The Earthquake Engineering Online Archive

Seismic performance of steel moment frames plastically designed by least squares stress fields

Ohi, Kenichi; Mahin, Stephen A.

UCB/EERC-89/08, Earthquake Engineering Research Center, University of California, Berkeley, 1989-07, 92 pages (555.1/O36/1989)

A new plastic design method is presented for moment-resisting frames which uses the lower bound theorem of limit analysis and a stress field termed the least squares stress field. Member forces are monitored at several points in a frame, and the sum of the squares of the moments is minimized among the member force distributions in equilibrium with the applied design load. The least squares pseudo-inverse technique is used to implement this procedure. Existing plastic design provisions for steel moment frames are reviewed, and two-story frame models with identical configurations are proportioned by the proposed design method considering load combinations specified by three different sets of design requirements used in the United States and Japan. Static and dynamic analyses are carried out on the model frames, and their seismic performances under a severe earthquake are compared.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-89-08.pdf (3 MB)