Experimental investigations on flexural fatigue strength and crack growth in plain concrete beam with notch or unnotch were conducted by means of four-points bending test method. These tests were carried out under the following condition, a) size of concrete beam ; 75×75×300 mm, b) single edge notch beam with relative notch depth ; 0.12 constant, c) cyclic load at 5 Hz, d) repeated maximum load rates ; 0.8, 0.75, 0.7 and 0.65, e) load amplitude ; 0.1, 0.25, 0.5 and 0.75. According to test results, the conclusions were obtained as follows ; 1) flexural fatigue strength in notched beam can be explained by equation of S_<max>=0.839-0.052・logN_f, 2) flexural fatigue strength of notched beam is about 10 % smaller than one of the unnotched beam, 3) in range of strain softening zone, Paris' low can be applied for concrete, 4) material constant, m in Paris' low showed by (da/dN)=C(Δk)^m, is 4.2〜4.9 for concrete.
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