• Coupled systems mechanics
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• v.10 no.2
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• pp.161-184
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• 2021

Strengthening of reinforced concrete beams with externally bonded fiber reinforced polymer plates/sheets technique has become widespread in the last two decades. Although a great deal of research has been conducted on simply supported RC beams, a few studies have been carried out on continuous beams strengthened with FRP composites. This paper presents a simple uniaxial nonlinear analytical model that is able to accurately estimate the load carrying capacity and the behaviour of damaged RC continuous beams flexural strengthened with externally bonded prestressed composite plates on both of the upper and lower fibers, taking into account the thermal load. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the damaged concrete beam, the FRP plate and the adhesive layer. The flexural analysis results and analytical predictions for the prestressed composite strengthened damaged RC continuous beams were compared and showed very good agreement in terms of the debonding load, yield load, and ultimate load. The use of composite materials increased the ultimate load capacity compared with the non strengthened beams. The major objective of the current model is to help engineers' model FRP strengthened RC continuous beams in a simple manner. Finally, this research is helpful for the understanding on mechanical behaviour of the interface and design of the FRP-damaged RC hybrid structures.

• Computers and Concrete
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• v.33 no.2
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• pp.121-136
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• 2024

In recent times, there has been a growing need to retrofit and strengthen reinforced concrete (RC) structures that have been damaged. Numerous studies have explored various methods for strengthening RC beams. However, there is a significant dearth of research investigating the utilization of ultra-high-performance concrete (UHPC) for retrofitting damaged RC beams within a concrete frame. This study aims to develop a finite element (FE) model capable of accurately simulating the nonlinear behavior of RC beams and subsequently implementing it in an RC concrete frame. The RC frame is subjected to loading until failure at two distinct degrees, followed by retrofitting and strengthening using Ultra high performance shotcrete (UHPS) through two different methods. The results indicate the successful simulation of the load-displacement curve and crack patterns by the FE model, aligning well with experimental observations. Novel techniques for reinforcing deteriorated concrete frame structures through ABAQUS are introduced. The second strengthening method notably improves both the load-carrying capacity and initial stiffness of the load-displacement curve. By incorporating embedded rebars in the frame's columns, the beam's load-carrying capacity is enhanced by up to 31% compared to cases without embedding. These findings indicate the potential for improving the design of strengthening methods for damaged RC beams and utilizing the FE model to predict the strengthening capacity of UHPS for damaged concrete structures.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.521-543
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• 2015

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.723-736
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• 2019

The efficacy of a technique for the rehabilitation and strengthening of RC beam-column connections damaged due to cyclic loading was investigated. The repair mainly uses epoxy resin infused under pressure into the damaged region to retrieved back the lost capacity and then strengthening using fiber reinforced polymer (FRP) sheets for capacity enhancement. Three common types of reduced scale RC exterior beam-column connections namely (a) beam-column connection with beam weak in flexure (BWF) (b) beam-column connections with beam weak in shear (BWS) and (c) beam-column connections with column weak in shear (CWS) subjected to reversed cyclic loading were considered for the experimental investigation. The rehabilitated and strengthened specimens were also subjected to similar cyclic displacement. Important parameters related to seismic capacity such as strength, stiffness degradation, energy dissipation, and ductility were evaluated. The rehabilitated connections exhibited equal or better performance and hence the adopted rehabilitation strategies could be considered as satisfactory. Confinement of damaged region using FRP sheet significantly enhanced the seismic capacity of the connections.

• Earthquakes and Structures
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• v.16 no.3
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• pp.253-263
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• 2019

The efficacy of a galvanized steel wire mesh (GSWM) as an alternative material for the rehabilitation of RC beam-column connections damaged due to reversed cyclic loading was investigated. The repair mainly uses epoxy resin infused under pressure into the damaged zone and then confined using three types of locally available GSWM mesh. The mesh types used herein are (a) Weave type square mesh with 2mm grid opening (GWSM-1) (b) Twisted wire mesh with hexagonal opening of 15 mm (GSWM-2) and (c) welded wire mesh with square opening of 25 mm (GSWM-3). A reduced scale RC beam-column connection detailed as per ductile detailing codes of Indian Standard was considered for the experimental investigation. The rehabilitated specimens were also subjected to similar cyclic displacement. Important parameters related to seismic capacity such as strength, stiffness degradation, energy dissipation, and ductility were evaluated. The rehabilitated connections exhibited equal or better performance and hence the adopted rehabilitation strategies could be considered as satisfactory. Confinement of damaged region using GSWM-1 significantly enhanced the seismic capacity of the connections.

