254 APPLIED MECHANICS 
pitches, suitable joints, and provision for the attachment of the cross 
girders, ete. Some details may need revision. From this drawing the 
working drawings may be made. . 
To complete the bridge the following calculations are ne eit % 
Cross Girders and Rail Bearers.—These carry a definite portion of 
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ba dieh5fe —~ — =~ = -4"Pitch- --- ---- hd 62k ---4" Pitch= ~ 
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Holes for Bolts. 
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Meda tegte -—~-——-—- ~~ 4' Pitch —-- -------- - *5%5e ---4'Pitch--- 
Fie. 384. 
the bridge floor and a live load, consisting of one or more of the heaviest 
wheel loads. Design them as plate web girders (p. 216), doubling the 
live load to reduce it to an equivalent dead load. The working stress 
may be taken at 74 tons per square inch in tension. 
Floor Plating.—This may be considered as carrying a certain dead 
