Flexural Fatigue-Life Distributions of Plain and Fibrous Concrete at Various Stress Levels

The paper presents results of an investigation carried out to study the fatigue life distribution of plain and steel fiber reinforced concrete with different fiber volume fractions and aspect ratios for various levels of the applied fatigue stress. An extensive experimental investigation was planned in which 210 flexural fatigue tests and 84 complementary static flexural tests were conducted on prismatic plain concrete and fibrous concrete specimens of 100×100×500mm size under three point loading in an MTS closed loop testing machine. Two types of crimped-type flat steel fibers with 25×2.0×0.6mm and 50×2.0×0.6mm, corresponding to fiber aspect ratios of 20 and 40, respectively, were used at each of the fiber volume fractions of 0, 1.0, 1.5, and 2.0%. It has been observed that the probabilistic distribution of fatigue life can be approximately modeled using the two-parameter Weibull distribution with statistical correlation coefficient exceeding 0.90. The shape parameter of the Weibull distribution for the fatigue life of concrete is different for different stress levels and fiber aspect ratios. The present study indicates that the probabilistic distribution of fatigue life of concrete depends on the level of applied fatigue stress, fiber volume fraction, and the aspect ratio of fibers. The graphical method, the method of moments, and the method of maximum likelihood estimation have been used to obtain the distribution parameters of the Weibull distribution. These three methods are shown to yield similar values of distribution parameters for the present fatigue data.