Load transfer mechanism in concrete-filled steel tubular columns: Developments, challenges and opportunities

This article provides an in-depth review on the understanding of load transfer mechanism in concrete-filled steel tubular (CFST) columns, with emphasis on tube-concrete interface behaviour, secondly, load transfer to encased concrete by bond strength, and lastly, load transfer by blind-bolt bearing. This article summarizes the diverse observations on obtaining a reliable bond strength between infill concrete and steel tube of CFSTs, as this is the key component that ensures the load transfer from the beam to the column. After assessing the bond strength, the identification of the zone for load introduction from fin-plate connection to CFST column is pertinent, as it is assumed to occur through bond strength via an introduction length, and studies on this aspect have been reviewed in detail. The review further extends to understanding of load transfer through bearing mechanism of blind-bolts, and provides an overview of the current developments in blind-bolted connections, which might overcome some of the challenges related to uncertainties in load transfer through bond strength. The article aims to highlight the authors' reflections on exploring and connecting the above-stated three sub-topics related to load transfer in CFST columns, discussing the challenges, and concludes by presenting the avenues for futue research.