Failure Analysis of Welded Steel Moment-Resisting Frame Connections

Full-scale welded steel moment-resisting frame (WSMF) connections have been tested to failure at the University of Michigan and at Lehigh University. The tests were conducted at ambient temperature and under a simulated seismic loading protocol developed by the SAC Joint Venture, to determine if newly detailed unreinforced fully restrained post-Northridge connections can behave satisfactorily in future earthquakes. This paper presents a failure analysis of 16 full-scale WSMF connections. The effects of weld-access hole geometry and the roughness of its flame-cut surface are analyzed. The analysis describes the initiation and propagation of fatigue cracks at intersections of the weld access hole with the beam flange and from the flame-cut surface of the weld access hole in the WSMF connections. The paper suggests changes to the weld access hole, and the surface roughness for the flame-cut surface of the weld access hole, which would improve the performance of unreinforced post-Northridge WSMF connections subjected to seismic loads. ©2002 American Society of Civil Engineers