Transactions of the American Society of Civil Engineers Volume 16 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1887 Excerpt: ... criticisms apply on account of the difficulty of including, in formula sufficiently simple to render their use general, many of the conditions which enter into the proper design of a bridge. Charles J. Morse, M. Am. Soc. C. E.--I have found Professor DuBois' paper very interesting, and think his formulas more closely approximate the analytical solution of the much vexed problem of the weights of bridges than any I have seen. I think his method of making separate calculations of floor and bracing preliminary to finding the weights of the trusses is the correct method of procedure for determining an accurate formula, although more tedious of application. The formula he obtains is, however, only an approximation and not a solution. It comes nearer a solution because it includes, or attempts to include, one more condition of the many involved, viz., the strut formula or varying unit strain. His formula for stringers is simple and accurate for the flanges and web. The "details," such as end connections, ribs and fillers, rivets, etc., are provided for by assuming the web to be one-half an inch thick for all depths and lengths. The same formula applies to floor beams by changing the uniform live load to suit their conditions of loading and to plate girders, deck or through, after first calculating the bracing and floor systems. Whether this web assumption accurately provides for the details, we have not had time to determine. The formula for the weight of truss is derived by summing the expressions for the weights of each principal part, but takes no account of details whatever until the strut formula is introduced. This strut formula is introduced by assuming a value for the square of the radins of gyration, in terms of the panel loads, number of pane...