Experimental investigation of continuous two-layer reinforced concrete beams

Models and full-scale statically determinate two-layer beams (TLBs) made of steel-fiber high-strength concrete (SFHSC) in the compression zone and normal-strength concrete (NSC) in the tensile zone have been tested by the authors. The present study is a further stage of these investigations, focused on testing a continuous, two-span TLB with optimal steel/fiber ratio as in the previous stages. This is the first experimental investigation of continuous TLBs (CTLBs). The study is aimed at testing the CTLB behavior under positive and negative bending moments in the span and above the middle support. An additional issue that is studied in the course of this work is the influence of bending moment redistribution on the behavior of a CTLB. As in the previous research stages, interaction of the concrete layers in a CTLB was studied to demonstrate the efficiency of such beams for real structures. No cracks between the SFHSC and NSC layers were observed up to the ultimate limit state of the tested beam, which demonstrates proper interaction between the layers. The results obtained in the present study enable the recommendation of CTLBs for practical application as effective and economical continuous bending elements.