Lincoln Electric D1.8 - Manual (Page 4)

4 D1.8 Seismic Supplement Welding Manual
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Background
In January 1994, the Northridge, California earthquake caused unexpected damage to a number of welded
steel-framed buildings in the greater Los Angeles area. The Federal Emergency Management Agency (FEMA)
funded a variety of investigations that sought to address both the immediate and long-term needs related to
solving the performance problems associated with welded steel moment-frame connections. Several
documents were published as a result of these investigations, including Recommended Specifications and
Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications (FEMA 353)
1 .
FEMA 353 discusses what has come to be known as the “Pre-Northridge Connection” and concluded that
“…the typical moment-resisting connection detail employed in steel moment-frame construction prior to
the 1994 Northridge earthquake… had a number of features that rendered it inherently susceptible to brittle
fracture. These included the following:
The most severe stresses occurred in the connection
“Wildcat” welding position
Connection detail makes it hard to inspect
Significant flexural stresses on the beam flange at the column face
Weld access hole geometry
High restraint
Weak panel zones
The report continued on to say “…additional conditions contributed significantly to the vulnerability of
connections...” including:
Low toughness FCAW-S welding the consumables
Low redundancy
Matching beam and column strength
FEMA 353 then proposed a variety of recommendations and quality assurance guidelines that addressed
various topics, including:
Overall structural design
Connection design
Connection details
Materials, including both base metal and weld metal
Workmanship
Inspection