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<br />UNIVERSAL MANUFACTURING CORPORATION
<br />T ,� 12357 East 13 Mile F1d. Warreii. MiLhlyan 4©Oe9 13131 774-4140
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<br />The Standard PS-222-A is ultra -conservative in its specifica-
<br />tion of wind loadings of 30, 40, and 50 pounds per square foot.
<br />This conservative approach results not from its choice of design wind
<br />velocities but from its specification of "A nominal value of K (for
<br />pressures on the projected areas of flat su faces) is .004." Hence
<br />the wind pressure is P = K V2 or P = 0.004V�. The coefficient in
<br />that equation depends directly upon air density. In our pest calcu-
<br />lations we have used the value of 0.00256 which is based upon so
<br />called "standard conditions" (150 Centigrade (590 F), 760 mm Hg).
<br />Perhaps this is less conservative then is desirable. If we assume a
<br />temperature of -400 F, the density of the air then yields a coeffi-
<br />cient of 0.0031. If we use this coefficient and the wind velocities
<br />(87, 100, 110 mph) inferred in the Standard we arrive at pressures
<br />of 23.4, 31.0, and 37.5 pounds per square foot for the loading zones
<br />A, A, and C respectively. It is my opinion that it is entirely
<br />reasonable and prudent to offer towers based on these wind pressures
<br />even though they do not comply with the Standard RS-222-,A.
<br />Accordingly, given belcw
<br />are effective antenna areas based on
<br />wind pressures of 23.4, 31.0,
<br />and 37.5
<br />pounds per
<br />quare foot and a
<br />factor of safety of 1.67 based
<br />on a minimum yield
<br />of 35,000 pounds
<br />per square inch:
<br />30 Foot Tower
<br />A
<br />B
<br />C
<br />11,11,14
<br />2.75
<br />1.25
<br />0.50
<br />11,14,18
<br />6.75
<br />4.50
<br />3.25
<br />14,18,18
<br />8.25
<br />5.25
<br />3.75
<br />14,18,22
<br />15.50
<br />11.25
<br />8.75
<br />140 Foot Tower
<br />11,14,14,18
<br />2.50
<br />1.25
<br />0.50
<br />14,14,18,18
<br />4.25
<br />2.00
<br />1.00
<br />11,14,18,22
<br />6.75
<br />4.50
<br />3.25
<br />14,18,18,22
<br />8.25
<br />5.25
<br />3.75
<br />14,18,22,22
<br />10.5
<br />6.50
<br />4.50
<br />14918,22,26
<br />15.50
<br />11.25
<br />8.75
<br />50 Foot Tower
<br />11,11,14,18,22
<br />2.75
<br />1.25
<br />0.50
<br />11,14,18,18,22
<br />4.25
<br />2.25
<br />1.0
<br />11,14,18,22,26
<br />6.75
<br />4.50
<br />3.25
<br />V.,18,'2.,22,26
<br />10.50
<br />6.50
<br />4.25
<br />14,10,22,26,26
<br />11.0
<br />6.50
<br />4.0
<br />-5-
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