Study On The Bending Behavior Of RC Beams Strengthened With BFRP Considering The Secondary Loading

Basalt Fiber-Reinforced Polymer (abbr. BFRP) is a new kind ofcomposite materials which is enhanced by basalt fiber. As a kind ofreinforced composite materials applied in the foundation engineering,BFRP has proper development prospects, especially when it is used in thefield of building reinforcement and reinforcing. Compared with the carbonfiber and others, BFRP has the advantage of low cost.However, the existing experimental and theoretical study ofreinforcing behavior of reinforced concrete structures (or components)strengthened with BFRP is still deficient at present. Based on theoreticalanalysis, numerical simulation and experimental research, the ultimateflexural capacity of BFRP reinforced beams is studied in this paper. Themain work and conclusions of this paper are summarized as follows:1Based on the existing research achievements, the stresscharacteristics, failure characteristics and influence parameters of FRPreinforced beams are analyzed theoretically. Taking the secondary loadinginto account, the normal section bearing capacity formulas and the criticalBFRP ratio are derived respectively aiming at the three failure models, which are BFRP breaking, concrete crush and central crack damage causedby middle cracks. Finally, an example is given to show the calculationprocess in detail.2Considering the secondary loading, the affect of unloading and non-unloading should be taken into account when the hysteretic strain of BFRPis calculated. That is to say, the influence of residual strain can not beignored when reinforcement is carried out after unloading. In this way, aformula is derived to calculate the hysteretic strain of BFRP according tothe different loading history and different unloading degree withexperimental data proving its rationality.3Based on the experimental research on the BFRP reinforced beamsregard to different loading history and different unloading degree, theinfluences of hysteretic strain, deflection and the improvement of theultimate flexural capacity such as different loading history, differentunloading degree and different layers of BFRP are discussed respectively.The work above also provides experimental data and theoretical basis to theimprovment of BFRP reinforcement theory.4Based on the existing experimental data of FRP reinforced beamsand the experimental data in this paper, the calculation modes of theultimate flexural capacity from the two prevailing strengthening codes andin this paper were comparatively analyzed. The results show that thetheoretical values from the calculation model presented in this paper agrees with the experimental results better, and the discreteness of the calculationresults is smaller. It has been proved that the calculation model presented inthis paper is rational.