ABSTRACT
Beams have been used for many centuries but their systematic design had to await the development of a theory of bending. Structural elements which primarily resist bending are known as beams or girders, the former term being commonly applied to rolled sections and the latter to fabricated members. The range of choice of rolled beams is large and by the nature of their mass production they tend to be relatively cheap and widely available. The relatively slender profile of steel beams gives rise to a marked tendency to local or overall instability under certain conditions. Where steel beams support concrete slabs a reduction in steel beam weight is possible by interconnecting beam and slab. A complication which arises where a number of steel beams, relatively widely spaced, are composite with a concrete slab is that the elementary theory of beam bending, which assumes a constant stress across a beam at any horizontal level, may not be valid.
