The high-tech and effective method of strengthening reinforced concrete structures with CFRP materials with preliminary modification of the cross-section shape

It is known that the effectiveness of reinforcement with CFRP composite materials of reinforced concrete structures of round or oval sections is significantly higher than rectangular or square ones due to the uneven distribution of internal limiting pressure in the latter. This study is devoted to the study of the effectiveness of a new method of strengthenet based on a preliminary change in the shape of reinforced concrete and concrete columns of square section. The sharp corners of the columns create a concentrating internal limiting stress in the CFRP composite cage, while the amplification system collapses prematurely, and the amplification efficiency is greatly reduced. To comprehensively solve this problem, the authors have manufactured, strengthened and tested a number of reinforced concrete columns with different variants of CFRP composite reinforcement. For the purity of the experiment, reference racks were also made, not reinforced, and reinforced with CFRP composite clips without rounding. All prototypes were made of the same materials, as well as strengthened and tested using the same techniques. The paper describes the features of traditional and modern methods of composite strengthenet of reinforced concrete columns, analyzes the main disadvantages of existing strengthenet methods and, based on this, presents a new strengthenet method that allows more efficient use of composite materials in the transverse direction. The new strengthenet method is described in detail, the main schemes and procedure for performing strengthenet work are presented. The final stage of the work is the main results of an experimental study, where the characteristics of reference samples were compared with similar structures strengthened in the transverse direction with CFRP composite materials. The experimental results show that the proposed amplification method is highly effective. For the best effect, it is proposed that the material used for rounding has higher strength and less deformability compared to concrete columns.