Prediction of mean and design fatigue lives of steel fibrous concrete beams in flexure

The paper presents results of an investigation carried out to study the flexural fatigue strength of steel fibre reinforced concrete (SFRC). An experimental investigation was planned in which 180 SFRC beam specimens of size 100 x 100 x 500 mm were tested under four-point flexural fatigue loading. The specimen incorporated three different volume fractions i.e. 1.0%, 1.5% and 2.0% of corrugated steel fibres. Each volume fraction incorporated mixed steel fibres of size 0.6 x 2.0 x 25 mm and 0.6 x 2.0 x 50 mm in different proportions. The fatigue-life distributions of SFRC at a given stress level, is shown to approximately follow the two-parameter Weibull distribution. The parameters of the Weibull distribution for fatigue life of SFRC have been obtained from S - N relationships. Mean and design fatigue lives have been obtained for SFRC with different fibre volume fractions, each volume fraction containing different fibre mix proportions. It has been observed that SFRC having 1.0% fibre content with fibre mix proportion of 35% 50 mm + 65% 25 turn long fibres exhibits the highest mean and design fatigue lives.