Finite element analysis model for reinforced concrete columns subjected to biaxial eccentric compression

To analyze reinforced concrete columns efficiently and accurately, a finite element model based on the fiber integration method for the material and geometrical nonlinear analysis of reinforced concrete columns with arbitrary section under biaxial eccentric compression was developed. On the basis of nonlinear stress-strain relationships of concrete and reinforced steel, a section analytical model suggested by Rodriguez was introduced to derive the section tangent stiffness matrix by directly integrating the trapezoids divided from the concrete section according to boundary vertices. The standard finite element formulae were established utilizing the nonlinear spatial frame element theory. The proposed model was used to calculate the ultimate load-carrying capacity of the reinforced concrete test columns subjected to biaxial eccentric compression. Analytical results show that the proposed model has higher computational precision, and that by adopting the fiber integration method instead of the conventional strip or square method, computational efficiency is improved notably.