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General Order 64-A


Section IV


Strength Requirements For All Classes Of Lines


43.1    Heavy Loading


Heavy loading will be considered as applying to all parts of the State of California where the elevation exceeds 3000 feet above sea level, except where United States weather reports, over a term of years, show that different conditions exist.  (See Appendix A for map indicating the approximate location of the territory subject to heavy loading.)  This loading shall be taken as the resultant stress due to wind, ice and dead weight under the following conditions:


A.    Wind

A horizontal wind pressure of 6 pounds per square foot of projected area on cylindrical surfaces, or 10 pounds per square foot on flat surfaces shall be assumed, except where wind velocities greater than those specified frequently occur; in which case a 25% increase of wind pressure shall be assumed.  Where latticed structures are used, the actual exposed area of one lateral face shall be increased by 50% to allow for pressure on the opposite face, provided this computation does not indicate a greater pressure than would occur on a solid structure of the same outside dimensions, under which conditions the latter shall be taken.


B.    Ice

A radial thickness of one–half inches of ice, weighing 57 pounds per cubic foot, on all conductors shall be assumed in computing vertical and wind loadings.


C.    Temperature

This shall be considered at the time of maximum loading to be 0° F.  The normal temperature for computing erection conditions is 60° F. Maximum temperature (in computing sag under this condition) shall be assumed as 130° F.