A 3D mixed frame element with multi-axial couplingfor thin-walled structures with damage
Journal Title: Frattura ed Integrità Strutturale - Year 2014, Vol 8, Issue 29
Abstract
A 3D mixed beam finite element is presented, modeling the warping of the cross-sections as anindependent kinematic field. The beam formulation is derived on the basis of the Hu-Washizu variationalprinciple, expressed as function of four independent fields: the standard displacements, strains and stresses andthe additional warping displacement. This is interpolated along the beam axis and on the cross-section, byplacing on it a regular grid of interpolation points and adopting Lagrange polynomials. The warping degrees offreedom defined at the cross-section interpolation points are condensed, thus preserving the element matrix andvector sizes. A fiber discretization of the cross-sections is adopted. The constitutive relationship at the midpointof each fiber is based on an isotropic damage model for brittle-like materials, distinguishing between the damagevariables in tension and in compression to properly describe the unilateral effect. An efficient algorithm isformulated for the element state determination, based on a consistent linearization of the governing equations.A simple numerical application on a cantilever beam with torsion in the linear elastic range is presented and twotorsion tests on plain concrete beams are performed, by comparing the numerical results with the experimentaloutcomes.
Authors and Affiliations
D. Addessi, P. Di Re
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