Ultimate Strength of Multistory Steel Rigid Frames

Load displacement relationships of large plane multistory steel rigid frames have not been investigated extensively. A numerical technique for the elasticplastic analysis of rigid frames was developed and programmed. The obtained computer program was used to analyze five 10-story, two-bay and five 32-story, three-bay frames which had been designed for realistic office building loading in accordance with current allowable stress design procedures. The analyses, which accounted for the effects of joint displacements, spreading of yielded zones, and residual cooling stresses, showed that frames became unstable before the formation of a mechanism and that frame stability was mainly a function of frame girders rather than columns. For these frames use of Julian-Lawrence Alignment Chart for column design was shown not to offer any advantages over the use of K=one, while the assumption regarding fixity at the base was shown to be an important design consideration.