General Order 64-A

Section IV

Strength Requirements For All Classes Of Lines

47.4    Change in Grade of Construction

Where sections of higher grade construction are located in lines of lower grade construction the longitudinal load on each end supports of such sections at the level involved shall be taken as an unbalanced pull in the direction of the higher grade section equal to the total pull of all conductors in that direction.  For spans not exceeding 500 feet in length, where the pull in the direction of the higher grade section exceeds 30,000lbs., the loading requirements may be modified to consider 30,000 lbs. plus one-fourth the excess above 30,000 lbs., to a maximum of 50,000 lbs.  The construction of the end supports (including poles, structures, towers, crossarms, pins, insulators and conductor fastenings) of such sections shall be such as to withstand at all times the load specified with a safety factor at least equal to unity.