FE model for physical and geometrical nonlinear analysis of three dimensional frames of reinforced concrete buildings
Elisabeth Junges1; Henriette Lebre La Rovere2
1 Departamento de Engenharia Civil - Universidade Federal do Espírito Santo (DEC-UFES); 2 Departamento de Engenharia Civil - Universidade Federal de Santa Catarina (ECV-UFSC)
doi:10.20906/CPS/CILAMCE2017-0485
Resumo
This paper presents a refined model for analysis of reinforced concrete (RC) spatial frames and building frames, taking into account both material and geometric nonlinearities. The 3D model is based on the finite element method (FEM) and it is implemented into a computer program called ANEST/CA. The structures are discretized using 3-node bar finite elements, by neglecting shear deformation in the bar element formulation. The material nonlinearity is considered along the element length and over the element section area, which is divided into filaments, by assuming that each filament is under a uniaxial stress-state. Nonlinear constitutive laws based on stress-strain relationships are used for both concrete and reinforcement filaments. A refined tension-stiffening model is considered for concrete and a bi-linear stress-strain law is adopted for the reinforcing steel. Torsion is considered decoupled from the other internal forces, and a trilinear constitutive model is adopted to represent the torsional stiffness of the element. The geometric nonlinearity follows the Total Lagrangean Formulation. To simulate the effect of high in-plane stiffness of the floor slabs on the building structural behaviour, rigid diaphragms constraints can be considered in the modelling. The ANEST/CA program is validated by comparison with experimental tests on reinforced concrete structures, and also by comparing its results with the ones from CONS program (Marí, 2000). Only two examples of such comparisons were selected for this work, one RC plane frame and a small RC 3D one-floor building. Results from the analyses show that ANEST/CA program is indeed capable of reproducing the complete nonlinear structural behaviour of RC building structures.
Palavras-chave: Nonlinear analysis; 3D frames; Reinforced concrete; Finite elements