This chapter is devoted to the analysis of statically determinate multispan beams and trusses, subjected to moving loads. Methods for the generation of beam and trusses, and the construction of influence lines are discussed. Different types of trusses are considered; among them are trusses with subdivided panels and some special types of trusses.

Multispan Statically Determinate Beams

Multispan hinged beams (Gerber–Semikolenov beams) are geometrically unchangeable and statically determinate structures consisting of a series of one-span beams with or without overhangs connected together by means of hinges. The simplest Gerber–Semikolenov beams are presented in Fig. 3.1.

Generation of Multispan Statically Determinate Hinged Beams

The following rules of distribution of hinges in beams, which have no clamped ends, provide their unchangeableness and statical determinacy:

1. Each span may contain no more than two hinges.

2. Spans with two hinges must alternate with spans without hinges.

3. Spans with one hinge may follow each other, providing that first (or last) span has no hinges.

4. One of support has to prevent movement in the horizontal direction.

Figure 3.2 shows some examples of the hinges distribution in beams without fixed ends.

The distinctive properties of multispan statically determinate beams:

 1. Structure with intermediate hinges has less stiffness than structure without intermediate hinges. This leads to substantial reduction of bending moments as compared with continuous beams spanning the same opening.

2. Possibility of control stresses by variation of hinges locations.

Advantages of multispan hinged beams are as follows:

1. Change of temperature, settlements of supports, imperfect of assembly does not create stresses.

2. Failure of one of the support may not destroy the entire system.

3. Relatively short members of multispan beams are well suited for prefabrication, transportation, and installation using standard equipment.

4. Multispan hinged beams are usually more economical than