ABSTRACT
This study evaluates and compares the seismic performance of the older steel moment frames with partially restrained (PR) connections. Typical 4-, 6-, and 8-story older frames were designed based on the 1952 AISC code using the “Wind Moment Frame” method. Nonlinear time-history analyses were conducted for thirty Mid-America ground motions using a modified version of the DRAIN–2DX program. The primary performance indices used were connection rotations, interstory drift angles (ISDA), panel zone deformations, and plastic hinge rotations. The performance of these frames are evaluated in accordance with FEMA 273 and 356 criteria for the central USA, a region of large but infrequent seismic events. The results show that these frames may be susceptible to serious damage if subjected to a large earthquake (2% in 50 years) if the frames were designed for wind forces only. However, the existing structures would perform reasonably well for a moderate event (10% in 50 years).
