In this paper the efficiency of Branson’s equivalent inertia to consider the physical nonlinearity of beams in simple form is evaluated. For this purpose, several reinforced concrete plane frames of medium height are analyzed using ANSYS software. Initially, the frames are processed considering both physical and geometric nonlinearities. Next, geometric nonlinear analyses are performed, considering a physical nonlinearity approximated through the stiffness reduction in the structural elements. In the case of the columns, the stiffness was reduced by 20% and, for the beams, the inertia reduction values according to the Branson [1] formula and the NBR 6118:2007 [2] Brazilian Norm were used. It was observed that the inertia reduction according to the Branson [1] formula better represents the actual behavior of the structures at the service limit state. Furthermore, it was verified that the use of Branson’s equivalent inertia is more efficient at representing the behavior of the more flexible frames than stiffer frames.
reinforced concrete; physical nonlinearity; Branson’s equivalent inertia