Experimental analysis of the shear behaviour of prestressed and reinforced concrete beams

This paper presents the detailed experimental results of 23 full-scale rectangular and I-shaped prestressed and reinforced concrete beams. All beams were designed to fail in shear and were subjected to a four-point bending test with monotonically increasing load until failure. The main investigated parameters were the amount of prestressing, the amount of longitudinal and shear reinforcement ratio and the shear span-to-effective depth ratio respectively. An extensive set of displacement and deformation data were gathered during the experiments using both traditional mechanical measurement devices and advanced optical(-numerical) measurement techniques. The experimentally measured failure loads are compared to analytical predictions obtained from current Eurocode 2 shear design equations. In general, a poor correlation was found between the reported experimental results and analytical predictions (mean experimental to predicted failure load ratio equal to 1.77; coefficient of variation equal to 31.6%). Based on the measured deformation fields, it was observed that, in the case of rectangular beams and prestressed I-shaped beams with shear reinforcement, the applied load is primarily carried by means of a direct compression strut which significantly increased the failure load.