Bearing Capacity of Strengthened Reinforced Concrete Beams
Authors: Kinasz Roman , Mazurak Andrii , Kovalyk Ivan , Mazurak Rostyslav , Tsap Orest 
Published: December 2020

Abstract
The need reinforcement building structures during operation arises not only during reconstruction but also because various damages. The various combination reasons for the need reinforcement, as well as the type and condition the building structures necessitates the use different ways reinforcement. Today, it is still effective to reinforce the bending elements of reinforced concrete structures with reinforced concrete and shotcrete. Therefore, the purpose of our work is to improve the calculation method, to evaluate the load-bearing capacity reinforced concrete beams, taking into account residual deformations and stresses of concrete and reinforcement. Methods for reinforcing reinforced concrete structures are described in detail in literature and are widely used in construction. The proposed experimental studies consisted 15 reinforced concrete beams with design dimensions 2300x200x80 (120; 145). Nine beams were reinforced with reinforced concrete, five beams reinforced with concrete and one beam without reinforcement. The test specimens were amplified by the extension of the lateral surfaces at different loading levels, namely 0.0; 0.3; 0.45; 0.6 from the devastating moment. To create such levels of load, a specially designed metal rig was used, transmitting its effect to the test beam in the form of two concentrated forces in thirds of the span. Before the reinforcement of the contact beams of the test beams, adhesive layers were applied, metal anchors were affixed to which the reinforcement frames were fastened. The bearing capacity of the normal cross sections of the experimental, reinforced concrete beams was evaluated according to the proposed algorithm, based on the deformation model. The algorithm is adapted to calculate reinforced concrete beam structures in various ways (extension, shirt or clip). In the calculation method, the joint work of the layers of “old” and “new” concrete was taken into account by assigning all elements of the section a single bend. Adopted structural and technological solutions in the test beams, namely the use of shotcrete concrete, adhesive priming, and glued metal anchors (Ø 8mm) protruding from the surface at 35mm, ensured the matrix and reinforcement layers work together. Based on the experimental studies, the analysis of the calculated data with the experimental results was performed. The proposed calculation method well estimates the bearing capacity of the normal cross sections reinforced with reinforced shotcrete concrete reinforced concrete beams, the difference reaches no more than 6%. However, as the analysis of the results of the studies in the cross sections of the test pieces of the main and reinforced part of the beam shows, the experimental and calculated values of concrete deformations have a greater divergence, similarly this phenomenon is observed in the results of deformation of reinforcement. The discrepancy between the calculated and experimental values of the main and reinforced part of the beam is revealed due to the delayed inclusion in the work of reinforcement of the reinforced part, which should be taken into account in the following studies.