Nonlinear numerical analysis of a concrete frame under corrosion due to carbonatation

Resumo

Reinforced concrete structures are used worldwide due to their durability, resistance and flexibility to
conform to different geometries. However, exposure to weather causes degradation, and pathological
manifestations may appear. One of the most common is corrosion, their be generated by chloride ingress and
carbonation. In the initiation stage, the corrosion agents cause depassivation of the rebar. Afterwards, the
propagation stage begins, where the structures suffer loss of rebar area, cracks, strength loss and, in the end,
collapse. In this paper, the displacements evaluation of a structure under carbonation was accomplished by
implementing the loss of rebar area. Through the coupling of the reduction of the stiffness of the structure in the
propagation stage with the Finite Element Method based on Positions code dedicated to the analysis of laminated
frames, developed in FORTRAN programming language, that naturally considers geometric nonlinearities,
allowing high displacements and rotations, and using Saint-Venant-Kirchhoff’s constitutive law. FEM based on
Positions uses total Lagrangian formulation and its degrees of freedom for frame elements are given by nodal
positions and generalized vectors which may express the variation of section heigh and rotations. The physical
nonlinearity of concrete was considered by implementing Mazars damage model. The results have shown that the
numerical model is efficient to simulate the degradation of structures under uniform corrosion.