The static loading tetsts and the fatigue tests have been carried out on various kinds of concrete beams be means of a electro hydraulic fatigue testing mechine
with suwomechanism, which has a capacity of 50 tons for dynamic loading and 75 tons for static loading. The testing beams provided with double reinforcement were
2.8 m in length, 20 cm in width and 31 cm in height. The longitudinal reinforcement ratio, concrete strength and the amount of web reinforcements were varied.
　The results obtained from the fatigue tests are as follows;
　(1) Under dynamic loading,shear failure sometimes occurs before flexural failure. The fatigue strength of shear failure is considerably smaller than that of flexural failure.
　(2) The fatigue strength of flexural failure depends upon concrete sterngth σc and stell ratio p. It is satisfactory to consider the allowable stress of reinf　orcement as 1,800kg/cm2 in the case of reinforcement
　σsy=3,500kg/cm2.
　(3) The maximum crack width under dynamic loading is roughly two times as wide as that under static loading.