Optimum plastic design of tapered gable frames

This study deals with the problem of plastic analysis and design of symmetrical tapered or uniform gable frames of the portal type subject to usual loads. In the course of this study, a fully automatic plastic design procedure, based on an original conversational computer program written by H. B. Harrison, was developed and implemented on the UNIVAC 1108 computer. Input data was made free-format in order to eliminate the inconvenience present in using a fixed-format input. Another new feature of the program is the capability of dealing with tapered-column gable frames. The procedure for analysis and design in the modified program accounts for the strength reduction in the plastic moment capacity caused by the presence of axial thrust in the frame members. The program also checks for the limiting width-to-thickness ratios of web and flange as given by the 1971 AISC specifications which serve to prevent local buckling failures.