LRFD Beam-Column Graphical Design Aid

Abstract

A graphical design aid is presented for beam-columns, members subjected to combined loading of axial forces and bending moments, designed in accordance with the American Institute of Steel Construction's (AISC) 1993 LRFD Specification for Structural Steel Buildings. Design aids have been published in the AISC LRFD Manual of Steel Construction, 2nd Edition, addressing many facets of structural steel design. These include the beam tables, beam charts, and column tables. However, meager information is available revealing how to design a beam-column accurately and quickly. The common method is entirely based on an assumed axial load due to bending moments which is then used via trial-and-error to size a member from the column (axial load only) design tables. There are various problems with this method of design. This article presents an alternative design procedure based on the Equations H1-1a and H1-1b of the 1993 LRFD Specification for Structural Steel Buildings. The proposed design method consists of a standard set of graphs depicting the interaction diagram for steel W-shapes commonly used as column members. The diagrams are derived for structural members subjected to axial compression and strong axis bending. This new procedure also utilizes a set of linear transformation factors applied to design conditions different from the graphical standard. This method is advantageous to design engineers because it facilitates the selection of a beam-column.