Flexural fatigue strength and failure probability of steel fibrous concrete

This paper presents a study on the fatigue strength of steel fibre reinforced concrete (SFRC) for various stress levels. An experimental program was conducted to obtain the fatigue lives of SFRC at various stress levels. Forty four beam specimens of size 500 mm × 100 mm × 100 mm were tested under four-point flexural fatigue loading. Thirty six complimentary static flexural tests were also conducted to obtain the static flexural strength of SFRC prior to fatigue testing. The specimens incorporated 0.5% volume fraction of corrugated xerox type steel fibres of size 0.6 mm × 2.0 mm × 30 mm. All the fatigue tests were conducted on 100 kN MTS close loop electrohydraulic servo-controlled universal testing machine. The number of cycles to failure of the specimens at different loading conditions were noted as fatigue life N from the cycle counter of the machine. Flexural fatigue life data thus obtained was analyzed in an attempt to determine the relationship for SFRC between stress level S, number of cycles to failure N and probability of failure Pf. It was found that this relationship can be represented reasonably welt graphically. A family of S-N-Pfcurves were obtained. The experimental coefficients a, b and c of equation L = 10-a(S)b(log N)c were determined from the fatigue test data obtained in this investigation to present the S-N-Pf relationship analytically.