Types of loads External loads on a structure may be classified in several different ways. In one classification, they may be considered as static or dynamic. 1. Static loads are forces that are applied slowly and then remain nearly constant. 2. One example is the weight, or dead load, of a floor or roof system. 3. Dynamic loads vary with…
The arches are widely used in modern engineering. Arches permit to cover a larger span. The greater is the span than an arch becomes more economical than a truss. From aesthetic point of view the arches are more attractive than trusses. Materials of the modern arches are concrete, steel, and wood. The body of the…
The following trusses are considered in this section: Three-hinged trusses, trusses with a hinged chain, and complex trusses. Each of the above-mentioned trusses has some peculiarities. Three-Hinged Trusses A three-hinged truss is actually two trusses connected by the hinge C as shown in Fig. 3.20a. Both supports are pinned. The fundamental feature of this structure…
The Baltimore truss is widely used in bridge-building for cases involving particularly long spans and large loads. The classical Baltimore truss is a Pratt truss strengthened by two additional members in each panel (members 2-4 and 3-4 in Fig. 3.16a). The modified Baltimore truss is a Pratt truss strengthened by three additional members in each…
Trusses with subdivided panels present are simple trusses with additional members. Figure 3.15a shows the Pratt truss with two additional members within each panel; for first panel they are 3-k and k-n. Figure 3.15b shows the Parker truss with three additional members within each panel; they are a-b, a-c and b-c. In both examples additional…
The trusses according to their generation are subdivided into simple, compound, and complex ones. Simple Trusses Simple trusses are formed on the basis of a hinge-connected triangle with any additional joint attached by means of two additional members. The relationship between the number of bars (S) and joints (J ) for simple statically determined and…
For construction of influence lines of reactions and internal forces for statically determinate multispan beams the following steps are recommended: Step 1. The entire multispan hinged beam should be presented in the interaction diagram form. This helps to classify each element of the structure as primary or secondary beams, and visualize the load path from the…
Gerber–Semikolenov beams may be schematically presented in the form, which shows the interaction of separate parts and transmission of forces from one part of the beam to another. Gerber–Semikolenov beams consist of two types of beams, namely a main (or primary) and suspended (or secondary) beam. A main beam is designed to carry a load,…
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…
So far, we have been considering cases when external loads were applied directly to the beams. In practice, however, loads are often applied to secondary beams (or stringers) and then are transmitted through them to the main beam (or girder) as shown in Fig. 2.15. Stringers are simply supported beams. Each stringer’s span is called…