Numerical performance of blind-bolted demountable square CFST K-joints

A demountable connection is an effective solution to separate and reuse steel or composite components after their first-stage design life, and could therefore benefit the environment by reducing material consumption and saving natural resources. Blind bolts and through-bolts are usually served as connectors in such demountable connections to replace traditional welding works. This paper puts forward a novel design on demountable square concrete-filled steel tubular (CFST) K-joints fabricated with concrete filled chord, hollow braces, flush endplate, blind bolts and through-wall bolts. Advanced finite element analysis models of the novel joints were established using verified modelling techniques. Among the investigated flush endplate designs and bolt arrangements, it is found that the design with through-bolt anchored beneath the tensile brace and a continuous flush endplate has advantages in material efficiency, joint strength and limiting endplate-chord separation, and is therefore chosen as the prototype design. Analysis on the failure modes shows that brace buckling failure prevents premature failure of the other members and ensures the safety as well as reusability of the main composite chord. Furthermore, discussions on the strength prediction based on numerical analysis and parametric study on key factors such as flush endplate thickness and brace-chord width ratio are given.

Automated summary

This paper introduces a novel design for demountable square concrete-filled steel tubular (CFST) K-joints, which use blind bolts and through-wall bolts as connectors to separate and reuse steel or composite components effectively. Research indicates that among various flush endplate designs and bolt arrangements, a design with through-bolt anchored beneath the tensile brace and a continuous flush endplate has advantages in material efficiency, joint strength and limiting endplate-chord separation.