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Chapter 2.3 Cantilevers

Cantilevers are a useful and often dramatic expression of structural form. In simple terms they are fixed at the support so as to limit or eliminate rotation and free at the end. The fixed end exhibits greater flexure and the free end greater deformation when compared the mid-span point of an equivalent span simply supported beam. The basic principles are examined followed by an exploration of the effects of the addition of a back-span. The concluding part shows how cantilevers may be used in real structures; with methods of achieving architectural expression.

Figure 2.3.2 Cantilever Beam Principles
What distinguishes a fixed end cantilever from a simply supported beam? It has a free end. The supported end is held up but, unlike the simple support, the beam cannot rotate. Figure 2.3.2 shows that it would not work as a cantilever if the supported end could rotate.
Figure 2.3.5 Cantilever with Backspan

‘To an engineer cantilevers provide a challenge with increased shear, bending and deflections at the support compared with simply supported structures.’ A common error which newly employed graduates fall into is to underestimate the deflections of beams which comprise a simply supported condition with an overhang (generally termed cantilever with backspan).

Demonstration Spreadsheets

The following figures are available to download in MS Excel format.