Identification of Constitutive Relationships for Fibre Reinforced Concretes by Inverse Analysis

The present paper describes the results of an inverse analysis procedure for the determination of the parameters of constitutive relationships for fibre reinforced concretes. The behaviour of cracked beams in three-point bending was studied using a cracked hinge model [1]; the basic idea of which is to divide the portion of the beam close to the propagating crack in a series horizontal strips, attached at the ends to two rigid boundaries which can translate and rotate. The strips are modelled as independent spring elements with nonlinear constitutive behaviour and are used to model the evolution of a fictitious crack [2]. The data used as input for the inverse analysis was obtained from an experimental campaign that investigated the performances of concrete specimens fibre reinforced with either steel or macro-synthetic fibres under three-point bending [3]. Good accuracy of the simulated results for all the specimens subjected to testing has been obtained. In particular, the stress-crack opening relations calibrated by the adopted procedure, give force-CMOD (Crack-Mouth-Opening-Displacement) diagrams in good agreement with the experimental diagrams in terms of all the quantities considered in the optimization process.