AN OPTIMAL NUMERICAL MODEL FOR NONLINEAR BEHAVIOR OF REINFORCED CONCRETE FRAMES

This paper is a review of a possibility for numerical modeling of in-plane reinforced concrete (RC) frames loaded by various loadings. Research scope is limited only to beam/column frame structures without wall/plate structural elements. The objective of this research is a formulation of an enough sophisticated and, for civil engineering design purposes – “optimal” i.e. reasonably convenient numerical model. Structural discretization and mathematical approximations are based on the finite element method (FEM) concept. For modeling concrete and steel nonlinear behavior uniaxial constitutive rules for these materials are used. The steel-concrete bond relation is modeled indirectly – by tension stiffening effect. As opposed to standard one-dimensional “1D” beam FE models, that includes only the concrete and reinforcement behavior modeling, the suggested two-dimensional “2D” beam FE model includes the interaction of shear and flexural forces. The proposed model is based on “2D” beam FE with capabilities of sophisticated models. The introduced numerical concept for simulation of structural behavior of RC frames loaded by various loads (from simple static to complex cyclic) is formulated as a compromise solution. The compromise is made between accuracy, as an essential parameter, and, on the other hand, simplicity, as everyday design practice task. The objective of presented research was to find the “middle way” (synchronized accuracy and numerical efficiency) in nonlinear analyses of the described RC frame structures.