Low damage steel base connections

Abstract

Base connections link column to ground and essentially provide a building fixation to the foundation to the foundation. Seismic damage to these connections can significantly raise repair cost and the risk of demolition if costs are too high. This thesis explores the experimental and analytical studies on performance of steel column base connections under seismic demands to develop low damage base connections. Tested base connections include exposed base plate connections with and without anchor rod preloading, bases with different patterns of asymmetric friction connections, and bases with yielding angles. Analytical studies are used to quantify the effect of base flexibility on structural demands. The overall goal is to develop low damage base connections. The experimental results indicate that the proposed details for base connections with friction connections provide repeatable cycles without strength degradation or any requirements for repair or replacement following an earthquake. However, some stiffness degradation was observed, particularly after cycles on axially loaded specimens in the weak axis direction. In addition, the construction details of these connections are practical for construction and can be easily detailed by engineers. Comparing the performance of tested base connections shows that if low strength loss is important, then bases with friction connections are rational selections. If simple detailing and construction is a top priority, then bases with yielding angles are potentially better choice. Finally, exposed base plate connections provide more stiffness for connections expected to have lower rotational demands. Initial rotational stiffness can be set for all connection types by changing the design and detailing parameters for the specific connection, making them customizable for design. Macro models of these base connections were developed or modified to enable design of these base connections by practitioners. These models are critical as they enable the translation of this research into industries and direct practices. Thus, they are a final link between the experimental results, new designs and potential new construction.