• Structural Engineering and Mechanics
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• 제77권5호
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• pp.637-650
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• 2021

The paper presents an investigation of the widely varying mechanical performance and behaviour of steel and Glass Fibre Reinforced Polymer (GFRP) reinforced concrete beams using non-destructive techniques of Acoustic Emission (AE) and Digital Image Correlation (DIC) under four-point bending. Laboratory experiments are performed on both differently reinforced concrete beams with 0.33%, 0.52% and 1.11% of tension reinforcement against balanced section. The results show that the ultimate load-carrying capacity increases with an increase in tensile reinforcement in both cases. In addition to that, AE waveform parameters of amplitude and number of AE hits successfully correlates and picks up the divergent mechanism of cracking initiation and progression of failure in steel reinforced and GFRP reinforced concrete beams. AE activity is about 20-30% more in GFRP-RC beams as compared to steel-RC beams. It was primarily due to the lower modulus of elasticity of GFRP bars leading to much larger ductility and deflections as compared to steel-RC beams. Furthermore, AE XY event plots and longitudinal strain profiles using DIC gives an online and real-time visual display of progressive AE activity and strains respectively to efficaciously depict the crack evolution and their advancement in steel-RC and GFRP-RC beams which show a close matching with the micro-and macro-cracks visually observed in the actual beams at various stages of loading.

• Structural Engineering and Mechanics
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• 제25권1호
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• pp.75-89
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• 2007

Post-earthquake reconnaissance and experimental research indicate that squat reinforced concrete (RC) columns in existing buildings or bridge piers are vulnerable to non-ductile shear failure. Recently, several experimental studies were conducted to investigate upgrading the shear resistance capacity of such columns in order to modify their failure mode to ductile one. Among these upgrading methods is the use of fibre-reinforced polymer (FRP) jackets. One of the preferred analytical tools to simulate the response of frame structures to earthquake loading is the lumped plasticity macromodels due to their computational efficiency and reasonable accuracy. In these models, the columns' nonlinear response is lumped at its ends. The most important input data for such type of models is the element's lateral force-displacement backbone curve. The objective of this study is to verify an analytical method to predict the lateral force-displacement ductility relationship of axially and laterally loaded rectangular RC squat columns retrofitted with FRP composites. The predicted relationship showed good accuracy when compared with tests available in the literature.

• Structural Engineering and Mechanics
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• 제15권3호
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• pp.345-365
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• 2003

The adoption of fibre reinforced polymer (FRP) rebars (whose behaviour is elastic-brittle) in reinforced concrete (RC) cross sections requires the assessment of the influence of time-dependent behaviour of concrete on the load-carrying capacity of these sections. This paper presents a method of computing the load-carrying capacity of sections that are at first submitted to a constant long-term service load and then overloaded up to ultimate load. The method solves first a non-linear visco-elastic problem, and then a non-linear instantaneous analysis up to ultimate load that takes into account the self-equilibrated stress distribution previously computed. This method is then adopted to perform a parametric analysis that shows that creep and shrinkage of concrete increase the load-carrying capacity of the cross section reinforced with FRP and allows for the suggestion of simple design rules.

• Computers and Concrete
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• 제9권3호
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• pp.227-244
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• 2012

A theoretical model for shear strength evaluation of fibrous concrete beams reinforced with stirrups is proposed. The formulation is founded on the theory of plasticity and the stress field concepts, generalizing a known plastic model for calculating the bearing capacity of reinforced concrete beams, to the case of fibrous concrete. The beneficial effect of steel fibres is estimated taking into account the residual tensile strength of fibrous concrete, by modifying an analytical constitutive law which presents a plastic plateau as a post-peak branch. Around fifty results of experimental tests carried out on steel fibrous concrete beams available in the literature were collected, and a comparison of shear strength estimation provided by other semi-empirical models is performed, proving that the numerical values obtained with the proposed model are in very good agreement with the experimental results.

• Steel and Composite Structures
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• 제16권5호
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• pp.481-489
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• 2014

The function of carbon fibre reinforced polymer (CFRP) reinforcement in increasing the ductility of reinforced concrete (RC) deep beam is important in such shear-sensitive RC member. This paper aims to investigate the effect of CFRP-strengthening on the energy absorption of RC deep beams. Six ordinary RC deep beams and six CFRP-strengthened RC deep beams with shear span to the effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were tested till failure in this research. An empirical relationship was established to obtain the energy absorption of CFRP-strengthened RC deep beams. The shear span to the effective depth ratio and growth of energy absorption of CFRP-strengthened deep beam were the significant factors to establish this relationship.

