Research Of Reinforced Concrete Beams Strengthened With BFRP

Basalt fiber reinforced plastics (BFRP) is an ideal new composite that can beapplied in the civil engineering after the carbon fiber and the glass fiber. Owing to itsprominent advantages such as high strength, good elongation, low price and corrosionresistance, the BFRP is gaining more and more attention.In this paper, experimental research of5RC beams strengthened with BFRP isconducted. The flexural behavior such as bending stiffness, distribution of cracks,ductility and ultimate bearing capacity is compared among the strengthened RC beams.And the influence on strengthened effect is analyzed with the parameters such as layersof BFRP, anchoring measures, and width of the BFRP sheets. Through the experimentalresearch, the conclusions can be summarized as follows.1) During the destruction process of the RC beams strengthened with BFRP, thestrain distribution on section mainly accords with the plane-section assumption.2) The ultimate bearing capacity of the RC beams strengthened with the sameamount of BFRP increases with the increase of width of the BFRP sheets.3) During the course of experiments, the tested beams show good ductility. To acertain degree, widths of the BFRP sheets and anchoring measure have an effect onductility.4) The strain around the end of annular stirrup is insignificantly small all throughthe experiment and this anchoring measure could not effectively prevent the bond-slipfailure of the tested beams in the later stage. Therefore, other anchoring measures arerecommended to be taken at the end of beams. A certain amount of annular stirrup in themid-span could efficiently delay the bond-slip failure.On basis of the experimental research, numerical simulation of the strengthenedbeams is carried out with the help of ANSYS. The calculated results agree well with theexperimental data, which illustrates the effectiveness of the numerical simulation.Furthermore, the influences of reinforcement ratio, widths of the BFRP sheets,eccentricity position, bond length, elastic modulus and secondary stress on bendingperformance of strengthened beams are analyzed. The results indicate that the ductilityof balanced-reinforced beams improves after strengthening. To the beams with lessreinforcement, however, the ductility decreases. Under the condition that the RC beamsstrengthened with the same amount of BFRP, increase the width and reduce the layers of BFRP sheets could accordingly lower the stress concentration. This could prevent thebeams from the bond-slip failure. Eccentricity bond may lead to stress concentration ofBFRP and lower the strengthening effect. The bond length of BFRP has little influenceon reinforcing effect and it only should meet the minimum anchorage lengthrequirement. The ultimate capacity of strengthened beams improves with the increase ofelastic modulus, but the range of the increased ductility decreases. With the increase ofinitial negative load, the improvement of strengthening effect of concrete structuresconsidering load history decreases dramatically.