Bidirectional Behaviour of Unstiffened and Stiffened Direct-Welded Connections for Square CFST Columns

Abstract

This paper describes finite element analyses of two-way moment frame beam-column joint subassemblies constructed using steel I-shaped beams connected to square concrete filled steel tubular (CFST) columns. These are direct-welded connections with (i) no stiffeners, (ii) internal horizontal stiffener plates, (iii) vertical tube stiffeners, and (iv) the combination of (ii) and (iii). They were analyzed under one-way and two-way column lateral loading. It is shown that internal stiffeners increase the joint stiffness and strength by up to 80% and 60% respectively. The effect of bidirectional loading on the joint capacity is found to be minor. A design method is developed to predict the required stiffener capacity. The method is applicable for both one-way and two-way loading cases.