The Design of Multi-Span Arch Bridges on Elastic Piers

The subject of design of multi-span arch bridges has not received much attention in the text books. Space is not available for more than a few references. Hool derives equations for a two span fixed ended structure, and uses these for more than two spans by a process of successive approximations, though he claims that the method is not long. Spofford derives general equations for a fixed ended unsymmetrical structure of variable section with an indefinite number of spans, and gives an example of a three span design. His equations are general, and are similar in principle to those given in this paper, though they are of a very complicated appearance. Hayden gives equations and an example of the design of a two span portal frame with hinged ends. Parcell and Maney give an example of a four span fixed ended portal frame based on the slope deflection method. A very fully worked out method derived from the theorem of strain energy is given in a paper by Frankland. This is, however, not generally available in this country, and it is also, perhaps, rather too mathematical for most engineers. The methods of Hardy-Cross and Southwell will be familiar.

J.J. Leeming