Issue 46

H. Zhu et alii, Frattura ed Integrità Strutturale, 46 (2018) 361-370; DOI: 10.3221/IGF-ESIS.46.33 367 A NALYSIS ON THE MECHANICAL PERFORMANCE o determine the best reinforcement method of CFRP plate, different embedded CFRP plates were studied using finite element model. Taking reinforced concrete beam as an example, six reinforcement methods were designed to analyze and compare the mechanical performance of the beam. The model parameters are shown Tab. 4. No. of test specimen Reinforced concrete beam A B C D E F Size of test specimen (mm) 200*250* 1800 200*250* 1800 200*250* 1800 200*250* 1800 200*250* 1800 200*250* 1800 200*250* 1800 Size of CFRP plate (mm) - 1.2*20*1800 1.2*20*900 1.2*20*900 1.2*20*600 1.2*20*600 1.2*20.900 Number of CFRP plate (n) - 1 2 2 3 3 2 Number of grooves (n) - 1 1 2 1 3 2 Size of groove (mm) - 20*20*1800 20*20*900 20*20*900 20*20*600 20*20*600 20*20*900 Shear span ratio (a/h0) - 2.32 2.32 2.32 2.32 2.32 2.73 Spacing between grooves (mm) - - - 80 - 60 80 Table 4 : The model parameters. Fig. 5 shows the load-deflection curves of the strengthening beams of different kinds. With the increase of the load, the load-deflection curves of different beams gradually changed: the concrete at the bottom of the beam fractured, and the mechanical performance of the beam changed. The deflection of the strengthening beams increased slower than that of the non-strengthening beams, indicating that CFRP plate could effectively reduce the mid-span displacement of beams. Different reinforcement methods of beams had different influence on the carrying capacity and failure modes of beams. In the aspect of groove mode, the effect of multiple grooves and plates was better than that of single groove and multiple plates. CFRP plate could inhibit the growth of cracks, but too many grooves was not beneficial to the integral rigidity of beams; therefore two grooves was the best. In the aspect of shear span ratio, the larger the shear span ratio. Tab. 5 shows the ultimate carrying capacity, improvement amplitude and failure mode of the strengthening beams of different kinds. Under the same load, the mid-span displacement of the strengthening beams was smaller than that of the non- strengthening beams. The improvement amplitudes of beam C and F was the largest, but beam F was more obvious. I indicated that the larger the shear span ratio, the better then reinforcement effect. As to the failure mode, beam E had bending failure, and the other beams had debonding failure. It might be because the increased number of grooves. Moreover debonding failure of the protective layer of concrete can be avoided only when the length of the CFRP plate was enough. The CFRP plate, rebars and concrete strains of the reinforced beam, beam C and beam F were further compared, and the comparison results are shown in Fig. 6. It could be noted from Fig. 6 that the strain value of the CFRP plate strengthening beam was larger than that of the reinforced concrete beam. Under the same load, the strain of the CFRP plate was larger than that of the rebars as the bottom tension was bore by the CFRP plates and rebars after the cracking of concrete, the relative distance of the CFRP plates was large, and the elasticity modulus was low. The strain of beam F was larger than the strain of beam C, indicating that the larger the shear span ratio, the better the mechanical performance. T