MIL-HDBK-1025/5
Environmental Factors and Protection
2.7
Snow
2.7.1
Factors
2.7.1.1
In colder regions, floating-pier systems are seriously
a)
affected by excessive snow loads. Only the covered floating berths are apt to
be submerged by a heavy snowfall.
Most roofs of floating sheds cannot be made steep enough to
b)
ensure that the snow will slide off. Roof area multiplied by 6 times the
anticipated maximum snow depth in feet will give the extra weight in pounds
that is carried by flotation. If this exceeds the design live load, the
amount of flotation should be increased sufficiently to support the difference
without submergence of the flotation units.
Protection.
Measures may include the following:
2.7.1.2
Boats berthed in the open during the snow season in cold
a)
regions shall be covered with tarpaulins, fitted canvas or reinforced plastic
covers.
To protect against the submergence of floating systems, boats
b)
are removed from the water to dry storage before the winter season sets in. A
common practice is to store the larger craft on cradles on land and cover them
during the winter season. Smaller boats are generally stored with the keel up
for better shedding of snow and rain.
Ice
2.7.2
Protection.
Methods for reducing ice damage include:
2.7.2.1
In regions where temperature drops are not excessive and
a)
natural freezing does not cause a thick ice sheet, ice formation can be
prevented near piles and floating slips by forced convection currents. This
system is based on the principle that water reaches its maximum density at
about 39 F ( 4C) and tends to stratify in layers with the heaviest on the
bottom. Forced convection of this warmer but denser water from the bottom to
the surface when the surface temperature approaches 32 F (0 C) will prevent
or at least postpone freezing.
If a bubbler system is not used, sheet ice damage can be
b)
reduced or prevented by proper design provisions. Piles are driven deep
enough in some materials to develop sufficient withdrawal resistance against
lifting by ice. Flotation components of floating systems are designed with
rounded or tapered bottoms.
On rivers, estuaries and lakes, the following measures are
c)
expedient:
often
1) Pile clusters, often with sloping tops, are placed in the
path
of ice floes to break them up and divert them from the harbor basin.
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