=

weight of ice (g)

=

length of ice sample (cm)

density of ice 0.9 g/cm3

=

ri

p

=

3.14.

Alternatively, if the ice is melted and the volume of water is measured,

+

(2)

4 πρi L

2

where *V *= volume of melted ice (cm3)

rw = density of water 1.0 g/cm3.

Any consistent set of units can be used in the above calculations. In English units the densities of

ice and water are 56 and 62.4 lb/ft3, respectively.

As Eq. 1 and 2 indicate, the equivalent uniform ice thickness represents the ice load. Be-

cause uniformly thick ice forms the most

compact ice accretion, *t *will always be less

than the maximum thickness of the ice accre-

tion. The actual load, expressed as the weight

of ice per unit length, corresponding to a

specified uniform ice thickness, increases

with the size, or diameter, of the wire or angle

member or branch (Fig. 10). For example, 1-

in. uniform ice thicknesses on 0.5-in. wires,

1.5-in. conductors, and 3.5- 3.5- 1/2-in.

angles weigh 2, 3, and 7 lb/ft, respectively.

In the next section the calculation of ice

loads from hourly weather data using ice

accretion models is discussed. The derivation

of the formula used in the simple model

emphasizes the utility of describing ice loads

from freezing rain in terms of the equivalent

uniform ice thickness.

Because ice loads are difficult to measure,

they are often estimated by applying ice

accretion models to weather data. The weath-

er elements that are required for modeling the

accretion of ice in freezing rain are the

present weather code, which indicates wheth-

amount, and wind speed. Many models also

use air temperature and some use dew-point

9

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