철근 대체재로서 CFRP 보강근을 활용하기 위한 사례연구

고동우 한국복합신소재구조학회 2023 복합신소재구조학회논문집 Vol.14 No.5

Many countries worldwide are actively working toward reducing carbon emissions. To address the environmental impact of reinforced concrete (RC) structures, numerous researchers in the construction industry have been investigating the substitution of traditional steel reinforcement with fiber-reinforced polymer (FRP) reinforcement over the last few decades. While carbon-fiber-reinforced polymer (CFRP) reinforced concrete has found applications in offshore structures and road construction in regions such as North America, its use in building construction has been relatively understudied. Consequently, this study focuses on addressing this gap by selecting an example building, designing it as a reinforced concrete structure, and then replacing the steel rebar with CFRP rebar. The aim is to compare the quantity of steel rebar used in the conventional reinforced concrete structure with that of CFRP rebar.

Direct Shear Strength of Rebar-coupler Anchor Systems for Steel-plate Composite (SC) Walls

Efe G. Kurt,Amit H. Varma,Young M. Sohn 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.4

This paper focuses on the direct shear behavior of rebar-coupler anchor systems, and their use for anchorage of steel-plate composite (SC) walls to the concrete basemat of safety-related nuclear facilities. Large-scale rebar-coupler anchor specimens were tested under direct shear loading until failure. The results included the applied load-slip displacement responses of the specimens, the direct shear strength, and the observed failure mode. The American Concrete Institute (ACI) 349 code equation for calculating the direct shear strength of embedded anchors was compared with the direct shear strengths from the tests. The code equation underestimated the direct shear strength of the anchor system, because shear failure was assumed to occur in the rebars, whereas experimental observations indicated that shear fracture failure occurred in the couplers rather than the rebars. The design equation was updated to utilize the net shear area of the couplers instead of the rebars, after which the direct shear strengths from the tests could be calculated with reasonable accuracy. The experimental results were also used to propose an empirical model for the shear force vs. slip displacement response of rebar-coupler anchor systems.

Experimental investigation on UHPC beams reinforced with GFRP and steel rebars and comparison with prediction equations

Parvin, Yousef Abbasi,Shaghaghi, Taleb Moradi,Pourbaba, Masoud,Mirrezaei, Seyyed Saeed,Zandi, Yousef Techno-Press 2022 Advances in concrete construction Vol.14 No.1

In this article, the flexural and shear capacity of ultra-high-performance fiber-reinforced concrete beams (UHPFRC) using two kinds of rebars, including GFRP and steel rebars, are experimentally investigated. For this purpose, six UHPFRC beams (250 × 300 × 1650 mm) with three reinforcement ratios (ρ) of 0.64, 1.05, and 1.45 were constructed using 2% steel fibers by volume. Half of the specimens were made of UHPFRC reinforced with GFRP rebars, while the other half were reinforced with conventional steel rebars. All specimens were tested to failure in four-point bending. Both the load-deformation at mid-span and the failure pattern were studied. The results showed that utilizing GFRP bars increases the flexural strength of UHPFRC beams in comparison to those made of steel bars, but at the same time, it reduces the post-cracking strain hardening. Furthermore, by increasing the percentage of longitudinal bars, both the post-cracking strain hardening and load-bearing capacity increase. Comparing the experiment results with some of the available equations and provisions cited in the valid design codes reveals that some of the equations to predict the flexural strength of UHPFRC beams reinforced with conventional steel and GFRP bars are reasonably conservative, while Khalil and Tayfur model is un-conservative. This issue makes it essential to modify the presented equations in this research for predicting the flexural strength of UHPFRC beams using GFRP bars.

현장시험을 통한 고강도 강관을 이용한 쏘일네일의 거동특성 평가

박재만(Jeaman Park),박두희(Duhee Park),이종권(Jongkwon Lee),정경식(Kyoungsik Jung) 한국지반환경공학회 2021 한국지반환경공학회논문집 Vol.22 No.2

