Effect of Specimen Size and Initial Crack Location on Flexural Shear Behavior of UHPFRC

Abstract

Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) has outstanding post-cracking behavior which is explained by hardening part due to micro cracking and softening part of crack localization. Most UHPFRC structures are governed by concrete tensile behavior represented as critical crack localization, unlike ordinary reinforced concrete structures are designed to be governed by the yielding of steel reinforced rebar. In this research, crack localization characteristics of UHPFRC were investigated on three point bending test of twenty-four single notched prisms with varied types of location of notch, height of specimens and fiber volume ratio. The tensile fracture properties of UHPFRC were found out based on two parameter fracture model from the three point bending test results of center notched prism and direct tension test results of doubly notched plate. The structural implications of size effect in UHPFRC was examined by the fracture properties in terms of fracture process zone and specimen size. Within the height of 500 mm, size effect on flexural behavior was found only in structural ductility, not in the maximum strength. With respect to the location of notch, crack growth orientation were investigated and analyzed by maximum stress criteria. The results show that in-plane shear behavior of UHPFRC is much higher than ordinary concrete and it implies that the in-plane shear behavior of UHPFRC should be considered for designing structural elements.