Influence of cyclic loading on corrosion-fatigue life of concrete bridges superstructure

Abstract

The planned high-speed railway line Moscow – Saint-Petersburg makes high demands on the reliability and durability of artificial structures in its composition. The service life of the main load-bearing structures of bridges is prescribed by design standards at the level of 100 years, while there is no possibility of its justification and calculation confirmation. Operating experience allows us to conclude that single structures on existing railway lines reach such a period without reconstruction or major repairs. This article discusses corrosion-fatigue durability as one of the aspects of the method for predicting the service life of a bridge, taking into account the dynamic load. This type of degradation of reinforced concrete is caused by the combined action of pitting corrosion of reinforcement and cyclic loading, which leads to the initiation and growth of a fatigue crack in the reinforcing bar. A method for calculating the time of crack growth from its inception to a critical value is given. The methodology includes modeling and dynamic calculation of a reinforced concrete frame span of a bridge, processing the bending moment spectrum and extracting the average stress value and the number of its repetitions, modeling crack growth using the principles of fracture mechanics. Trains A1-A10 were analyzed along SP 453 in the speed range from 120 to 400 km/h. The values of the fatigue crack growth time for the selected trains and speeds, which cause the largest range of stresses in the reinforcement, are obtained.