Numerical simulation of the behavior of axially loaded reinforced concrete columns

Abstract

A nonlinear finite element procedure has been developed for the simulation of the behavior of axially loaded reinforced concrete columns. The concrete constitutive law is carefully calibrated for the range of stress-strain state that is of interest in column analysis. The smeared crack approach in concrete cracking modeling is then modified to suit the nonlinear stress-strain law. Application of the finite element procedure to spirally reinforced concrete columns produces results that provide a clear plcture of the interaction between the confining hoops and concrete core. The sequence of events that leads to the peaking of the load-carrying capacity of the column and the eventual decrease of the load carrying capacity are also identified. A preliminary result based on a linear elastic analysis is also obtained for a square concrete column reinforced with rectilinear ties. The result reveals potential cracking zones that are consistent with those found in laboratory tests. The longitudinal reinforcing bar in a concrete column is analyzed with a special bar element for the inelastic buckling behavior. The post-yield buckling path is traced beyond the peak load. It is found that the axial load-carrying capacity of a high strength steel bar can be computed from the inelastic material law directly without considering the effect of post-yield buckling if the bar is supported laterally with a spacing less than seven times the bar diameter.