• Advances in materials Research
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• v.8 no.3
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• pp.197-217
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• 2019

In this study, the interfacial stresses in RC beams strengthened by externally bonded prestressed GFRP laminate are evaluated using an analytical approach, based on the equilibrium equations and boundary conditions. A comparison of the interfacial stresses obtained from the present analytical model and other existing models is undertaken. Otherwise, a parametric study is conducted to investigate the effects of geometrical and material properties on the variation of interfacial stresses in damaged RC beams strengthened by externally bonded prestressed GFRP laminate. The results obtained indicate that the damage degree has little effect on the maximum shear stress, with a variation less than 5% between the damaged and undamaged RC beams. However, the results also reveal that the prestressing level has a significant effect on the interfacial stresses; hence the damaged RC beam strengthened with an initial prestressing force of 100 kN gives 110% higher maximum shear stress than the damaged RC beam strengthened with an initial prestressing force of 50 kN. The values of shear stress obtained by the analytical approach are approximately equal to 44% of those obtained from the numerical solution, while the interfacial normal stresses predicted by the numerical study are approximately 26% higher than those calculated by the analytical solution.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.548-551
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• 2004

The main purpose of this study is to estimate the internal temperature of RC beam under fire. For this purpose, the finite difference method was used. In the previous studies, the structural behavior of fire damaged RC beams was investigated through experiments. The result was concluded that The high temperature affects the properties of concrete such as the elastic modulus, the compressive strength. The internal temperature Estimation of the concrete is helpful for understanding the structural behavior of fire damaged RC beams. Especially, high strength concrete has more spalling than normal strength one. So, this study is performed analysis of internal temperature of RC beam considering spalling.

• Steel and Composite Structures
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• v.11 no.3
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• pp.207-223
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• 2011

The results of an experimental investigation are presented in this paper for retrofitting of shear damaged reinforced concrete beams by using U shaped CFRP strips. The experimental program is consisted of seven shear deficient T cross sectioned 1/2 scale simply supported beam specimens. One beam was used as reference specimen, and the remaining six specimens were tested in two stages. At the first stage, specimens were shear damaged severely, and then were retrofitted by using CFRP strips with or without fan type anchorages. Finally, retrofitted beams were tested up to failure. Three different CFRP strip spacing were used such as 125 mm, 150 mm, and 200 mm. The effect of anchorages on shear strength and behavior of the retrofitted specimens is investigated. CFRP strips without anchorages improved the shear strength, but no flexural failure mode was observed. Specimens showed brittle shear failure due to peeling of CFRP strip from RC beam surface. Shear damaged specimens retrofitted with anchoraged CFRP strips showed improved shear strength and ductile flexural failure. Maximum strains at anchoraged strips were approximately 68% larger than that of strips without anchorages.

• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.49-61
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• 2022

This paper presents an experimental investigation into the effectiveness of using carbon fibre reinforced polymer (CFRP) and steel plates to repair damaged reinforced concrete (RC) beams with circular web openings at shear zones. It highlights the effectiveness of externally bonded CFRP and steel plates in repairing damaged RC beams by analysing the repaired beams'load capacity, deflection, strain, and failure mode. For the experiment, a total of five beams were used, with one solid beam as a control beam and the other four beams having an opening near the shear zone. Two beams with openings were repaired using inclined and vertical configuration CFRP plates, and the other two were repaired using inclined and vertical configuration steel plates. The results confirm the effectiveness of CFRP and steel plates for repairing damaged RC beams with circular openings. The CFRP and steel plates significantly increase ultimate capacity and reduce deflection under the openings. The inclined configuration of both CFRP and steel plates was more effective than the vertical configuration. Using an inclined configuration not only increases the ultimate capacity of the beams but also changes the mode of failure from shear to flexural.

• Architectural research
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• v.10 no.2
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• pp.37-42
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• 2008

This study is to get the proper evaluation of the residual property of reinforced concrete beam exposed to fire. This study focused on the strength resistance and analytical evaluation of RC members exposed high temperature. And this study is the basis analytical research to conduct the other studies. To analysis by the finite element method, the Total-RC program was used to analysis it and the Total-Temp program was also used to analysis the temperature distributions at the section. All of results were compared with the pre-existing experimental data of simple supported beam. Using it, the parameters influencing the structural capacity of the high temperature-damaged RC members and residual strength estimation are investigated. The temperature distribution and the structural capacity at the section are calculated in this step. An application of this method is compared with the heating test result and residual property test for simple supported beam which is subjected to ISO 834 test fire. The results of this study are as follows; 1) The loads-displacement relationship of RC beam, considering initial thermal stress of cross section and heat transfer analysis are estimated comparing analytical value with pre-existing experimental results. 2) by the heating time (0, 1, 2 hours), the results of analysis with parameters show that the load capacity exposing at fire is affected.