Analysis of Slender Reinforced Concrete Columns based on a Nonlinear Mixed Formulation with Analytical Interpolation Functions

Resumo

The design of concrete columns requires two main steps: global and local analysis. Generally, the global analysis is performed using a simplified model considering the gz coefficient with a stiffness reduction of the structural elements to simulate the nonlinear behavior. In contrast, the local analysis demands a more rigorous process, particularly for slender columns. Typically, column analysis usually is conducted using the Finite Element Method, with appropriate discretization to accurately capture the nonlinear behavior and effects P-D and P-d. In this context, the local modelling of columns using a mixed element formulation with analytical interpolation functions can avoid the need for intense discretization while effectively capturing the curvature along the element. This study proposes a design methodology for slender and very slender reinforced concrete columns based on a mixed element formulation, which employs analytical interpolation functions to approximate displacements and internal forces and uses a corotational total Lagrangian description. The P-D and P-d effects are naturally considered in this approach. The proposed numerical application clearly demonstrates the capacity of the formulation to simulate the nonlinear local analysis of reinforced concrete columns using just one element and to accurately capture the curvature and bending moments along the column in the design process.