A SPREAD PLASTICITY FLEXURE- SHEAR INELASTIC FINITE ELEMENT FOR THE STUDY OF RC STRUCTURES

capable to model the flexure-shear interaction both in terms of stiffness, strength and residual ductility. The objective is not the definition of an itemized model, rather an accurate model with a sustainable computational cost for the seismic vulnerability analysis of existing buildings. Especially for non slender structures, the contribution to the nonlinear behaviour due to flexure may be not sufficient and flexure-shear interaction changes deeply the structural response. This new finite element is based on the adoption of Heaviside s distributions functions to model abrupt, both flexural and shear, stiffness discontinuities of the beam, by which it is possible to lead to the exact closed-form solution of the Timoshenko beam differential equations. The new frame element is composed by two sectional constitutive models, one for flexure and one for shear, that can interact by means of an empirical relation that relates curvature demand and shear strength degradation. The flexure shear model is verified against experimental tests on RC rectangular columns, walls and frames. Comparisons with experimental results on these shear-sensitive elements shows relatively good agreement.