Experimental study and finite element analysis on the flexural performance of predamaged concrete beams strengthened with PET straps

Polyethylene Glycol Terephthalate (PET), as a new type of reinforcement material, has the advantages of economy, environmental protection, and convenient construction for strengthening reinforced concrete structures. To study the effectiveness of PET strengthening damaged reinforced concrete beams, six reinforced concrete beams were designed. Considering the influence of parameters such as the pre-damage index and PET area, a bending test was carried out to study the failure characteristics, bearing capacity, bending deflection, ductility, and strain of PET and concrete. According to the test parameters, the ABAQUS simulation model was established to study the failure mode, bearing capacity and ductility of the specimens. Compared with the test results, the two have high consistency. On this basis, the parameters such as the reinforcement area, the number of reinforcement layers, and the reinforcement method of the plastic steel strip were expanded and analyzed. The results show that compared with the reference specimen L-0, the ultimate bearing capacity of the L-1 specimen is increased by 12.37 %, the ultimate displacement is increased by 29.3 %, and the displacement ductility coefficient is increased by 35.5 %. It shows that PET can effectively inhibit the generation and development of cracks and improve the ultimate bearing capacity and ductility of components. Under the same strengthening conditions, the flexural bearing capacity and ductility of the strengthened specimens decrease with the increase of the pre-damage index. Under the condition of damage reinforcement with the same pre-damage index, with the increase of PET reinforcement area and reinforcement layer number, the bearing capacity of the specimen is obviously enhanced. When multi-layer reinforcement is adopted, the stress distribution is the most uniform and the material performance is the most fully exerted when the number of reinforcement layers is 2 layers compared with other layers. Comparing the ultimate bearing capacity, ductility performance, and stress distribution of the reinforced structure, it is found that the fully wrapped plastic steel strip reinforcement method is the best reinforcement method.