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From Fig. 55bb, on p. 1246 of B.E., we find the weight of superstructure
metal to be 7,350 lbs. per lineal foot of span; hence the total weight of metal
will be,
5 X 330 X 7,350 = 12,127,000 lbs.
Example No. 4
What is the total weight of metal in a double-track, steam-railway,
center-bearing swing-span, 350' long between centres of end supports,
having riveted trusses, and carrying a Class 50 live load?
Solution
From Fig. 55bb, on p. 1246 of B.E., we find the weight of structural
steel per lineal foot of a 350' fixed span to be 6,450 lbs.; and in Fig. 55ee
on p. 1249 thereof is given 83 as the percentage to apply for a swing span
of that length and the type stated; hence the total weight of metal will be,
6,450 X 0.83 X 350 = 1,874,000 lbs.
Example No. 5
A 540', riveted, Petit-truss, highway span with paved roadway on reinforced concrete base and with reinforced-granitoid sidewalks, for which the
total live load per lineal foot of span for trusses is 3,200 lbs., has a dead
load, exclusive of weight of trusses, equal to 7,200 lbs. per lineal foot, the
total clear width of deck from out to out being 60'. What is the weight of
carbon steel in the two trusses required to carry this loading?
Solution
From Fig. 7e, on p. 131 of B.E., we find the coefficient for impact with
n= 60/20 = 3 to be 0.05; hence each truss load per lineal foot, exclusive of its
own weight, will be as follows:
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