Shin, Hyun-Oh
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.745-748
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    • 2008
  • The past structures were just required bearing capacity to service load, serviceability, and resistance to corrosion. However this point of view has changed after 9.11 terrorism, capacities which can bear impact loading by explosion, and heat by fire happening at the same time, become to be important as a basic condition. The blast resistance capacity of structures is very important part against all over the world is intimidated by terrorism everyday in current point of time. The target of this research is a development of segmented composites and layered structures with high blast resistance using cementitious composites, concrete and FRP composites, which has high tensile strength and ductility, to apply in not only existing facilities but also new ones. Through the improvement of blast resistance, casualties and economic loss can be minimized, and it is possible to diminish the structure collapse and delay the time of structure collapse by thermal effect, impact loading, dynamic loading and high strain.

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Comparison of the Fatigue Behaviors of FRP Bridge Decks and Reinforced Concrete Conventional Decks Under Extreme Environmental Conditions

  • Kwon, Soon-Chul;Piyush K. Dutta;Kim, Yun-Hae;Anido, Roberto-Lopez
    • Journal of Mechanical Science and Technology
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    • v.17 no.1
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    • pp.1-10
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    • 2003
  • This paper summarizes the results of the fatigue test of four composite bridge decks in extreme temperatures (-30$^{\circ}C$ and 50$^{\circ}C$ ). The work was performed as part of a research program to evaluate and install multiple FRP bridge deck systems in Dayton, Ohio. A two-span continuous concrete deck was also built on three steel girders for the benchmark tests. Simulated wheel loads were applied simultaneously at two points by two servo-controlled hydraulic actuators specially designed and fabricated to perform under extreme temperatures. Each deck was initially subjected to one million wheel load cycles at low temperature and another one million cycles at high temperature. The results presented in this paper correspond to the fatigue response of each deck for four million load cycles at low temperature and another four million cycles at high temperature. Thus, the deck was subjected to a total of ten million cycles. Quasi-static load-deflection and load-strain responses were determined at predetermined fatigue cycle levels. Except for the progressive reduction in stiffness, no significant distress was observed in any of the composite deck prototypes during ten million load cycles. The effects of extreme temperatures and accumulated load cycles on the load-deflection and load-strain response of FRP composite and FRP-concrete hybrid bridge decks are discussed based on the experimental results.