The seismic stability and ductility of steel columns interacting with concrete footings

First-story columns in steel moment resisting frames are subjected to various forms of geometric instabilities during earthquakes. These instabilities have the potential to seriously compromise structural performance, and expedite structural collapse. In turn, these instabilities are influenced by the interactions of the column boundary conditions. Of specific concern are base connections that involve embedding the column into a concrete footing. These connections are nominally assumed to be fixed, although recent experimental data suggests that they could be significantly flexible. A finite element parametric study examining the effect of connection flexibility on interior column seismic performance is presented. Several key variables, including column base flexibility, cross-section, axial load, and column length are interrogated. Results of the finite element study are presented in support of developing quantitative relationships between column base conditions and deformation capacity of the columns. Incorporation of these relationships into modeling frameworks is discussed.