Research on hexagonal concrete-filled steel tubular transition pieces for wind turbine hybrid towers under axial compression

With the escalating height of wind turbine structures, wind turbine steel-concrete hybrid towers have gradually become a new type of structure to replace pure steel towers. As a component connecting the upper steel tower with the lower concrete tower, the transition piece assumes an indispensable role in the overall structure of the hybrid tower. The traditional reinforced concrete-type transition piece has necessitated enhancements owing to the complicated construction and concrete cracking problems. A hexagonal concrete-filled double skin steel tubular (CFDST) transition piece is proposed to fit the hexagonal steel-concrete hybrid tower. Studies that investigate the hexagonal CFDST structures are currently few. Based on this, three hexagonal CFDST stub columns were tested, with the variables in stiffened measures. The experimental portion included a thorough investigation of local buckling behaviors and failure modes in addition to the analysis of typical mechanical indexes. Further, the validated finite element (FE) model was then utilized for mechanism analysis about the contact stress between different interfaces, the stress distributions, and so on. Besides, a parametric study was done to identify the sensitive parameters affecting this kind of structure's peak loads. Ultimately, the peak load prediction formulas found in published studies and specifications were modified by incorporating the findings from this investigation.