• Structural Engineering and Mechanics
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• 제36권4호
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• pp.421-445
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• 2010

In this paper the formulation of an efficient frame element applicable for nonlinear analysis of 3D reinforced concrete (RC) frames is outlined. Interaction between axial force and bending moment is considered by using the fibre element approach. Further, section warping, effect of normal and tangential forces on the torsional stiffness of section and second order geometrical nonlinearities are included in the model. The developed computer code is employed for nonlinear static analysis of RC sub-assemblages and a simple approach for extending the formulation to dynamic cases is presented. Dynamic progressive collapse assessment of RC space frames based on the alternate path method is undertaken and dynamic load factor (DLF) is estimated. Further, it is concluded that the torsional behaviour of reinforced concrete elements satisfying minimum standard requirements is not significant for the framed structures studied.

• Structural Engineering and Mechanics
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• 제73권4호
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• pp.381-395
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• 2020

Study on the inelastic response of bare and masonry infilled Reinforced Concrete (RC) frames repaired using Carbon Fibre Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) subjected to quasi- static loading is presented in the work. The hysteresis behaviour, stiffness retention, energy dissipation and damage index are the parameters employed to analyze the efficacy of FRP strengthening of bare and brick in-filled RC frames. It is observed that there is a significant improvement in load carrying capacity of brick infilled frame over bare RC frame. Also FRP strengthened brick infilled frame performs much better than FRP repaired bare frame under quasi static loading. Repair and retrofitting of brick infilled RC frame shows an improved load carrying and damage tolerance capacity than control frame.

• Advances in concrete construction
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• 제15권5호
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• pp.321-331
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• 2023

The effect of fibre-reinforced polymer (FRP) strengthening on the behaviour of reinforced concrete (RC) beams with web openings is studied. It has been observed that the load-carrying capacity and deflection in the presence of an opening reduced by approximately 50% and 75%, respectively. Three-dimensional nonlinear finite models are first validated with the results obtained from experimental data. Thereafter, a series of parametric studies are conducted for the beam with an opening. In the study, it is observed that a square opening shape is critical in comparison to the elliptical and circular-shaped opening. The web opening located near the support is found to be critically compared to the opening in the middle of the beam. Given the critical opening shape situated at the critical location, the increase in FRP layers enhances the load-deformation behaviour of the FRP-wrapped RC beam. However, the load-deformation responses are not significantly improved beyond a certain threshold value of FRP layers.

• Structural Engineering and Mechanics
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• 제24권1호
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• pp.1-18
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• 2006

Strengthening of existing old structures has traditionally been accomplished by using conventional materials and techniques, viz., externally bonded steel plates, steel or concrete jackets, etc. Alternatively, fibre reinforced polymer composite (FRPC) products started being used to overcome problems associated with conventional materials in the mid 1950s because of their favourable engineering properties. Effectiveness of FRPC materials has been demonstrated through extensive experimental research throughout the world in the last two decades. However there is a need to use refined analytical tools to simulate response of strengthened system. In this paper, an attempt has been made to develop a numerical model of strengthened reinforced concrete (RC) beams with FRPC laminates. Material models for RC beams strengthened with FRPC laminates are described and verified through a nonlinear finite element (FE) commercial code, with the help of available experimental data. Three dimensional (3D) FE analysis has been performed by assuming perfect bonding between concrete and FRPC laminate. A parametric study has also been performed to examine effects of various parameters like fibre type, stirrup's spacing, etc. on the strengthening system. Through numerical simulation, it has been shown that it is possible to predict accurately the flexural response of RC beams strengthened with FRPC laminates by selecting an appropriate material constitutive model. Comparisons are made between the available experimental results in literature and FE analysis results obtained by the present investigators using load-deflection and load-strain plots as well as ultimate load of the strengthened beams. Furthermore, evaluation of crack patterns from FE analysis and experimental failure modes are discussed at the end.

• 한국강구조학회 논문집
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• 제10권2호통권35호
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• pp.201-209
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• 1998

강섬유보강 적층복합구조물에서 온도의 변화는 구조물의 응답에 중요한 영향을 미칠수 있다. 온도의 급작스런 변화는 재료의 강도와 성질을 현저히 저하시켜 구조물의 대변형, 좌굴, 고응력상태를 유발하는 중요한 인자가 된다. 본 연구에서는 등분포로 재하된 온도하중에 의한 적층복합판의 온도좌굴에 관한 해석을 수행하였다. 전단변형의 효과를 정확히 고려하기위해 5개의 변수로 구성된 고차전단변형이론을 적용하였다. 적층판의 배열각도, 적층판의 수, 폭-두께비의 변화, 형상비의 변화에 따른 임계좌굴온도를 구하여 1차전단변형이론에 의한 결과와 고전적이론에 의한 결과와 비교분석하였다.