Plastic Design of Multistory Steel Frames by Computer

A method, implemented in a FORTRAN program, is developed for plastic design of both braced and unbraced multistory steel frames including a consideration of elastic stress and elastic deflection constraints. It is applicable to the design of rectangular multistory planar steel frames with coplanar loading. The method consists of three parts. The plastic analysis and design part follows a story-by-story optimization technique to determine a favorable force distribution in the frame in order to minimize steel cost. Member selection is in accordance with the 1969 AISC Manual of Steel Construction Specifications. An iterative design procedure is used to account for the P - Δ effect. The elastic analysis and elastic stress design part utilizes an exact matrix stiffness analysis and redesigns members to satisfy user imposed elastic stress constraints. Finally, the elastic stiffness design part follows a story-by-story optimization technique to redesign members in order to satisfy user imposed elastic lateral deflection constraints while minimizing steel cost increases. Example problems are presented which indicate the practicality of the design system.