Kristof De Wilder

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.

Experimental failure analysis of shear-critical ordinary and steel-fibre prestressed concrete beams using optical measurement techniques

Although the use of fibre reinforced concrete (FRC) for structural applications is continuously increasing, it is still limited with respect to its potentials. This can be mainly attributed to the lack of international building codes for FRC structural elements. This paper aims to contribute to the development of suitable design principles for shear in FRC elements by presenting the preliminary results of 6 full-scale pretensioned steel-fibre reinforced concrete members. The main investigated parameters are the amount of prestressing, the amount of shear reinforcement and the fibre dosage respectively. All specimens are subjected to a four-point bending test until failure. Traditional mechanical measurement devices are used in combination with advanced optical measurement systems (i.e. stereo-vision digital image correlation 3D DIC and Bragg grated optical fibres). Apart from the full-scale tests, a number of small-scale experimental investigations are performed to characterize the material properties. The experimentally determined results are compared to predictions using analytical models found in Eurocode 2 (EC2) and Model Code 2010 (MC2010). Based on the obtained full-field data from the DIC systems and the detailed deformation information obtained from the Bragg grated optical fibres, an assessment is made of the mechanical behaviour.