UC Berkeley

Steel and precast columns are commonly designed to transfer moment loads to concrete foundations through cast-in-place headed anchors. In design office practice in the United States, connection strength has been evaluated considering mechanisms emphasizing joint shear, strut-and-tie modeling, or anchoring-to-concrete. For any given connection, the strengths calculated with these three methods can differ by a wide margin. The breakout failure mode is not routinely checked, even though recent physical tests have shown it can limit connection strength. Strategically placed shear reinforcing bars have been shown to increase the strength and displacement capacity of anchored connections governed by breakout failure. However, designers cannot consider the beneficial influence of shear reinforcement on breakout failure as it is generally ignored by current building codes (for example, ACI 318-19 and Eurocode EN 1992-4). Through physical testing and finite element simulations, this dissertation investigates the application of various design methods, including possible enhancements that improve strength estimates. A novel approach to calculating the concrete breakout strength with distributed shear reinforcement is proposed. This dissertation is divided into three sections: (i) a description of observations from physical tests that consisted of full-scale interior steel-column to concrete-foundation connections with details typical of current construction practice on the West Coast of the United States, (ii) a description of how physical test data are used to calibrate finite element models of column-foundation connections to investigate critical variables, and (iii) a discussion of a novel approach to calculating the concrete breakout strength considering the additive effect of concrete and reinforcing bars when distributed shear reinforcement is present.