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THE design of a bridge or any other engineering project implies the adjustment of certain means to certain ends, and both means and ends are considered in terms of money. Co-existing with the financial problems involved is economic design. Further, a
bridge project implies not only the expenditure of money for the attainment of certain ends, but the meeting of all costs as they arise. The expenditure of a capital sum of money in first cost, and the meeting of capital charges and revenue costs out of income, is undoubtedly a financial problem, and the methods by which financial equilibrium is to be obtained must be established before the design is completed. Economic design implies financial equilibrium. In analysing a bridge project a wide interpretation must be given to the term "Finance" met in Economic Science.
W. Nelson Elgood
Sir,-I shall be glad if you will kindly find space for a reply to Mr. R. A. Skelton’s remarks in the June issue of the Journal, regarding my letter in the April number.
The beam is probably the most useful constructional unit which the modern engineer has at his disposal. It is, therefore, very necessary that he should be fully acquainted with all its properties and with its behaviour under all kinds of loading. Thanks to early investigators and mathematicians, it is possible to calculate the bending and shear stresses in beams of symmetrical section with a fair amount, of accuracy. Under cerfain conditions, however, it becomes necessary to consider the elastic ability of a
beam or of its various parts. Sometimes it is found that the web is too thin and will fail by buckling, or that the flanges have not sufficient resistance against wrinkling and, where there is not sufficient lateral support, a long beam may collapse wholesale by lateral buckling. It thus appears that a study of the elastic or secondary causes of failure is necessary before a complete mastery of the subject can be obtained. This paper deals merely with the lateral stability of beams, but it is not intended to give a complete account of all problems arising out of this subject. An attempt, has
been made to put forward some known facts and theories most of which are the result of
other peoples' researches: and to apply the results as far as possible to practica1 working conditions.