Effect of embedment length of tension reinforcement on the behavior of lightweight concrete deep beams

Tests were carried out on 24 lightweight concrete deep beams to study how their behavior was affected in the ultimate load range by the embedment lengths lor the end-anchorage of the main tension reinforcement. In deep beams, the applied load is transferred to the supports mainly through the compression struts in a truss/arch mechanism. Hence, the main reinforcement has to act as a tension tie, and therefore, requires adequate end-anchorage. Additionally, the compression strut and the support reaction will act together to produce a transverse or normal pressure that may increase the bond strength and thus, the anchorage strength of the main tension reinforcement. This favorable effect, which has been reported by other researchers, may reduce the required embedment length for end-anchorage of the tension reinforcement. In the tests, as the embedment length of the tension reinforcement is reduced, the ultimate behavior of the beams is critically observed in the light of current ACI and other design recommendations for deep beams. To the authors' knowledge, the research described in this paper represents the first direct attempt to validate the favorable effect of normal pressure on bond strength in deep beams.