본 연구에서는 최근 강소재의 발전에 의해 고강도 강관의 제작이 실용화됨에 따라 고강도 강관 쏘일네일링 공법의 안정성 및 적용성에 대한 평가를 수행하였다. 쏘일네일링 공법에서 보강재로 사용되고 있는 이형철근을 동일직경의 고강도 강관으로 대체 할 때의 보강재의 거동특성과 보강력 증대효과를 규명하고 안정성을 확인하기 위하여 현장시험시공을 실시하였다. 인장시험결과 측정변형률 값이 이론식에서 산정된 변형률보다 작은 값을 보이므로 이형철근을 사용한 쏘일네일링 공법과 유사한 거동을 한다고 볼 수 있다. 변위측정 결과, 고강도 강관의 변위가 이형철근 보다 큰 값을 보이는 것은 강관 내부그라우팅 영향과 단면적 감소에 따른 영향인 것으로 판단된다. 쏘일네일링 공법에 고강도 강관을 사용하는 경우 부재성능 및 경량화를 통하여 안정성 및 시공성 향상에 따른 현장적용성이 양호한 것으로 판단된다. In this study, as the production of high-strength steel pipes due to the development of steel materials, the stability and applicability of the soil nailing method using high-strength steel pipes were evaluated. Rebars used as reinforcement in the soil nailing method are the same in order to determine the behavioral characteristics and the effect of increasing the reinforcement when replacing it with a high-strength steel pipe of a diameter, a field test were conducted to confirm the stability. As a result of the tensile test, the measured strain is smaller than the strain in the theoretical equation, so it can be seen that the behavior is similar to that of the soil nailing method using rebars. As a result of the displacement measurement, the displacement of the high-strength steel pipe is larger than that of the rebars is considered to be the effect of the internal grouting effect of the steel pipe and the decrease in the cross-sectional area. In the case of using high-strength steel pipes for the soil nailing method, it is judged that the field applicability is good by improving stability and workability through member performance and weight reduction.

Simplified Approach to Model Steel Rebar-Concrete Interface in Reinforced Concrete

Rashid Hameed,Alain Sellier,Anaclet Turatsinze,Frédéric Duprat 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.4

For correct description of cracking process in reinforced concrete structural elements, the simulation of the behaviour of steel rebarconcrete interface is always of primary importance. This paper proposes a simplified method to model the steel rebar-concrete interface in RC structures. The proposed method considers the introduction of massive elasto-plastic isotropic bond element as steel rebarconcrete interface. Stress-strain behaviour curve required for elasto-plastic isotropic material is obtained by performing conventional pull-out tests on concrete. For plain concrete matrix, an orthotropic damage model based on plasticity and damage theories was adopted for finite element modelling in Finite Element (FE) code CASTEM. In order to validate the proposed approach, a comprehensive experimental program was designed and carried out. Under this program, pure tension test on RC prisms and flexural test on RC beams were performed. Testing of proposed steel rebar-concrete interface bond model in numerical simulation of RC prism subjected to pure tension and RC beam in flexure, and comparison of numerical simulation results with experimental data is also discussed in this paper.

합성 콘크리트 공극 솔루션에서 철근에 히드라존 기반 헤테로고리 화합물의 흡착에 대한 실험 및 계산 통찰력

하산르가즈 ( Lgaz Hassane ),카르틱수비아 ( Karthick Subbiah ),이한승 ( Lee Han-seung ) 한국건축시공학회 2022 한국건축시공학회 학술발표대회 논문집 Vol.22 No.2

The corrosion inhibitive effect of a new hydrazone-based heterocyclic compound for steel in simulated concrete pore solution with 3.5 wt.% sodium chloride was investigated by experimental and computational techniques. Electrochemical studies, up to 30 days of immersion, and surface analysis (X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscope (SEM)) were performed to assess the corrosion protection abilities of investigated compound for steel rebar. Results showed that adding the organic compound to the chloride contaminated concrete pore solution decreased the corrosion rate of the steel rebar thanks to the effective adsorption of inhibitor molecules. After 30 days of immersion of steel rebar in inhibited chloride contaminated synthetic concrete pore solution, the inhibition efficiency exceeded 80% at low concentration of 1 mmol/L. Computational studies by Density Functional based Tight Binding (DFTB) method revealed the formation of covalent bonds between the hydrazone molecule and the iron surface.

