Referring to the Table for bolts, we find that 2-1/8 gives a strength
a little in excess, and will be the proper size. The next set of rods
bear the weight of the whole load, less that due to the two end
panels, and so on. Fig. 2, Pl. III, shows the manner of applying the
rods. The bevel block should be so fitted to the chord that it will
not have a crushing action.
=Counters.= Top and bottom chords are always used in this bridge, and
consequently the counter rods have only to sustain the movable load on
one panel. The weight of the moving load cannot be more than 2000 lbs.
per lineal foot which, for a panel of 10 ft., gives 20000 lbs., or
10,000 lbs. for each set, and if we have two rods in a set, the strain
on each rod will be 5000 lbs., increasing this for inclination, we
shall have,