Prediction of fatigue lives for steel beams and steel reinforced concrete beams

With the wide application of steel reinforced concrete (SRC) beams, the problem of fatigue has become increasingly prominent. To deeply understand the fatigue performance of SRC beams, a finite element analysis (FEA) about fatigue failure process of SRC beams was performed. The internal H-steel inside SRC beam (SRCH-steel) was shown to possess similar fatigue failure characteristics to steel beam and exert a deciding influence on the fatigue resistance of SRC beam in previous experiments. Therefore, FEA of fatigue crack growth (FCG) was conducted using a fully-automated remeshing technique for steel beam first. Comparisons were made and a good agreement was found between predicted and experimental fatigue lives. The average value of ratio between predicted and experimental fatigue lives for the five steel beams is 1.149, which verifies the accuracy of FEA model. Then, based on the FEA model of steel beam, rebars and external concrete were included to simulate fatigue failure process of SRC beams. The results suggest that the average value of ratio between predicted and experimental fatigue lives for SRCH-steels inside the thirty-nine SRC beams is 1.191, and the average value for tensile rebars is 1.212, which indicates that the numerical model is accurate and reliable. At last, further analysis about influences of critical parameters on fatigue performance of SRC beams was conducted, such as nominal stress range, steel ratio of SRCH-steel, steel ratio of tensile rebars, fatigue strength of tensile rebars, shear span-to-depth ratio, concrete strength grade and stirrup ratio.