• Computers and Concrete
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• 제20권4호
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• pp.439-448
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• 2017

Reinforced concrete (RC) infrastructures often require strengthening due to error in design, degradation of materials properties after prolong utilization and increases load carrying capacity persuaded by new use of the structures. For this purpose, a newly proposed Side Near Surface Mounted (SNSM) composite technique was used for flexural strengthening of RC beam specimens. Analytical and non-linear finite element modeling (FEM) using ABAQUS were performed to predict the flexural performance of RC specimens strengthened with S-NSM using steel bars as a strengthening reinforcement. RC beams with various SNSM reinforcement ratios were tested for flexural performance using four-point bending under monotonic loading condition. Results showed significantly increase the yield and ultimate strengths up to 140% and 144% respectively and improved failure modes. The flexural response, such as failure load, mode of failure, yield load, ultimate load, deflection, strain, cracks characteristic and ductility of the beams were compared with those predicted results. The strengthened RC beam specimens showed good agreement of predicted flexural behavior with the experimental outcomes.

• Structural Engineering and Mechanics
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• 제88권1호
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• pp.67-81
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• 2023

The reinforced concrete (RC) structures might need strengthening or upgradation due to adverse environmental conditions, design defects, modification requirements, and to prolong the expected lifespan. The RC beams have been efficiently strengthened using the near surface mounted (NSM) approach over the externally bonded reinforcing (EBR) system. In this study, the performance of RC beam elements strengthened with NSM-steel rebars was investigated using an experimental program and nonlinear finite element modeling (FEM). Nine medium-sized, rectangular cross-section RC beams total in number made up for the experimental evaluation. The beams strengthened with varying percentages of NSM reinforcement, and the number of grooves was assessed in four-point bending experiments up to failure. Based on the experimental evaluation, the load-displacement response, crack features, and failure modes of the strengthened beams were recorded and considered. According to the experimental findings, NSM steel greatly improved the flexural strength (up to about 84%) and stiffness of RC beams. The flexural response of the tested beams was simulated using a 3D non-linear finite element (FE) model. The findings of the experiments and the numerical analysis showed good agreement. The effect of the NSM groove and reinforcement on the structural response was then assessed parametrically.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.179-195
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• 2023

The performance of reinforced concrete (RC) beam specimens strengthened using a newly proposed Side Near Surface Mounted (S-NSM) technology was investigated experimentally in this work. In addition, analytical and nonlinear finite element (FE) modeling was exploited to forecast the performance of RC members reinforced with S-NSM utilizing steel bars. Five (one control and four strengthened) RC beams were evaluated for flexural performance under static loading conditions employing four-point bending loads. Experimental variables comprise different S-NSM reinforcement ratios. The constitutive models were applied for simulating the non-linear material characteristics of used concrete, major, and strengthening reinforcements. The failure load and mode, yield and ultimate strengths, deflection, strain, cracking behavior as well as ductility of the beams were evaluated and discussed. To cope with the flexural behavior of the tested beams, a 3D non-linear FE model was simulated. In parametric investigations, the influence of S-NSM reinforcement, the efficacy of the S-NSM procedure, and the structural response ductility are examined. The experimental, numerical, and analytical outcomes show good agreement. The results revealed a significant increase in yield and ultimate strengths as well as improved failure modes.

• Structural Engineering and Mechanics
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• 제83권4호
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• pp.415-433
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• 2022

Eighteen (18) (120×300×2200 mm) beams were prepared and tested to evaluate the shear strength of Glass Fiber Reinforced Concrete (GFRC) beams with no shear reinforcement, and evaluate the effectiveness of various innovative strengthening systems to increase the shear capacity of the GFRC beams. The test variables are the amount of discrete glass fiber (0.0, 0.6, and 1.2% by volume of concrete) and the type of longitudinal reinforcement bars (steel or GFRP), the strengthening systems (externally bonded (EB) sheet, side near-surface mounted (SNSM) bars, or the two together), strengthening material (GFRP or steel) links, different configurations of NSM GFRP bars (side bonded links, full wrapped stirrups, side C-shaped stirrups, and side bent bars), link spacing, link inclination angle, and the number of bent bars. The experimental results showed that adding the discrete glass fiber to the concrete by 0.6%, and 1.2% enhanced the shear strength by 18.5% and 28%, respectively in addition to enhancing the ductility. The results testified the efficiency of different strengthening systems, where it is enhanced the shear capacity by a ratio of 28.4% to 120%, and that is a significant improvement. Providing SNSM bent bars with strips as a new strengthening technique exhibited better shear performance in terms of crack propagation, and improved shear capacity and ductility compared to other strengthening techniques. Based on the experimental shear behavior, an analytical study, which allows the estimation of the shear capacity of the strengthened beams, was proposed, the results of the experimental and analytical study were comparable by a ratio of 0.91 to 1.15.

• 콘크리트학회논문집
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• 제20권5호
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• pp.601-609
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• 2008

본 연구에서는 탄소섬유판 표면 매입 공법 및 외부 부착공법의 장점을 활용하기 위하여, 새로운 형상의 탄소섬유판을 제작하여 실험을 수행하였으며, 탄소섬유판 표면 매입 및 외부 부착이 혼합된 보강 방식의 휨 거동 효과를 분석하였다. 본 연구 결과, 표면매입 (NSM) 및 표면부착 (EBR) 탄소섬유판이 결합한 T형 탄소섬유판으로 보강된 철근콘크리트 부재의 휨 강성 및 극한강도는 섬유판으로 보강되지 않은 보에 비하여 크게 증진되며, 그 최대 증가율은 보강되지 않은 부재의 경우보다 약 347%로 나타났다. 이는 매입 (NSM) 및 부착 (EBR) 탄소섬유판의 상호 구속 효과가 매우 뛰어나 하중을 분배하여 따라서 저항 능력이 크게 개선되는 것으로 판단되었다. 또한 T형 탄소섬유판으로 보강된 철근콘크리트 부재의 파괴는 표면부착 탄소섬유판의 부착 탈락으로 시작되며, 단계적으로 매입 섬유판의 파괴되면서 전단부 콘크리트 피복이 탈락하는 파괴양상으로 나타났다. 매입 탄소섬유판 (NSM CFRP strip) 및 표면부착 (EBR) 탄소판의 극한변형률은 각각 $8,600{\mu}{\varepsilon}{\sim}22,000{\mu}{\varepsilon}$ 및 $7,000{\sim}9,000{\mu}{\varepsilon}$의 범주로 나타나 하중 분배 능력이 우수하며, 따라서 노후 구조물 보강방식으로 효과적인 것으로 판단된다.