An alternative method for the calculation of instantaneous deflection in reinforced concrete beams

Abstract

A method for the calculation of instantaneous deflections for reinforced concrete beams is presented in this paper. This method is based on the tension stiffening principles of the CEB-FIP Model Code 90. The abverage behaviour of a section of the beam is represented by means of an average cracked inertia, according to the Model Code 90, in a similar way to the method used by Favre. By means of the corresponding integration by curvatures along the beam, deflection at midspan is obtained, and accordingly, an equivalent inertia, representing the global behaviour of the beam is defined. With this equivalent inertia the instantanous deflection at midspan can be calculated for each loading state. Unlike Branson's method, this equivalente inertia is obtained from ain interpolation of inverses of the gross and the cracked section inertias, at the sections ends and midspan sections of the beam.