Qualitative Analysis and Design

Abstract

Before embarking on a full analysis of a structure, it is often useful to have an idea of what the final result should look like. Qualitative analysis can give you the general form of the nsm-diagrams without actually performing an analysis, that is, without going through the calculations that provide the values of the internal forces or reactions. For complex structures under complicated loading this may be easier said than done. But our aim is also didactic. It will assist us in performing and especially understanding the results of a real analysis. We will be mainly concerned with redundant beams and with some elementary frame examples. The method is to a large extent visual, and it uses an holistic approach in the sense that we employ everything we know about structural analysis, especially equilibrium, in order to improve the approximate result we are working on. The key to performing a qualitative analysis is Hooke’s law for a beam element in bending $m=(EI)\;\kappa$, where EI is considered constant.