Behavior of Reinforced Concrete Structures Subjected to Biaxial Excitation

The nonlinear behavior of reinforced concrete columns under biaxial excitation is complicated by a variety of factors. A finite‐element model is presented for the analysis of such members under generalized biaxial loading. The formulation accounts for most aspects of axial‐flexural behavior and is capable of handling numerically ill‐conditioned problems associated with softening behavior. The element formulation is initially outlined and the ability of the element to predict experimental data is demonstrated. Numerical simulations are presented of cantilever columns under static load and of an entire frame in bidirectional seismic excitation. The results demonstrate the complexity of the biaxial resistance mechanism and its influence on structural response, particularly related to the concentration of local damage in columns.