84 THE KANSAS CITY BRIDGE.

The amount of material in the several trusses, including floor beams and
stringers, is as follows :—

 

 

LENGTH

or TIMBER. Wrovucut-Iron. Cast-I RON.
SPan.

130 35,739 ft. B. M. 44,053 lbs. 27,187 lbs.
176 57,854 se 72,969 “ 49,491 “
198 78,277 ee 89,449 *“ 54,119 <“
248 101,688 “ 147,482 “ 70,646 “

 

To this must be added 194,911 feet B. M. of pine lumber, 24,167 ft. of oak,
7,200 lbs. of wrought-iron, and 1,700 lbs. of cast-iron, used in the planking,
pavement blocks, hand rail, vertical bracing, anchor rods and chord covering,
on the fixed spans ; this additional amount includes the floor and footway of the
66 ft. span.

The method of manufacture by which the wrought-iron parts were pre-
pared rendered them free from the common danger of defective welds. The
chord links were made by upsetting the ends of flat bars of rolled iron till an
increase of section somewhat in excess of that required was obtained, and then
working down under the hammer and drilling the hole for the pin, leaving them
absolutely free from welds. The only weld in the panel ties was that formed
in joming the return end of the loop to the long bar; this weld would at most
be exposed to but half the strain upon the tie; and even if the weld were
absolutely worthless, the tie would have the full strength of a hook around the
chord-pin. For these reasons, it was not considered desirable to test every
piece of iron with a moderate strain of 20,000 to 25,000 Ibs. to the inch, as is
often done for similar works. Such a strain could at most be expected to
reveal the defects of manufacture, which the methods here adopted precluded
the possibility of; while the effect of such a strain, by giving a set to the iron,
and impairing its perfect elasticity, would be deleterious rather than other-
wise. Samples of the iron were, however, taken and tested to breaking in an

hydraulic tester under a slow and long-continued strain, with the following
results :-—