Prediction of flexural fatigue strength of steel fibrous concrete using Weibull distribution

This paper presents a study on the fatigue strength of steel fibre reinforced concrete (SFRC) for various stress levels and stress ratios using two-parameter Weibull distribution. An experimental programme was planned to obtain the fatigue lives of SFRC at various stress levels and stress ratios. Eighty three SFRC beam specimens of size 100 mm x 100 mm x 500 mm were tested under four-point flexural fatigue loading. Sixty eight complementary static flexural tests were also conducted. The specimens incorporated 0.5% volume fraction of corrugated xerox type steel fibres of size 0.6 mm x 2.0 mm x 30 mm. Concept of equivalent fatigue-life, reported for plain concrete in literature, is extended to SFRC to incorporate the effects of stress level, stress ratio and survival probability (reliability) using the fatigue equation S = fmax/fr = A(N)-B(1-R). The results indicate that the distribution of equivalent fatigue-life is in excellent agreement with the two-parameter Weibull distribution. The coefficients A and B of this equation have been obtained corresponding to different survival probabilities so that the equation can be used to predict the flexural fatigue strength of steel fibrous concrete.