Performance Of Reinforced Concrete Beams Research Articles

Investigation on Flexural Performance of RC Beams Flexurally Strengthened by Soffit-Bonding and Side-Bonding CFRP Sheets

It is an effective way to increase the flexural performance of reinforced concrete (RC) beam by externally bonding fiber reinforcement polymer (FRP) laminate on the soffit of the beam. However, there is little investigation on flexural behavior of RC beam by side-bonding FRP laminates. To investigate the difference of flexural behavior between soffit-bonding and side-binding FRP laminates RC beams, a total of 9 RC beams were tested, including 8 strengthened beams and 1 control beam. The test results showed that: the first crack load of RC beam strengthened by side-bonding CFRP laminates is much bigger than that of RC beam strengthened by soffit-bonding CFRP laminates.The first crack load of side-bonding CFRP laminates beams improved significantly;side-bonding and soffit-bonding methods have the same effect on the flexural stiffness of RC beams with same quantity of CFRP laminates before tension steel rebar yielding. However, side-bonding can remarkably decrease the crack width and change the crack pattern.Side-bonding of CFRP laminates can extend the pre-crack stage of the strengthened beam;the first yielding load and the ultimate load of beams cannot be improved significantly by side-bonding FRP laminates.

Mechanism and Experimental Verification of Degradation of RC Beams Induced by Concrete/Rebar Bonding Failure

From the perspective of Fracture Mechanics, concrete/rebar bonding failure process in reinforced concrete (RC) structures means the decreasing of the crack closure force imposed by rebar in RC beams, which will result in crack propagation, and eventually structural damage. In this paper the crack-arresting mechanism of the concrete/rebar bonding stress in RC beams was analyzed, which was employed to reveal the degradation mechanism of RC beams induced by concrete/rebar bonding failure; and bending tests of RC beams were presented where effects of concrete/rebar bonding failure on bending performance of RC beams had been investigated. The concrete/rebar bonding failure was obtained by wrapping the rebar with different length of plastic film during casting. The results shows effective concrete/rebar bonding is the key to provide crack closure force, which can prevent functional degradation of RC beams.

Contribution à l'étude du renforcement en cisaillement des poutres en béton armé à l'aide de matériaux composites avancés

This paper presents results of an investigation on the shear strengthening of reinforced concrete (RC) beams with externally applied fibre reinforced polymer (FRP) composites. The first part of the study reviews and synthesizes the state of the art in the subject. Also, the requirements and recommendations specified in the Canadian CSA S806-02 standards, the American ACI-440 guidelines, as well as the European fib TG9.3 recommendations are compared with the test results reported in the literature so far. This part of the study indicates that the major parameters involved in the behaviour of RC beams strengthened in shear with FRP were not fully investigated. This can explain the observed discrepancies between the resistance values predicted by the codes and guidelines, and those obtained by tests. This has been the main impetus to carry out an experimental investigation, which is the subject of the second part of this paper. The objective of this experimental investigation was to study the influence of the following parameters on the performance of RC beams strengthened in shear with FRP composites: (i) the FRP ratio, (ii) the transverse steel reinforcement ratio, and (iii) the type of beam (deep versus slender). Results clearly showed the interaction between the FRP composite and the internal transverse steel reinforcement in the shear resistance mechanism. Results also showed the influence of the type of beam on the gain due to FRP on the carrying capacity of the beam.Key words: shear, reinforcement, concrete, composites, experimental, parameters.

Structural repair and strengthening of damaged RC beams with sprayed FRP

This study investigates the load capacity, ductility and energy absorption aspects of reinforced concrete (RC) beams retrofitted with sprayed fiber-reinforced polymer composites (SFRP). It is also intended to assess the feasibility of using SFRP for repair and strengthening of damaged RC beams. A series of three-point bending tests were conducted on both damaged (precracked) and undamaged RC beams to evaluate the performance of deteriorated RC beams after application of SFRP and to examine the influence of SFRP parameters on the performance of RC beams. The parameters in the experimental program were coating thickness, fiber length, fiber materials and fiber loading. The tests yielded complete load–deflection curves from which the increase in load capacity and the energy absorption was evaluated. The results show that SFRP is capable of substantially increasing the load capacity, ductility and energy absorbing capacity strength, and is effective in strengthening and repair of damaged RC beams. The results of the investigation will be used to develop design guidelines governing the use of SFRP for repair and strengthening of damaged RC beams.