The Earthquake Engineering Online Archive

Seismic behavior of multistory frames designed by different philosophies

Anderson, James C.; Bertero, Vitelmo V.

UCB/EERC-69/11, Earthquake Engineering Research Center, University of California, Berkeley, 1969-10, 196 pages (620.1/A52/1969)

This study examines the seismic behavior of unbraced, multistory steel frames proportioned using different design philosophies. Ten and 20-story, single-bay frames were designed by the following design philosophies: (1) conventional allowable stress, (2) strong column-weak girder, and (3) minimum weight. A digital computer is used to determine the nonlinear, dynamic response of the frames to strong ground motion. Since inelastic design methods are used, the following gravity load effects are considered in the analysis: (1) nodal forces due to gravity loads, (2) change in geometry (P-delta), (3) possibility of plastic hinges forming at midspan of the girder elements, (4) axial strain in the columns, (5) beam-column effect in the columns, and (6) axial flexural interaction in the determination of the plastic moment capacity of the columns. The moment-rotation relationship at the ends of the beam and column elements is assumed to be bilinear. The geometry of this relationship can be altered by varying the yield moment and rate of strain hardening. To evaluate the efficiency of the three designs, the following response characteristics are considered: maximum displacement, maximum story to story displacement, time history of plastic rotation at each plastic hinge, time history of any selected story displacement, maximum variation of axial force, girder ductility ratio, and column ductility ratio. The ductility requirements are defined in terms of the curvature ductility. Energy data are used to draw some very general conclusions regarding the seismic behavior.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-69-11.pdf (7 MB)