||This study is to obtain the S-N curve of SD690 high-strength reinforcement. Therefore, the fatigue test is preformed to observe the fatigue behavior of RC beams with SD690 steel reinforcement. In the test, the cyclic fatigue loading, the mid-span deflection, concrete strain, the maximum width of concrete crack, and the compressive strain of top sectional concrete are measured for studying the fatigue characteristics of the New RC beams.|
The test results showed that the fatigue life of the higher strength reinforcement SD690 Bars can be predicted by the empirical equations proposed by the literature . The SD690 bar has the higher fatigue limit(fr, limit), and the better fatigue resistance than SD420 reinforcement.
The results also concluded that the stiffness of the New RC beams will decrease as the increase of the number of repeated fatigue loadings, especially in the about first one fifth of the fatigue cycles. That is, the reduction of RC beams stiffness is decreasing severely, and the width of flexural crack becomes wider as the number of repeated loadings increases. The final fatigue fracture locations of all the beam specimens were occurred at one of the top loading points. In addition, fracture area of the SD690 reinforcements is about 7% of total rebar sectional area, which is much smaller than the fatigue area of the SD420 reinforcement, about 50%.
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