Derivation of Key Characteristics of Columns in Frames with Sway

Abstract

The paper paper examines columns of elastic frames that are able to displace laterally under axial load. Columns on the same level (story) of such frames may contribute to lateral support (stability) or require lateral support (supported columns). In the former case, maximum moments will occur at column ends, but may occur between column ends in the latter case. The column response, including the formation of moments and shears, is often complicated, often calling for approximate analysis methods and information that presently may not be readily available. Main attention of the paper is paid to providing results that will be helpful in providing, in a rather simple manner, improved understanding of column mechanics, and that may be helpful also as a supplement to full second-order analyses. Towards this goal, the major objective of the paper is threefold: (i) to identify characteristic points, or behavioral“landmarks” in the axial load-moment solution space, through the study of rotationally restrained elastic columns and two-column panels with sidesway; (ii) to derive simple, novel, closed-form expressions for these, thereby providing a tool simplifying the establishment of the variation of end and maximum moments versus axial load; (iii) to identify to what extent isolated (single) column analyses may adequately represent horizontally interacting columns, and potential unwinding, in frames.