• Computers and Concrete
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• 제33권2호
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• pp.163-173
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• 2024

Fiber-reinforced polymers (FRP) have a proven strength enhancement capability when installed into Reinforced Concrete (RC) beams. The brittle failure of traditional FRP strengthening systems has attracted researchers to develop novel materials with improved strength and ductility properties. One such material is that known as polyethylene terephthalate (PET). This study presents a numerical investigation of the flexural behavior of reinforced concrete beams externally strengthened with PET-FRP systems. This material is distinguished by its large rupture strain, leading to an improvement in the ductility of the strengthened structural members compared to conventional FRPs. A three-dimensional (3-D) finite element (FE) model is developed in this study to predict the load-deflection response of a series of experimentally tested beams published in the literature. The numerical model incorporates constitutive material laws and bond-slip behavior between concrete and the strengthening system. Moreover, the validated model was applied in a parametric study to inspect the effect of concrete compressive strength, PET-FRP sheet length, and reinforcing steel bar diameter on the overall performance of concrete beams externally strengthened with PET-FRP.

• 한국구조물진단유지관리공학회 논문집
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• 제14권1호
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• pp.125-132
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• 2010

최근 건설 사업에서 FRP를 단순 부착하여 구조물을 보강하는 공법은 현재 가장 널리 사용되고 있는 보수보강법이다. 본 논문에서는 FRP로 보강된 철근콘크리트 구조물은 지속하중을 받고 있기 때문에 크리프와 건조수축의 영향을 받는다. 이로 인하여 FRP의 보강효과도 달라지며, 처짐 및 변형의 회복성능, 잔존 내력 역시 크게 달라진다. 따라서 CFRP, GFRP가 휨성능에 영향을 미치는 보강 성능을 파악하고, 일정 시간이 흐른 후 하중을 제거하여 장기 변형 및 처짐의 회복성능을 파악하고, 잔존하는 내력을 알아보고자 정적 재하 실험을 수행하였다. 실험한 결과, FRP 보강 실험체는 즉시 처짐을 제어하는 측면은 매우 효율적이고, 즉시변형 회복량 또한 즉시 변형량보다 큰 결과를 보였다. 잔존강도 실험을 통하여 CFRP로 보강된 실험체가 가장 큰 내력을 가지는 것으로 나타났다. FRP로 보강된 보는 지속하중에 의한 부착성능 및 잔존내력에는 영향이 없었던 것으로 판단된다.

• Steel and Composite Structures
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• 제31권2호
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• pp.113-123
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• 2019

In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of $8.5g/m^2$ to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites.

• Steel and Composite Structures
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• 제35권5호
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• pp.687-699
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• 2020

This paper focus on the buckling restrained braces (BRBs) with new casing members (CMs). Seven BRBs with CMs consisting of precast concrete modules (PCMs) were tested to investigate the effects of CMs on the cyclic performance of BRBs. The PCMs consisted of plain and reinforced concrete casted into wooden or steel molds than they were located on the core plate (CP) via bolts. There were 14 or 18 PCMs on the CP for each BRBs. The technique of the PCMs for the CM provides that the BRBs can be constructed inside the steel or reinforced concrete (RC) structures. In this way, their applications may be rapid and practical during the application of the retrofitting. The test results indicated that the cyclic performance of the BRBs was dominated by the connection strength and confinement of the PCMs. The BRBs with PCMs wrapped with fiber reinforced polymers (FRPs) sustained stable hysteretic performance up to a CP strain of 2.0 %. This indicates that the new designed BRBs with PCMs were found to be acceptable in terms of cyclic performance. Furthermore, the connection details, isolation materials and their application techniques have been also investigated for the improved BRB design in this study.

• Smart Structures and Systems
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• 제26권4호
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• pp.403-418
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• 2020

In recent years, the use of Fiber Reinforced Polymers (FRPs) as one of the most common ways to increase the strength of concrete samples, has been introduced. Evaluation of the final strength of these specimens is performed with different experimental methods. In this research, due to the variety of models, the low accuracy and impact of different parameters, the use of new intelligence methods is considered. Therefore, using artificial intelligent-based models, a new solution for evaluating the bond strength of FRP is presented in this paper. 150 experimental samples were collected from previous studies, and then two new hybrid models of Imperialist Competitive Algorithm (ICA)-Artificial Neural Network (ANN) and Artificial Bee Colony (ABC)-ANN were developed. These models were evaluated using different performance indices and then, a comparison was made between the developed models. The results showed that the ICA-ANN model's ability to predict the bond strength of FRP is higher than the ABC-ANN model. Finally, to demonstrate the capabilities of this new model, a comparison was made between the five experimental models and the results were presented for all data. This comparison showed that the new model could offer better performance. It is concluded that the proposed hybrid models can be utilized in the field of this study as a suitable substitute for empirical models.