Issue 46

H. Zhu et alii, Frattura ed Integrità Strutturale, 46 (2018) 361-370; DOI: 10.3221/IGF-ESIS.46.33 369 D ISCUSSION AND CONCLUSION RP as a novel building material suggests favourable performance in reinforcing reinforced concrete beams. To prevent the failure of binding materials, embedded CFRP plate strengthening is an advantageous method [13]. To fully understand the performance of CFRP plate, multi-aspect studies need to be made. The application of finite element software can reduce test materials and workload. Many scholars have studied the functions of finite element software in the simulation of CFRP plate strengthening. Dirar et al. [14] analyzed the shear capacity of reinforced concrete beams using finite element analysis method and compared the simulated values and test values of shear force, shear force-deflection curve, crack mode and failure mode via modeling to understand the shear capacity. Taghia et al. [15] explored the influence of CFRP plate on reinforced concrete short columns using finite element software, studied different aspects of constraint effect such as difference of sectional dimension, number of carbon fiber cloth and volume ratio of carbon fiber cloth, and found that outside sticking of carbon fiber cloth was quite effective in improving the axial strength and ductility of concrete short columns. In this study, the model was established using ANSYS. To verify the reliability of the model, the test values and simulated values of three beams were compared, and it was found that the two groups of data basically fitting. The existence of error might be because the test beams were affected by factors such as temperature and proportion of concrete, the finite element model ignored the bond slipping between different interfaces of the beams, and partial parameters were excessively ideal. But overall, the results could verify that the finite element model had high accuracy and reliability. To study the mechanical performance of embedded CFRP plate reinforcement method, six reinforcement methods which involved different length of CFRP plate, number of CFRP plate, number of grooves and shear span ratio were compared. The results demonstrated that different reinforcement methods had different influences on the carrying capacity and failure mode of beams; proper increase of length of CFRP plate could avoid the debonding failure of the protective layer of concrete; multiple plates and grooves could increase the surface of plates and inhibit the growth of cracks at the bottom of concrete, but too many grooves was not beneficial to the integral rigidity of beams and might lead to decrease of the ultimate carrying capacity (for example, beam E); the larger the shear span ratio, the higher the ultimate carrying capacity of beams and the lower the possibility of deformation (for example, beam F). The beams except beam A had debonding failure, which might be because the sufficient length of anchoring of the CFRP plates of beam A reduced the possibilities of debonding failure. It indicated that the embedded length of the CFRP plate might be in an obvious correlation with the possibilities of debonding failure. The comparison of strain between the rebars, concrete and CFRP plate suggested that embedded CFRP plate reinforcement was significantly effective in increasing the strain of the beams, and the strain of the CFRP plate was larger than that of the rebars. In conclusion, embedded CFRP plate strengthening was effective in enhancing the mechanical performance of reinforced concrete beams. Embedded CFRP plate strengthening beams with favourable mechanical performance has a broad development prospect in repairing old buildings. In this study, the mechanical performance of the beams which applied different strengthening methods was compared in aspects of the number, size, grooving mode and shear span ratio of the CFRP plate after the effectiveness of the model was verified. The results demonstrated that the ultimate carrying capacity of the embedded CFRP plate strengthening beams was significantly superior to that of ordinary reinforced concrete beams, the reinforcement method of two CFRP plates and two grooves was the best, and the larger the shear span ratio, the higher the carrying capacity and the lower the possibility of deformation. Embedded CFRP reinforcement technology has more possibilities, and its application values need to be explored through more studies in the future. REFERENCES [1] Motavalli, M., Czaderski, C. and Pfyl-Lang, K. (2011). Prestressed CFRP for Strengthening of Reinforced Concrete Structures — Recent Developments at Empa Switzerland. Journal of Composites for Construction, 15(2), pp. 194- 205. [2] Raoof, S.M., Koutas, L.N. and Bournas, D.A. (2017). Textile-reinforced mortar (TRM) versus fibre-reinforced polymers (FRP) in flexural strengthening of RC beams. Construction & Building Materials, 151, pp. 279-291. [3] Khelifa, M. and Celzard, A. (2014). Numerical analysis of flexural strengthening of timber beams reinforced with CFRP strips. Composite Structures, 111(1), pp. 393-400. [4] Rezazadeh, M., Costa, I. and Barros, J. (2014). Influence of prestress level on NSM CFRP laminates for the flexural strengthening of RC beams. Composite Structures, 116 (1), pp. 489-500. F