J. P. Ulfkjær

Post cracking behavior of lightly reinforced concrete beams

The main object of the research work presented in this paper is to establish design tools for lightly reinforced flexural concrete members subjected to bending load. An analytical model for predicting the load deflection curve is established and compared with experimental results. The main focus will be minimum reinforcement requirements and the related size effects. The main idea of the analytical model is to assume that the response of the structure can be described by the cracking response located within a fracture band. Outside the fracture band Bernoulli-Euler beam theory is assumed. The constitutive model for the concrete is based on the idea that the initial part of the stress crack width relation can be described by a linear relation between load and crack width, taking into account the stresses caused by aggregate interlocking. The model follows ideas previously used by other researchers in order to describe the fracture mechanics of concrete beams. These ideas are extended in this model to take into account the pullout of the reinforcement.