New mechanism of load introduction into concrete-filled steel tubular column

This paper presents the results of new load-introduction tests and numerical simulations to investigate the mechanism of load introduction from shear connections to concrete-filled steel tubular (CFST) columns, and the effectiveness of changing different construction details. The results of the tests have confirmed the authors’ recently proposed new load introduction mechanism, obtained from an extensive numerical study. In the new load introduction mechanism, the connection load is introduced to the concrete core via the column length above and within the connection or the cap plate on top of the column. There is no limit to the load introduction length above the connection. Below the connection, there is transfer of forces from the steel tube to the concrete core, but the total force in the column remains unchanged. This load introduction mechanism is different from that assumed in the various current design codes, including Eurocode 4 and AISC Specification. This study has an important implication on CFST column design: using shear connectors below the connection is ineffective in increasing CFST column strength.