ABSTRACT
After a few years of successful application of the fiber beam element to the analysis of reinforced concrete structures, the introduction of the mechanisms of shear deformation and strength appears to be as the necessary further step towards a realistic description of the ultimate behaviour of shear sensitive structures. The basic idea is to model the shear mechanism at each concrete fiber of a cross-section, assuming the strain field of the section as given by the superposition of the classical plane section hypothesis for the longitudinal strain field with a uniform distribution over the cross-section for the shear strain field. Transverse strains instead, are internal variables determined by imposing the equilibrium, separately at each fiber, between the concrete and the vertical steel reinforcement. Since transverse strains components are not known in advance, and because of the non linear behaviour of the concrete and the steel, an iterative procedure is needed to find the equilibrium in the transverse direction. In the paper the new approach to the shear modelling in nonlinear fiber beam elements is presented and the practical application to a 2D section is illustrated.
