Previsão da vida à fadiga das barras de aço por meio do modelo de Tanaka e Mura e da teoria da distância crítica

Abstract

Steel reinforcement bars (rebars) are determinant in the fatigue strength of reinforced concrete bridges when the concrete is in good condition and can rupture without apparent damage to the structure. The increasing volume of traffic in bridges added to the lack of maintenance, makes the conditions of the steel bars in these structures are unknown. Since it is not possible to inspect only the rebars, fatigue life prediction models can be used to calculate how many load cycles they still support. This research aim to predict the fatigue life of hot rolled, cold worked and quenched and self-tempered rebars by the Tanaka and Mura model and Theory of the Critical Distance. For this purpose, the roughness of the rebars manufacturing process and the grain size variation of the steel were considered in the Tanaka and Mura model, which aims to calculate the number of cycles spent in the initiation phase. By combining the concepts of the Theory of the Critical Distance with the Paris Law, the calculation of the number of cycles for propagation was made taking into account microstructural and geometric aspects of the rebars. The fatigue life of the rebars was then calculated by adding the numbers of initiation and propagation cycles. The proposed approach was compared to experimental data from the literature and it has satisfactorily predicted the fatigue life of rebars.