— • lbO — 
For the lower lateral system we have the moving panel wind» load equal to 
=>.52 tons, and the static panel wind load = - = 2.10 tons. 
The secant will not differ essentially from that found for the upper lateral 
system. We can therefore fill out the following table of data, the notation cor- 
responding with that of Chapter IX. 
This completes the proportioning of the main members of the trusses. 
The sizes and weights of the track stringers and floor beams we will take 
directly from Tables XI. and XII. , for the method of proportioning these members 
was sufficiently exemplified in Chapter XII. 
We can either interpolate the sizes of the lateral, portal and intermediate atrutsj 
and of the lateral and vibration rods from Table XIII. or determine them more 
exactly by calculation. For the purpose of exemplification we will adopt the latter 
method. 
Let us begin with the upper lateral system. Tlie panel wind load is 
180 x 21 1 QA A 
—2000 = 1 - 89 tons ， 
ttiid the iucliuation of the rods to the struts is about equal to the arc whoso tangent 
is the panel leugtli divided by the clear roadway or 
tan -1 = tail -1 1.533 or (vide Table II.) 56*53 へ 
Tlie corresponding secant is about 1.83 making tlie length of the diagonal 
18.7 x 1.88 = 25 feet. 
The following is, therefore, table of data 
n = 
= ö 
W - 
= 1.89 
W 
n 
= 0.2363 
and — sec 6 - 
= 0.4324 
Using the formulte at the beginning of Chapter IX. or employing Table Y., we ciui 
calculate tlie stresses in the lateral struts and rods and record them as in the ac- 
companying diagram, # 
