OVERVIEW

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The general structural theory presented in Sec. 3 can be used to analyze practically all types of structural steel framing. For some frequently used complex framing, however, a specific adaptation of the general theory often expedites the analysis. In some cases, for example, formulas for reactions can be derived from the general theory. Then the general theory is no longer needed for an analysis. In some other cases, where use of the general theory is required, specific methods can be developed to simplify analysis.

This section presents some of the more important specific formulas and methods for complex framing. Usually, several alternative methods are available, but space does not permit their inclusion. The methods given in the following were chosen for their general utility when analysis will not be carried out with a computer.

4.1 THREE-HINGED ARCHES

An arch is a beam curved in the plane of the loads to a radius that is very large relative to the depth of section. Loads induce both bending and direct compressive stress. Reactions have horizontal components, though all loads are vertical. Deflections, in general, have horizontal as well as vertical components. At supports, the horizontal components of the reactions must be resisted. For the purpose, tie rods, abutments, or buttresses may be used. With a series of arches,...