A Plastic Method For Unbraced Frame Design

Abstract

Frequently, because of architectural or functional requirements, no structural bracing can be permitted in the plane of a multi-story frame. Furthermore, with the trend in modern building design towards light curtain wall construction, larger window areas, and removable interior partitions, the bracing effect provided by cladding is often small or unreliable. Because of this situation the designer is faced with the design of an unbraced multi-story frame in which the bare structural skeleton of columns and girders must resist all applied gravity and lateral loads. Certain initial steps in the design of unbraced frames are identical to the same steps in braced frame design. For example, the dimensional layouts in both designs, being based on architectural and functional requirements, will likely be similar. The assignment of load systems and their distribution to the plane frame will be the same. The working loads will also be increased by the same load factors in each design.