Second-order FE Analysis of Axial Loaded Concrete Members According to Eurocode 2

Abstract: A nonlinear finite element analysis was performed for an axial loaded reinforced concrete column subjected to biaxial bending taking into account second-order effects. According to Eurocode there are two ways to take second-order effects into consideration: nonlinear FE analysis and hand calculation based on the simplified methods explained in Eurocode 2. Since simulating this kind of structures in ABAQUS is difficult, several simulations were made to find the correct model with satisfying accuracy. The nonlinear analysis focused on material modelling of concrete and its nonlinear behaviour. The simulation took into consideration the inelastic behaviour of concrete along with the confinement effect from transverse reinforcement. The finite element model was verified by comparing the obtained results from FEA to the results from a benchmark experiment. The mean values needed for simulating the FE model was derived from the mean compressive strength of concrete. After verification, another FE model using design parameters was analysed and the results were compared to the results from calculations based on simplified methods according to Eurocode 2 to see how much they agreed with each other. In a parametric study, the effect of eccentricity, compressive and tensile strength of concrete, fracture energy, modulus of elasticity, column cross-section dimension and length, steel yield stress and stirrup spacing were studied. A comparison between outcomes from the simplified methods and ABAQUS, calculated with design parameters showed that the bearing capacity from FE analysis was 21-34 % higher than the one obtained with the simplified methods. It is recommended that in further studies, analyse different slender reinforced concrete column with different L/h with FE-simulation to investigate if FEA always gives a more accurate result. For this case, and probably for columns with complex geometries, a finite element analysis is a better choice.