Flexural strength of prestressed Ultra-High-Performance concrete beams

Abstract

This paper attempts to develop a design approach for determining the flexural strength of prestressed ultra-high-performance concrete (UHPC) beams. For this purpose, a numerical analytical model was firstly proposed for the moment–curvature of prestressed UHPC sections. To validate the developed analytical model, a flexure test was conducted on a full-scale pretensioned UHPC girder with an overall depth of 900 mm. Based on the validated model, a parametric study was then conducted to evaluate the crack localization, the fiber contribution, and the size effect with respect to the flexural strength. It was found that the peak moment of the crack localization-controlled section was reached when the tensile strains in steel strands approximately reached their yield strains. The crack-bridging fibers in UHPC contributed significantly to the flexural capacity of the prestressed UHPC sections with relatively low reinforcement ratios. There was a clear size effect in the flexural strength of prestressed UHPC sections. For the rectangular section with a flexural reinforcement ratio of 1 %, a 10.5 % reduction in the normalized flexural strength was observed, as the beam height increases from 500 to 2500 mm. Finally, a flexural design approach for prestressed UHPC sections considering the fiber contribution as well as the size effect was proposed. The proposed approach was verified by comparing the experimental results of flexural tests on prestressed UHPC beams performed by the authors and others to the analytical predictions.