Simplified Solution to Interaction Equation

Abstract

According to the requirements of the AISC Specification, there are three equations, Formulas (1.6 1a), (1.6-1b), and (1.6-2), which must be considered in designing a steel column subjected to combined loading. In Formula (1.6-1a), the combined axial and bending stress is limited by stability, while yielding controls the combined stress in Formula (1.6- b). This factor is appropriately known as the amplification factor. The computed bending stress is required to be increased due to the additional bending stress induced by a secondary moment. This moment is caused by the compressive force and the deflection of the column due to moments applied at the ends and/or a transverse loading on the column. The purpose of this paper is to facilitate the calculations required for obtaining the modified bending amplification factor along with the allowable bending stresses of various steels available. It is hoped that with the use of the proposed charts, the time and effort of the designer will be greatly reduced.