Elastic Equilibrium in the Theory of Structures

The standard specifications and formulas used in structural design, were devised to meet the problems encountered in ordinary bridge and building construction. They are well adapted to this purpose and have been found convenient and practical. When, however, an attempt is made to treat certain special problems, the limitations of these standard formulas become apparent. For instance, in the reinforcement of existing structures, an investigation of their strength depends on a rational analysis of their loads, stresses, and strains, and the design of their reinforcement must be based on such analysis, rather than on any empirical formulas. Another class of structure which demands special treatment is that used in railroad electrification work for the support of transmission wires, trolley catenary wiring, outdoor sub-station wiring, and switching. For some years, the writer has been actively engaged in the design of such structures, and has found it entirely practical to use bents which, while thoroughly braced, neither follow the usual design nor stay within the limits set up in some of the conventional rules.