Potential Errors in Approximate Methods of Structural Analysis

A recurring procedural flaw exists in many textbook treatments of approximate methods for the analysis of rectangular, rigid frames under uniform vertical loading. The majority of textbooks surveyed cite an inappropriate assumption regarding the approximate analysis of vertically loaded frames which leads to erroneous solutions. One of the prevalent assumptions, which leads to incorrect shear forces and bending moments in columns, is that a negligible axial force exists in each girder. A more appropriate first-pass substitute might be to assume that inflection points occur in each column at mid-height, or at hinged supports of column bases at ground level. Using a simple, uniformly loaded, symmetric, rectangular frame as an example (this frame appears frequently in textbook examples), a trial revised set of assumptions produces an improved approximate solution. Work is proceeding to develop a fully tested, revised method of approximate structural analysis for vertically loaded rectangular frames.