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Chapter 2.4 Continuous Beams

Figure 2.4.10 Continuous Beam Moment Redistribution

Add one internal support – or more- to a simply supported beam and the resolution of forces becomes statically indeterminate. In the spans the beam becomes stiffer than its simply supported counterpart. The beam bends over the supports (hogs) in an inverted form of the simply supported moment. The chapter follows with: a brief examination of two and three equal span continuous beams; a review of continuous unequal spans; the effects of asymmetric loading and differing adjacent beam stiffness; a useful method of adding a hinge in the spans to achieve statical determinacy; redistribution of moments from support to internal spans and the elastic shear effect in frames.

Many built structures are continuous; in particular steel and concrete framed structures.  Design methods for concrete frames are mostly based on continuity – in beams and slabs – taking advantage of fixed connections by placing additional reinforcement over posts and columns. A process of redistribution is often carried out in concrete framed building for continuous beams. This is a way of creating a more even arrangement of reinforcement.

Demonstration Spreadsheets

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