Probability of fatigue failure of steel fibrous concrete

The paper presents a study on the fatigue strength of steel fibre reinforced concrete (SFRC) at various stress levels. To obtain the fatigue lives of SFRC at various stress levels beam specimens of size 500 mm X 100 mm X 100 mm were tested under four-point flexural fatigue loading. Static flexural tests were also carried out to determine the static flexural strength of SFRC prior to fatigue testing. The specimen incorporated three volume fractions, namely 0(.)5, 1(.)0 and 1(.)5% of corrugated steel fibres of size 0(.)6 mm X 2(.)0 mm X 30 mm. All the fatigue tests were conducted on a 100 W closed-loop universal testing machine. Fatigue life data thus obtained were analysed in an attempt to determine the relationship for SFRC between stress level S, number of cycles to failure N and probability of failure P-f for SFRC. It was found that this relationship can be represented reasonably well graphically by a family of S-N-P-f curves for SFRC containing different volume fractions of fibres. The experimental coefficients of the equation were determined from the fatigue test data to represent the S-N-P-f relationships analytically.