Toward Earthquake-Resistant Design of Concentrically Braced Steel-Frame Structures
1 Introduction
1.1 BACKGROUND
The 1994 Northridge earthquake produced unanticipated damage in special steel momentresisting frame (SMRF) buildings (FEMA 2000a).
Although no SMRF buildings collapsed, damage
found in these buildings resulted in significant economic
losses. One aspect of this damage was particularly alarming to many
structural engineers, who had anticipated that welded steel
beam-to-column
connections were capable of undergoing large plastic
rotations, on the order of 2% or more.
In many SMRF buildings, quasi-brittle fractures had
developed in and around the welded joints connecting the beam
flanges to the columns. In several cases, these fractures
had spread into the adjacent column and panel zone region.
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