Fatigue behavior of steel reinforced concrete (SRC) beams with different shear span-to-depth ratios

There is an increase in the use of steel reinforced concrete (SRC) beams in high-speed railway platforms and bridges that are subjected to fatigue loading. It was found by the authors in their previous research on SRC beams under fatigue loading that flexural fatigue failure was the dominating failure mode when a large shear span-to-beam depth ratio (λ) of 2.63 was used. Research on reinforced concrete (RC) beams under fatigue loading and research on SRC beams under static loading revealed that shear failure may dominate when the shear span-to-beam depth ratio gets smaller. It is unknown if shear fatigue failure will happen in SRC beams with smaller shear span-to-beam depth ratio. This paper presents an experimental investigation of fatigue behavior of SRC beams with shear span-to-beam depth ratio of 1.8, 1.5, 1.1 and 1.0. It was found that shear fatigue failure did not occur in all twenty-seven SRC beams tested even for λ ratio as low as 1.0. Because the failure mode is found to be the same (i.e. dominated by flexural fatigue failure) for all the SRC beams with λ ranging from 1.0 to 2.63, the test results of all 39 SRC beams under fatigue loading were grouped together to derive fatigue strength curves for SRC beam design.