Bending behaviour simulations of fibre reinforced beams with rebars by using the bridged crack model

The bridged crack model has been demonstrated to be an efficient numerical tool for investigating the behaviour of structural elements in bending. In the model, Linear Elastic Fracture Mechanics concepts are used to determine the equilibrium and the compatibility equations of a beam segment subjected to bending in presence of a mode I crack. Recently, the model has been extended to include the presence of closing stresses as a function of the crack opening in addition to steel reinforcement closing tractions. The ability of the model to analyse the mechanical behaviour of members having both steel and fibre reinforcements makes it a practical tool in structural design. In fact, it allows for studying the ratio of steel to fibre reinforcement percentages in order to optimise mechanical behaviour and costs. Some new techniques, recently proposed for reducing significantly the computing time in presence of cohesive stresses, are presented in the paper and an approximate criterion to account for concrete crushing is introduced as well.