Low Cyclic Load Behavior of Reinforced Concrete Beams

Abstract

In the present scenario, the design of concrete structure needs accurate knowledge on the behavior of concrete. Information is available on the static load behavioral condition of concrete but limited information on the cyclic loading of concrete. The objective of the study is to examine the cyclic loading behavior of reinforced concrete beams. The present study has focused on investigating the effect of cyclic loading on the failure mode of reinforced concrete beam under bending. The cyclic loading of concrete was achieved by loading-unloading-reloading, for a short duration, in a specific stress range and for a few numbers of cycles. The experimental investigation included testing of six reinforced concrete beams. All beams have equal dimensions and length. The only variable was the ratio of web reinforcement. Four of the specimens were tested under a cyclic loading, at the stress range of 0 to 92 % of the yield loading and ultimate load for few numbers of cycles then loaded till failure. The remaining specimen was tested under monotonic loading till failure. The results of cyclic loading tests were compared with the beam tested under monotonically loaded. The mode of failure for Test Beam-1, which is loaded under cyclic loading in a single side, and Test Beam-4, which tested under cyclic loading and monotonically for reverse side was investigated. The shear cracks occurred before the yielding of longitudinal reinforcement. This is different from expected mode of failure which shows the cyclic loading change the mode of failure of the beam. While checking Test Beam-2 and Test Beam-3, the beams failure were due to yielding of longitudinal reinforcement followed by concrete crushing as expected. The result of this test shows that up to 15% of flexural to shear capacity ratio, the mode of failure of the beams in this experimental result were changed. It was recommended that follow up study on high cyclic loading, and low cyclic loading for deep beam, pre-stressed beam and composite beam should be done to validate the overall results.