Change in Relative Deformations in Composite Materials of Centrally Compressed Reinforced Concrete Struts

Introduction. The paper presents experimental data on the change in the values of relative deformations of composite materials of external reinforcement, measured during testing of reinforced concrete pillars. In experimental studies, transverse and longitudinal composite reinforcement was studied, consisting of carbon fabric and carbon laminates (carbon rods). The experimental values of relative strains in composite reinforcement materials make it possible to determine the zones of the most and least stressed sections of composite materials. The purpose of this study is to determine the zones of the most and least loaded areas of composite reinforcement of eccentrically compressed reinforced concrete pillars. This is necessary to create new schemes for the most efficient amplification options. To achieve this goal, the following tasks were completed: five reinforced concrete pillars were manufactured and tested; during the test, strain gauges were glued, which made it possible to determine changes in the relative deformations of composite materials at all levels of loading; all data of relative deformations of composite materials were processed, analyzed and presented in the form of graphs.Materials and methods. In the process of testing reinforced concrete flexible struts, data were obtained on the change in relative deformations in composite materials. The measurements were made by strain gauges with a base of 2 cm glued along the fibers of the composite reinforcement. The zones for measuring relative deformations were chosen according to the nature of the work of the composite material. In total, the work considered the results of testing five reinforced concrete racks, in which carbon fiber fabrics were located in the transverse direction, and carbon rods and lamellas were located in the longitudinal direction.Results. As a result of the study, data on changes in the relative deformations of composite materials were obtained, while the sensors located on the transverse clamps work approximately the same with a relative deformation not exceeding 1.8×10-3. Such deformations are significantly lower than the limiting ones, which is evidence of the incompatibility of the existing structure and the reinforcement material at the limiting stages of loading. With a large gap between the composite clamps, the reinforcement elements practically do not work and the limiting deformations do not exceed 0.6×10-3.Discussion and Conclusions. As a result of processing the change in relative strains characterizing the stress level of composite materials, conclusions were drawn that allow us to state that in the compressed zone the maximum strain does not reach the limit values for composite materials, therefore, the number of transverse reinforcement layers can be reduced. For composite materials located in the longitudinal direction, premature destruction of composite lamellas was established, which made it possible to conclude that there was no joint work of reinforcement materials and concrete of the structure at ultimate breaking loads.