THE KANSAS CITY BRIDGE. iil

Proceeding from the centre towards either end, these moments corresponding
to a full load decrease in intensity till they become positive, being every-
where determined by the ordinates of a parabola.*

The central chord strains will be :—

20,536,880 — 34.3 = 598,743 pounds.

The greatest positive moments (compression above and tension below)
occur when one arm only is loaded ; the greatest negative moments over the
pivot pier occur when both arms are fully loaded, and those at the centre of
each arm and near the ends of the draw take place when neither arm is loaded.+
The maximum moments at the end of each panel are given in the tables in
Appendix G, the values being obtained by measuring on a diagram the ordi-
nates of the curves of strain; the corresponding chord strains are likewise
given in the tables, their values being found by dividing the moments by the
depth of truss at the corresponding point. To find the strains which actually
take place in the chords, a correction must be made for the strain which is
carried horizontally by the members of the web; these corrected strains are
also given in the tables, the tensile strains being distinguished by a negative
sign ; as the strains carried horizontally by the web are all in tension, being
carried by the diagonal ties, the actual amount of compression in the chord
materially predominates over the tension.

The web is formed in two systems which are connected only through the
chords. As each system is supposed to carry but half the load, in calculating
the strains on their members the dead load will be assumed to be 480 pounds
to the foot, and the live load 560 pounds. The strain in each post will be the
same as the weight carried by the tie which depends from it ;§ the strain in each
tie is equal to the weight carried, multiplied by the proper coefficient for the
inclination of the tie.

*Shown on the eee in a broken line —, ——.—. —,—. —

+ The resultant curve of maximum intensity of ee for all parts of the draw, without regard to the
sign of the moments, is drawn on the diagram in a plain heavy line.

} Strictly speaking, plus the weight of the upper chord for one panel; this weight however is small, and
the calculation need not be complicated by it.

§ These corrected chord strains, expressed in tons of 2,000 pounds, are given on the skeleton diagram
on Plate XII.