Hysteretic Behavior of RC Beams

A mechanical model for the cross section of a reinforced concrete beam is proposed. Attention is focused on the local phenomena relating to the cross section, while the phenomena relating to the beam element to which the section belongs is ignored. In particular the concrete fracturing mechanism and the slippage and yielding of steel are considered, while the smeared damage of concrete are not taken explicitly into account. Namely, a rigid‐plastic constitutive law is assumed for steel, while for concrete a linear elastic one. Loading and unloading processes are considered, the bending moment range being lower than that of crack extension. The phenomenon of shake‐down due to slippage or plastic deformation of the steel bars is studied. Up to a certain value of the bending moment an elastic shake‐down occurs; above this value the shakedown becomes elastic‐plastic and an hysteretic loop is described by the stressstrain diagram of steel. Thus the energy absorbed in such a dissipative phenomenon is computed for each loading cycle and some experimental results are reviewed.