Theoretical Analysis Of RC Beams Strengthened With Bamboo Strips

The researches about the reinforced concrete (RC) beams strengthened with bamboo strips at home and abroad shows that using bamboo strips to reinforce the RC component can save a lot of construction funds, reduce the damage to the environment, and has great economic benefit and environment benefit.RC beams strengthened with bamboo strips are analyzed theoretically based on the plane cross-section assumption. From the aspects of the load applied on the beam when the first crack appears, the initial bending stiffness, and the ultimate flexural strength of the beam, the different performances about the RC beams strengthened with multi-layer bamboo strips are compared. The example shows that the theoretical results coincide well with the experiment and FEM ones, which implies the correctness of the theoretical solution obtained in this paper. The stress calculation formulas are given. These formulas can also be used to calculate the stress in the RC beam strengthened with multi-layer bamboo strips. At the same time, through comparing the different performances about the RC beam and the RC ones strengthened with multi-layer bamboo strips, we can find out the effect of this strengthened RC beams, and offer a rational suggestion for the optimization design. The main conclusions are as follows:(1) The RC beams strengthened with bamboo strips are analyzed theoretically. The calculation formulas about the load applied on the beam when the first crack appears, the initial bending stiffness and the ultimate flexural strength of the beams are given. The deviations between the theoretical, test and FEM values are compared through examples, which implies the correctness of the theoretical solution.(2) The theoretical results show that the load applied on the beam when the first crack appears was increased by 44.5～51.6% after strengthened by bamboo strips. The initial bending stiffness of the strengthened beams was increased by 13.7～35.4%. The ultimate flexural strength of the strengthened beams was also increased by 25.1～69.3%. It shows that the performance of the RC beams will be obviously improved after strengthened by bamboo strips.(3) Throughing the size of the radius of curvature in the theoretical analysis, we can find that the ultimate flexural strength of the beam strengthened with one layer bamboo strips was just increased by 25.1%, but the deflection in the middle of the beam is more noticeable. It belongs to ductile fracture. On the contrary, the deflection of the beam strengthened with two and three layers bamboo strips is not obvious, and they belongs to brittle failure. This kind of circumstances should be avoided in the engineering.(4) When the RC beams strengthened with multi-layer bamboo strips reach ultimate flexural strength, the tensile strength of the bamboo strips did not meet the restrictions. Instead, the stress of structural adhesive reaches the limit. Bamboo strips were stripped from concretes in the experiment can prove this point. It follows that improving the performance of structural adhesive or strengthening the immobilization between bamboo strips and concretes at the end of the beam, can further improve the reinforcement of bamboo strips.The main conclusions of the paper have a certain theoretical and practical significance on the study of the principles on strengthened RC beams and the construction technology about the RC beams strengthened with multi-layer bamboo strips. This paper can also provide theoretical bases and guidances for the engineering.