Column base plates under biaxial bending moment and axial force

Abstract

This paper deals with an extensive finite element parametric study on exposed column base plates subjected to the combination of biaxial bending moment and axial force. The objective is to explore the effect of the connection geometry as well as loading conditions on the resistance and rotational stiffness of the base-plate connection. The influence of the base plate thickness, anchor bolt diameter, column cross section (I or H section), bending moment orientation and axial force magnitude is investigated in details using a numerical model that has been previously validated based on experimental tests performed by the authors. A particular attention is dedicated to the contact pressure distribution and the M-N interaction curves. Analytical models are proposed to evaluate the in-plane, out-of-plane and biaxial bending resistances considering the contribution of an axial force. Both the contribution of the column web and the size of the compression area depend on the base-plate thickness and are accounted for in the evaluation of the in-plane bending resistance. For out-of-plane bending resistance, a parabolic M-N interaction curve is derived. The biaxial bending resistance is evaluated considering the plastic redistribution of out-of-plane bending moments between the right and the left sides of the column base plate (with respect to the strong axis). A simplified method is also proposed to determine the resistance whatever the orientation of the bending moment and the axial force.