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These uplifts are to be adopted both for finding the uplift stresses in trusses and for proportioning the end-lifting machinery; provided, however, that for the latter purpose no assumed uplift be less than twenty thousand (20,000) pounds for single-track drawbridges or less than forty thousand (40,000) pounds for double-track drawbridges.
WIND LOADS.
The wind loads per lineal foot of span for both the loaded and the unloaded chords are to be the same as those specified for fixed spans, the length of span, however, being that of one arm of the draw.
When the span is open, all the wind load is to be carried to the drum through the lateral systems. When the draw is closed, the wind load is to be carried to both the ends and the centre supports, the lower lateral system and bottom chords being considered to act as a continuous girder over four supports. The reactions at the ends and the centre can be taken from the curve for balanced live loads.
INDIRECT WIND LOAD OR TRANSFERRED LOAD.
The wind load on the upper chords is to be assumed to travel through the upper lateral system to the inner hips, when the span is open; then down the inner inclined posts to the drum, thus producing a transferred load on the leeward inclined post and a released load on the windward one. As the upper lateral system is not continuous between the inner
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