Steel Reinforcement Ratio Dependency of Plastic Rotational Capacity of Reinforced Concrete Beams

This paper describes experimental observations intended to verify the dependency of plastic rotational capacity on steel reinforcement ratio. Variable parameters are: scale, steel ratio and slenderness. Experimental results are obtained varying the percentage of reinforcement and beam dimensions to analyze the structural response for a practical construction. These beams are normally designed in such a way that the internal forces as well as their distribution over the transversal section are calculated using the elastic beam theory, while the beam dimensions are designed using the ultimate limit state. Reinforced concrete beams must be designed to have a ductile response. This is necessary to guarantee the structural safety and internal forces redistribution during their life. In fracture mechanics, it is seen that beams with higher dimensions are brittle, while those with small dimensions are ductile. So, it is important to clarify whether the same material and design concepts can be applied for reinforced concrete beams with different dimensions. The influence of size and steel ratio on the inelastic rotational capacity has not been completely clarified and demonstrated yet. In fact, the experimental data available up to a few years ago, mostly obtained by load-controlled tests on reinforced concrete beams with high ductility bars, show a considerable scatter. On the other hand, some numerical evaluations, assuming strain localization in the compression zone, indicate that plastic rotation depends on the steel ratio and scale (beam depth), and the experimental tests recently carried out seem to validate this dependence.