The Earthquake Engineering Online Archive

Behavior of pre-Northridge moment resisting steel connections

Yang, Tzong-Shuoh; Popov, Egor P.

UCB/EERC-95/08, Earthquake Engineering Research Center, University of California, Berkeley, 1995-08, 55 pages (517.5/Y26/1995)

The basic reasons for the fractures that occurred in steel moment-resisting connections during the 1994 Northridge, California, earthquake are examined from a fundamental point of view. This examination begins with a discussion of material properties, and calls attention to the shortcomings of the conventional tension tests. The stress-strain diagrams for specimens having a circular groove around the specimen (resembling a condition at the critical weld at a connection) are entirely different, exhibiting a brittle fracture compared with a ductile response for a bar of constant cross-section. The misleading ASTM requirement for minimum strength with no specified maximum results in a melee of actual strengths in use of which the designer is unaware. This prevailing condition makes it impossible to design rationally. The possible modes of failure are examined, showing the very limited view in the code design. Then, a simplified and more accurate analysis of a beam-column connection is examined. Based on the above background, three SAC pre-Northridge specimen tests subjected to cyclic loadings are critically examined.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-95-08.pdf (3 MB)