Column base connections under compression and biaxial moments : proposed design approach

Abstract

Very little guidance exists on the design of steel column base connections subjected to axial compression and biaxial bending. A new mechanical model is proposed here for designing such base connections. The model constructs the thrust-moment interaction curve of the connection, which can then be used for design. The method is aimed at unstiffened baseplates with four corner bolts, but may readily be extended to other layouts. The model makes several simplifying assumptions that reduces the problem to 3 modes of failure that employ simple geometric expressions and statics to calculate bolt and prying forces. Contrary to the Eurocode and AISC approach, the proposed model utilises the full plastic capacity of the plate under all loading conditions and on both the tension and compression sides of the connection. The resulting interaction curves were compared to experimental results from an experimental program of thirty-two tests to failure. The model predicts behaviour fairly accurately. It was also shown that the use of a linear moment interaction action equation is a conservative approach to designing base connections for axial force and biaxial bending.