Analytical behaviour of CFDST chord to CHS brace composite K-joints

Concrete filled double-skin steel tubular (CFDST) members have been adopted as electrical poles in China and are having increasing utilization in trusses, bridges and lattice structures. Besides previous research work on the structural performance of individual CFDST components and the experimental results on CFDST joints reported by the authors in the companion paper (Hou and Han, 2016), up until now there is little understanding on the detailed analytical behaviour of typical connections formed by such composite members. This paper thus presents a finite element analysis (FEA) on composite K-joints formed by CFDST chords and circular hollow section (CHS) braces. The FEA modelling was validated by the reported test data and then used to perform analysis on multiple types of possible failure modes, full-range load-deformation relations, and material interactions along the cross-sections of such new type of composite joints. Comparative analysis and parametric analysis was also performed, based on which simplified formulae for calculating the strength of CFDST K-joints were presented and validated.