Size effect on post-cracking strength of high performance fibre-reinforced concrete

Abstract

The size effect is a well-known phenomenon in the design of reinforced concrete structures. Although it has been studied extensively for conventional concrete with or without traditional reinforcement, its influence on the post-cracking behaviour of fibre-reinforced composites is scarcely reported in literature. This is particularly true in the case of high performance fibre-reinforced concrete (HPFRC), which allows the design of very thin elements and whose behaviour may be highly influenced by their size. The aim of this research was to evaluate the influence of the size of HPFRC beams on the mechanical performance at a cross-sectional level. An experimental program involving three-point bending tests of HPFRC on beams of dimensions 40 40 160, 100 100 400 and 150 150 600 mm was conducted. Three steel fibre contents were investigated: 90, 140 and 190 kg/m3 . These bending tests were also simulated via a sectional analysis model, taking as a reference the constitutive law described in the fib Model Code for Concrete Structures 2010. The results suggest that the values of stress in the constitutive model should depend upon the cross-sectional size of the beam. This is reflected when adjusting the parameters of the MC2010 to fit the experimental values, resulting in a coefficient of determination above 0.88 when comparing the ratio between these two parameters and the size of the cross section.