632
MODERN GASWORKS PRACTICE
or R
co
r r
ü
8LD,
i.e. the overturning force due to the wind amounts to 8 LD.
Snow Pressure
Show pressure may be considered equal to 5 1b. per square foot on one-fourth of the area of the dorne, and acting at a point of one-sixth the diameter from the top curb.
Then if Ws = the total weight of snow, this acts at a distance of ? froip the
6
edge, or - from the centre of the bell.
To find total weight of snow :—
Total area of dome = -7854 D2.
•7854
. •. Portion covered by snow = -
. , x . -7854 D2 E
or, weight oi snow = —■' X ■>
II o CO u to
(0-981 is very nearly 1, and for the purposes of calculation Cripps considers that it may be assumed equal to 1.)
Therefore, total weight of snow = D2 1b.
Now the snow gives rise to a tilting moment.
WsX D =D2X~, 3 3’
or
wl
This moment is resisted by the reaction Rs at the top of the columns, and the moment of the reaction = Rs X L.
2] leo
I!
Co
PH
or
CO I QI
II
<x>
Ph
3L
in
Considering the results of wind and snow togeth.er, wc see that the total reaction the structure, that is the total force it has to resist, is—
8LD
Accordingly, the bending moment on the structure will amount to
"Öd' t-l u + S o L* i w
II
00 t-1
6
+
U
I w