Repeated and Reversed Loading in Reinforced Concrete

Three beams tested at the Univ. of Ill. during 1959-61 were subjected to reversal in the direction of loading and 18 others were subjected to repeated loading in one direction. The behavior of the three beams subjected to reversal of loading is discussed in detail. The reduction in stiffness of a reinforced concrete beam with progressive damage resulting from repeated loading is examined. The three beams with reversal of loading were found to possess load-deflection capability similar to that for companion beams not subjected to reversal of loading. Envelope curves for companion beams show this comparison. Ultimate moment for the beams subjected to reversal of loading was found to be practically unaffected by the previous reversal of load in these tests. Some loss in ductility was observed, but large plastic rotation capacity was observed in all of these beams which were doubly reinforced.