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 MIL-HDBK-1001/5A
the same criteria as the primary drain system, by the
"contracted-weir" formula.
EQUATION: Q (ft 3/min.) = 200(b - 0.2H) H 1.5
(1)
where
b = scupper width (feet)
H = hydraulic head (feet), assumed 2-inch maximum depth
Have the total scupper cross-sectional area be a
minimum of 3 times the cross-sectional area of the primary
vertical drains, with minimum individual 3-inch scupper depth and
minimum width/depth ratio of 2.5.
2.2.2
Deflections. Deflections maintained within normal
limits (refer to par. 2.3.1) will have no practical effect on
drainage on a roof surface with the minimum roof slope.
2.2.3
Expansion Joints. Roof expansion joints are
recommended at the following locations:
a) Junctures between changes in deck material (e.g.,
from steel to concrete);
b) Junctures between changes in span direction of the
same deck material;
c)
Junctures between an existing building and later
addition;
d) Deck intersections with nonbearing walls or
wherever the deck can move relative to the abutting wall, curb or
other building component;
e)
Maximum spacings of 200 to 300 feet (61 to 91
meters);
f)
Junctures in an H, L, E, U, or T-shaped building;
g)
At building expansion joints.
Expansion joints should be located at high points, with
drainage directed away from them. They should allow for relative
movement in three directions, vertical, transverse, and
longitudinal, detailed for minimum 8-inch (203-millimeter),
5
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