Behavior of Square Hollow Section column connection using Thread-anchored One-side Bolt under tensile force at high temperature

Abstract

A series of tests including 30 specimens were conducted to study the tensile performance of Thread-anchored One-side Bolted (TOB) Square Hollow Section (SHS) column connections at high temperature. Ambient temperature test was conducted firstly to acquire basic tensile behavior of the TOB bolted SHS column connection. Then both steady-state fire test and transient-state fire test were carried out on the basis of ambient temperature test. Four typical failure modes of TOB bolted SHS column connection were observed in test. The thickness of the SHS column wall, the bolt diameter and thickness of the T-stub flange had obvious influence on the failure mode of TOB bolted SHS column connection. But the change of temperature or applied load had negligible impact on the failure mode. The hole threads could provide reliable anchorage to TOB before the yielding of the connection, which demonstrated the reliability of the novel TOB at different temperatures. The fire temperature and the load ratio had great influence of the tensile resistance of connection at high temperature. Test on connections bolted by Traditional High-strength Bolt (THB) were also conducted for comparison. Result showed the tensile behavior of TOB connection was comparable to THB connection at high temperature when the failure mode of the connection was T-stub flange yielding with bolt failure. Equations for predicting the failure mode and resistance of TOB bolted connections at high temperature were proposed. Accuracy of the design equations were validated with the test result. The equations could judge the failure mode precisely and predict the yielding load with enough accuracy.