Analysis of a more ductile connection between steel beams and concrete-filled tube columns

Abstract

To resolve the problem of ductile fracturing of beam flanges in traditional connections with concrete-filled steel tube columns using site-welded side plates, an alternative connection design requiring minimal site welding was designed and studied. An explicit analysis method, considering the fracture strain criterion developed by the stress triaxiality path, was adopted to study the seismic performance and fracture resistance of the proposed connection. The results of a verified finite-element model indicated that the steel beam flange in the connection never fractured. The connection exhibited a notably higher maximum bending moment and ductility than the traditional connection. The side plates in the proposed connection were tension-bending or compression-bending elements, unlike in the traditional connection. The failure modes, maximum bending moment, ductility and stress distribution of the side plates were compared and analysed parametrically. Based on the stress distribution of the side plates according to the finite-element results, a fitting formula related to the width and thickness of the side plates was obtained. A formula to calculate the flexural capacity was also developed according to the force model of the proposed connection. The calculations and finite-element results were in good agreement.