The influence of joint details and axial force ratios on failure mechanisms of SCFT column-beam connections

Abstract

Three types of joint detailing are suggested in Chinese specifications to reinforce CFT column-steel beam connections, including internal diaphragms (ID), external diaphragms (ED) and through diaphragms (TD). Previous research has mainly focused on a single type of connection detail; very little comparative research has been conducted on the differences of these details in influencing the behavior of the connections. Full-scale experimental research and finite element analyses (Abaqus) are conducted to study the effect of joint details and axial force ratios on the failure mechanisms of CFT column-steel beam connections. Force transfer mechanisms and shear deformations of the joint are further investigated using advanced computational models. The results show that the connections with reinforcement details suggested by Chinese specifications provide satisfactory seismic performance. ED connections exhibit the highest shear strength and lowest ductility. ID connections provide the highest ductility and lower shear strength. TD connections exhibit similar performances as ID connections. The comparison of these connections shows that connection type, diaphragm thickness and tube thickness have a significant influence on the joint confinement and may lead to different failure mechanisms of the connections. A high axial force ratio may also cause an undesirable column yielding mechanism if the reinforcement of the joint is inadequate.