Engineering Volume 10

Engineering Volume 10

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1870 edition. Excerpt: ...they indicate the maximum deflection of an elastic beam under a suddenly imposed load to be double that of the final deflection after oscillations have ceased. The reason for this is obvious enough, for the work done by the beam must be equal to that done by the load, and as the latter is equal to the product of the load into the ultimate deflection, the former must be equal to the product of the mean resistance of the beam into the same deflection; hence the mean resistance of the beam must be equal to the load, and as the resistance is nil at the commencement of the bending, it must be equal to double the load at the termination. But the conditions of the rolling load on a railway bridge are not analogous. The load is not sufliciently suddenly applied, and the horizontal motion and via viva of the train destroys other conditions. It might at first be concluded that at least the cross girders of a bridge spaced at intervals of a yard only, and where consequently at 60 miles per hour the load would be imposed in the thirtieth part of a. second, would constitute a case of suddenly imposed load and double strain, but experience does not bear out this conclusion. In an instance observed by the writer the deflection of some 8 in. cross girders, amounting to ths of an inch under the driving wheels of the engine when at rest, was increased to Q in. only when the engine traversed the bridge at considerable speed. In fact, in this case it was evident that the work done in deflecting the several girders was not performed, as in the case of a suddenly applied load, by averlical descent of the weight at each girder, but by increased horizontal traction on the whole train; in the same manner as the wheel of a road vehicle passing over more

Product details

  • Paperback | 922 pages
  • 189 x 246 x 46mm | 1,610g
  • United States
  • English
  • black & white illustrations
  • 1236875834
  • 9781236875839