Capacity of exposed column base connections subjected to uniaxial and biaxial bending moments

Current guidelines do not address the design of column base connections under combined biaxial bending moment and axial load. An analytical study is conducted to develop a biaxial moment-axial load interaction curve for design of exposed, unstiffened column base plates. First, a 3D finite element analysis model is developed for these connections. The response of the model is validated through a series of existing experimental data. Next, the model is used to investigate the response of a few connections subjected to various biaxial moments and axial loads. Based on simulation results, a simple and reasonably accurate interaction equation is proposed. Since the uniaxial capacities of the connection are involved in the interaction curve, an analytical method for predicting the uniaxial capacities, is also presented. This analytical method, which is based on formation of plastic mechanisms, is able to predict the strength of flexible base plates with high accuracy. The behavior of exposed base plates with I-shaped columns under minor-axis moments is also studied. Findings of this study assists practitioners with a reliable and convenient column base connection design.