Shear resistance of prestressed HPFRC beams without stirrups: A mechanical analysis of shear-transfer actions based on detailed experimental measurements

Abstract

The use of High Performance Fibre-Reinforced Concrete (HPFRC with compressive strength up to 100 MPa) has shown to be a competitive alternative to conventional solutions for precast beams. This is justified by its affordable cost, high mechanical performance and enhanced durability. However, the shear response of such elements is still under scientific discussion and most design models provide scattered and highly conservative predictions, discouraging the use of HPFRC. In order to make a step forward in the understanding of such key aspect, this paper presents the results of an experimental investigation on eight full-scale HPFRC beams. The beams were tested with different levels of prestressing and were instrumented with refined optical DIC measurements. Using the experimental data, crack development and kinematics are investigated in detail, as well as the associated contributions of potential shear-transfer actions. The results confirm a significant contribution of the fibres in tension, as well as of the inclination of the compression chord for high levels of prestressing. The outcomes and failure modes of the different specimens are eventually compared and discussed, with the aim of setting the bases for more comprehensive and mechanically-based approaches for shear design of HPFRC.