Moment Transfer at Column-Foundation Connections: Physical Tests

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, and anchoring to concrete. For any given connection, the strengths calculated with these three methods can differ by a wide margin. The application of these methods, including possible enhancements that improve strength estimates, is described. Laboratory tests were performed to provide benchmark physical data to determine the applicability of various design methods. The test specimens consisted of full-scale interior steel-column-to-concrete-foundation connections located away from foundation edges, with details typical of current construction practice on the West Coast of the United States. Strength in both tests was governed by concrete breakout failure. Strategically placed reinforcement increased the strength and displacement capacity of anchored connections governed by breakout. Design recommendations are provided. Keywords: anchoring to concrete; beam-column joint; breakout; column-foundation connections; shear reinforcement; strut-and-tie; supplementary reinforcement.