Experimental study on prefabricated CFST Columns with bolt-coupler baseplate connections under compression

This paper investigates the structural behaviour of prefabricated concrete-filled steel tubular columns (CFST) with bolt-coupler baseplate (BCB) connections under compression experimentally. BCB connection is an innovative solution that simplifies the construction process and reduces costs. Experimental investigations were conducted on 10 column specimens (5 stub columns and 5 slender columns) to understand the effectiveness of BCB connections used in prefabricated CFST (PCFST) columns to transfer the load of the upper column to the lower column. Four CFST columns without connection and six PCFST with BCB connections were prepared. Results showed that prefabricated CFST stub columns with BCB connections achieved comparable or slightly higher (≈1.4%) load-carrying capacity than CFST columns without connections. For CFST slender columns with BCB connections, the 87 % increase in height compared to the stub columns resulted in a slightly lower load-carrying capacity (≈1.5%) than that of CFST columns without connections. The ultimate compressive strength of the proposed prefabricated CFST columns, along with 19 previously reported tests with various connections, was used to evaluate the predictive accuracy of the existing design codes (EC4 and AS 2327). Findings indicated that the connection type significantly impacts design strength and that must be considered. Cost analysis confirmed that BCB connections are more economical than splice plate blind bolted connections (by 77 %) and conventional precast RC column connections (by 65 %), validating the proposed system's superior structural performance and cost-effectiveness.