THE STORAGE OF GAS
641
shear resolved in the direction of the struts—then, if we have four panels— 1 + 2 + 3 + 4 = 10,
4
. •. Tension in tie nearest abutment = — of S,
10
3
„ „ tie in 2nd panel — — „ „
” 1 10
2
„ „ tie m 3rd „ = — „ „
„ „ tie in. 4th „ = — ,, „
Similarly (see reciprocal diagram, Fig. 390),
4
Compression in strut nearest abutment = — of Ss
3
,, ,, „ in 2nd panel = ,, ,,
„ „ „ ' „ ~ i ,, ..
In the exarriple already considered the height of the columns was 80 feet, the distance apart 16 feet, and it may be assumed that there would be four equal panels as in Fig. 392.
The length of diagonals AC and BD is readily calculatecL Then—
24 L2 + D2
Maximum vertical shear =--------------- tons = 16-57 tons.
10,000
Resolving this in direction of struts, we get—
Total compression in struts = 16-57 X ~ = 13-24 tons.
Compression in bottom strut = — X 13-24 =5-29 tons.
Resolving 16-57 tons in direction of ties, we get—
25'6
Total tension in ties = 16-57 X ~ = 21-2 tons.
4
Tension in bottom ties — — X 21-2 — 8-5 tons.
The above calculations give the maximum compressive and tensile stresses occurring in struts and ties, the members in the lowest panel being subjected to this loading. From previous Statements it will be seen that the stresses in the individual struts and ties decrease towards the top of the framework ; hence, theoretically, the section of these members may be reduced in proportion. In practice, however, it
T T