Evolución hasta rotura de estructuras laminares de revolución de hormigón pretensado

Evolution up to failure of prestressed concrete axisymmetric shell structures

A numerical model for the nonlinear geometric and material analysis of reinforced and prestressed concrete axisymmetric shells is presented in this paper. The model is based on the displacement formulation of the Finite Element Method. The shell geometry is modelled by means of 3-nodes isoparametric shell elements. A layered system is used to represent the variation of the material properties through the thickness of the shell. A special purpose element to represent ring beams or edge elements of the shell is also presented. Concrete is assumed to be subjected to a biaxial state of stress in the shell and uniaxial longitudinal normal stresses in the ring-beams. Constitutive equations based on the nonlinear elasticity with unloading branches are used. Prestressing has been also accurately included in both aspects of geometry and structural effects. Two families of prestressing tendons are considered: meridional and circunferential tendons. Prestressing steel is assumed to have a multi-linear stress-strain relationship. Both pretensioned and postensioned can be included by means of the consideration of bond into the structural analysis proces. Two numerical examples are presented to show the capabilities of the developed numerical model. Example 1 illustrates a nonlinear material and geometric analysis of a reinforced concrete dome with a prestressed edge beam. Example 2 consists on a nonlinear analysis of a Nuclear Containment Vessell submitted to a inner normal pressure.