Behavior and design of column base connections

This dissertation investigates the design and behavior of column base plate connections, a common structural component used to transfer forces from the steel superstructure to the supporting concrete foundation. Laboratory testing and damage reported in recent earthquakes has demonstrated the susceptibility of these connections to various failure modes. However, compared to other structural connections, column bases have received relatively limited research attention.;In order to characterize the connection behavior, results from two series of large-scale testing are presented. The first phase of testing investigates common base connection shear transfer mechanisms, including plate friction, anchor rod bearing and shear key bearing. The second phase of testing investigates the response of exposed bases subjected to axial compression and flexural loading. The test observations are complimented by detailed test analyses and FEM simulations.;A detailed review of existing design provisions, design guides and published research reveals that current approaches to characterize the behavior of exposed column base connections loaded in shear or a combination of axial compression and flexure are not well developed nor supported by adequate experimental validation. Thus, the test data is used to evaluate existing approaches and propose refinements. For example, the tests investigating shear key bearing indicate that current strength design provisions may be significantly unconservative for large foundations due to the size effect in concrete.;Furthermore, an evaluation of experimental data indicates that the current design methods for flexural loading may be highly conservative with respect to the ultimate strength of the connection. A design approach is proposed in which the ultimate strength of the connection is governed by the formation of a plastic mechanism. All test specimens show outstanding ductility, suggesting that reliable inelastic action is possible for base plate connections. Additional methods, which are based on the concept of the center-of-rotation of the base plate, are proposed to characterize the anchor rod forces and the initial moment-rotation behavior. The proposed behavior predictions are highly accurate with respect to the test data. The dissertation concludes with a detailed overview of current design provisions along with analysis and recommendations for design.