Un modelo unificado de resistencia a flexión y cortante de vigas esbeltas de hormigón armado bajo cargas puntuales y repartidas

A mechanical model is presented for shear-flexural strength of slender reinforced concrete beams under concentrated or distributed loads. The model incorporates the shear transferred by the un-cracked concrete head, by the cracked web and by the longitudinal and transverse reinforcements. Failure is assumed to occur at the un-cracked concrete zone, subjected to a biaxial stress state, when the Kupfer failure envelope is reached and the stirrups are yielded. A general procedure and simplified direct design equations are derived taking into account equilibrium and a given stress distribution at ultimate limit states (ULS). The model predictions have been compared with the results of more than 1300 tests performed on simply supported beams, having obtained very good agreement. Because of the simplicity, accuracy, and the physical insight of the problem provided by the model, it may be very useful for rational performance-based design of concrete structures in practice.