CREEP BEHAVIOUR OF STEEL-REINFORCED CONCRETE SPECIMENS

The paper presents the results of investigation of creep and shrinkage of steel-reinforced concrete specimens. For this purpose, parallel tests of specimens made of the same class of concrete but with different reinforcement were carried out. Concrete specimens, specimens reinforced with bar reinforcement frames and steel reinforced concrete specimens with external sheet reinforcement were investigated. The tests were carried out in climatic rooms using spring setups to maintain a constant load acting on the specimens over time. The load on the specimens was selected based on the equality of stresses in the concrete in all series of specimens. The specimens were tested both waterproofed and non-waterproofed, and the effect of waterproofing coating on shrinkage and creep strains was evaluated for different series of specimens. A system was developed to capture information. which allows, in addition to longitudinal shrinkage and creep deformations, to determine transverse deformations, longitudinal deformations along the faces of the specimen to determine the influence of reinforcement and steel of the outer plate, to evaluate the change in longitudinal deformations from the center of the specimen to its edges, to evaluate separately the deformations of concrete and steel plate in steel-reinforced concrete specimens. The analysis of the results allowed a comparative assessment of the influence of conventional bar reinforcement as well as steel sheet of steel-reinforced concrete specimens on creep and shrinkage deformations; the influence of waterproofing coating on the test results in different series was also assessed. Based on the results of this work, extended requirements for experimental and theoretical studies of steel-reinforced concrete specimens with external sheet reinforcement to determine their design stiffnesses were formulated.