Tensile Behavior of UHPFRC under Uniaxial and Biaxial Stress Conditions

Representative and accurate characterization of the tensile behavior of strain hardening Ultra High Performance Fiber Reinforced Cementitious Composite (UHPFRC) remain a challenge. Currently, the uniaxial methods, like direct tensile test (DTT) and 4-point bending test (4PBT), are commonly applied, although the biaxial tensile condition has been widely recognized in the UHPFRC applications, e.g. thin UHPFRC layers as external reinforcement for RC slabs. In this paper, results from ring-on-ring testing of circular slab-like specimens are presented to determine the equi-biaxial tensile response by means of inverse analysis using 3D finite element method (FEM). In addition, DTT, using structural specimens cut from large square plates, and 4PBT, using standard specimens cast in mould individually, were carried out. The tensile response from 4PBT was derived through inverse analysis using 2D FEM. Finally, the corresponding results from the three different testing methods under either uniaxial or biaxial stress condition were analyzed and compared in terms of tensile characteristic parameters, tensile material law, fracture process, and energy absorption capacity. While the three testing methods did not show significant difference in tensile strength, significantly higher strain hard-ening deformation was identified in the case of biaxial stress conditions.