TABLE OF CONTENTS In Chapter 1 we discussed various structural forms and saw that for moderately large spans, simple beams become uneconomical and may be replaced by trusses. These structures comprise members connected at their ends and are constructed in a variety of arrangements. In general, trusses are lighter, stronger and stiffer than solid beams of the same span; they do, however, take up more room and are more expensive to fabricate.
Initially in this chapter we shall discuss types of truss, their function and the idealization of a truss into a form amenable to analysis. Subsequently, we shall investigate the criterion which indicates the degree of their statical determinacy, examine the action of the members of a truss in supporting loads and, finally, examine methods of analysis of both plane and space trusses.
Generally the form selected for a truss depends upon the purpose for which it is required. Examples of different types of truss are shown in Fig. 4.1(a) (f); some are named after the railway engineers who invented them.
For example, the Pratt, Howe, Warren and K trusses would be used to support bridge decks and large-span roofing systems (the Howe truss is no longer used for reasons we shall discuss in Section 4.5) whereas the Fink truss would be used to support gable- ended roofs. The Bowstring truss is somewhat of a special case in that if the upper chord members are arranged such that the joints lie on...