철근 배근 방법에 의한 철근콘크리트의 전자파 차폐특성 평가

최진석(Choi, JinSeok),원천봉(Yuan, TianFeng),홍세희(Hong, SeHee),윤영수(Yoon, YoungSoo) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.5

본 연구에서는 콘크리트의 두께와 철근 보강에 따른 철근콘크리트의 전자파 차폐특성에 관한 실험을 수행하였다. 또한, 섬유보강 콘크리트의 강섬유 혼입률 및 철근 간격에 따른 전자파 차폐특성을 평가하였다. 콘크리트는 두께의 증가에 따라 높은 주파수 대역에서 전자파 차폐에 큰 효과를 나타냈으며 철근은 직경의 증가, 철근 간격의 감소 및 보강 층의 증가에 따라 낮은 주파수 대역에서 전자파 차폐에 큰 효과를 나타냈다. 강섬유의 혼입률이 증가할수록 차폐율이 증가하였으며 강섬유를 1.5% 혼입한 변수에서 철근 간격의 감소로 인한 차폐율 증가를 나타냈다. In this study, experimental tests were performed to determine the electromagnetic shielding characteristics of reinforced concrete based on the thickness of concrete and rebar. In addition, the electromagnetic shielding characteristics based on the steel-fiber volume ratio and rebar spacing of fiber-reinforced concrete were evaluated. Concrete showed significant Shielding Effectiveness (SE) in a high-frequency band with increasing thickness, but the rebar exhibited significant SE in the low-frequency band with increasing diameter, decreasing rebar spacing, and increasing layer. The SE increased with the steel fiber volume ratio, and it also increased owing to the decrease in the rebar spacing for 1.5 vol.% steel fibers.

연속 섬유강화 복합재료 리바 개발에 관한 연구

한길영,이동기,김성용 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

This paper describes the need for a ductile Fiber Reinforced Plastic(FRP) reinforcement for concrete structures. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudo-ductility characteristic can be generated in FRP rebar. Ductile hybrid FRP bars were successfully fabricated at 4mm and 10mm nominal diameters using an hand lay up method. Tensile specimens from these bars were tested and compared with behavior of FRP rebar and steel bar. The summarized results are as follows : The tensile strength of CFRP, KFRP and GFRP rebar with nominal diameter ψ4mm, respectively, showed 91.7kg/mm^2, 66.5kg/mm^2, 53.6kg/mm^2. The tensile strength of CFRP, KFRP, GFRP rebar with nominal diameter ψ10mm by the hand lay up method, respectively, showed 125.4kg/mm^2, 54.1kg/mm^2, 46kg/mm^2.

Simplified approach on modeling of embedded reinforcements in flexural concrete members

Hosseini, Seyed Muoud,Ghomian, Majid,BaniAsad, Elham,Dehestani, Mehdi Techno-Press 2021 Advances in concrete construction Vol.12 No.3

Several factors need to be considered in modeling of reinforced concrete beams. Bond-slip is one of the most important factors that play a key role in the behavior of reinforced concrete structures, under static and dynamic loads. A comparison between the results of experimental tests and numerical models show that considering a complete bond (perfect with no slip) instead of real bond-slip phenomenon, in numerical finite element models leads to higher estimations for the stiffness. In this study, the effects of the bond-slip phenomenon on the behavior of the reinforced concrete beams are considered. It is shown that the influence of bond-slip behavior between steel and concrete depends on the compressive strength of concrete, the concrete cover, stirrups and rebar diameter. Subsequently, a method is proposed to consider the effects of the interfacial behavior between concrete and rebar while a complete bond assumption remains and the rebar is introduced as embedded element in concrete. The bond-slip effect is considered by adding an equivalent strain of bond to the strain of steel rebar and then modifying the terms of the modulus of elasticity of steel. Validation model and parametric analyses are conducted to consider the effects of bond-slip properties and other parameters affecting the behavior of reinforced concrete beams.

Effect of Microstructures on the Corrosion Behavior of Reinforcing Bars (Rebar) Embedded in Concrete

Prvan Kumar Katiyar,Prasanna Kumar Behera,Sudhir Misra,K. Mondal 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5

This work aims at understanding the effect of microstructures (coarse, medium and fine ferrite–pearlite, martensite andtempered martensite) of a reinforced (rebar) steel developed by various heat-treatments (furnace cooling, air-cooling, forceair-cooling, quenching, and tempering, respectively) on its corrosion behavior in freely aerated 3.5% NaCl + 3.5% FeCl3solution. The impressed current technique was used for forcing corrosion of the rebar, which was embedded in concretecoupon, so that correlation could be drawn between microstructure and corrosion behavior in short duration. Corrosionsusceptibility increased from force air-cooled–quenched–air cooled–furnace cooled–tempered steels. The crack formationin the concrete was directly related to the rust composition and thickness, presence of crack in the rust, alpha/gamma* ratioand critical corrosion amount.