BUCKLED-PLATE FLOORS.

If the Engineer so desire, a buckled-plate floor with ties in ballast may be used instead of the wooden floor, in which case the size of the ties may be reduced to 6" X 8" X 8'.

All buckled-plate floors mast be thoroughly drained so as not to retain water, and the upper surface of the buckled plate must be protected from rusting by a liberal use of the best obtainable preservative coating.

SUPERELEVATION ON CURVES.

On curves the outer rail will be elevated the proper amount for the degree of curvature and for the assumed medium velocity of trains; and this elevation must be framed into ties, as no shims will be allowable anywhere under ties or rails, excepting in the case of very sharp curves requiring a superelevation exceeding three (3) inches in five (5) feet, on which long shimming timbers are to be bolted to the top flanges of the outer longitudinal girders, or short, substantial ones to tops of ties, so as to give the required superelevation.

The formula to be used for total superelevation on standard-gauge roads is:

where E is the total superelevation in feet of the exterior rail above the interior rail, V is the assumed velocity of train in miles per hour, and R is the radius of the curve in feet. The total superelevation is to be obtained by depressing the inner rail and elevating the outer one equal amounts, thus preserving the grade of the centre line.

SPACING OF STRINGERS, GIRDERS, AND TRACKS.

In general, stringers for through bridges shall be spaced eight (8) feet centres or less for single-track bridges and six (6) feet six (6) inches for double-track bridges; and half-through plate-girder bridges. In elevated railroads the spacing of the longitudinal girders may be made as small as five (5) feet centres.