220 CMR, § 125.24

Current through Register 1536, December 6, 2024

Section 125.24 - Loadings

(1)Loading on Conductors. The loading on conductors at 0° F shall be assumed to be:

W_e = W_v² + W_h² + K

where:

W_e = Resultant loading in pounds per foot of conductor length.

W _v = Vertical load in pounds per foot of conductor length, covered with 1/2 inch radial thickness of ice.

W_h = Transverse loading in pounds per foot of conductor length due to a transverse, horizontal wind pressure of four pounds per square foot upon the projected area of the conductor, covered with 1/2 inch radial thickness of ice.

K = 0.29 for bare conductor of copper, steel, copper alloy, copper-covered steel, aluminum-covered steel, and combinations thereof

K = 0.31 for bare conductors of aluminum (with or without steel reinforcement).

In applying loadings to bare stranded conductors, the coating office shall be considered as a hollow cylinder touching the outer strands.

Ice is assumed to weigh 57 pounds per cubic foot. The weight of ice in pounds per lineal foot can be calculated by the formula:

Weight of Ice = 1.243 t (D+t) where:

D = Diameter of conductor in inches

t = Radial thickness of ice in inches

(2)Loadings on Line Supports.

(a)General. The loads upon line supports shall be the loads delivered by the conductors, including conductor tensions, when loaded as specified in 220 CMR 125.24(1), assuming all conductors intact, plus the weight of the supports plus the wind load on supports. In combining loads, due account shall be taken of different directions of loads.

(b)Weight of and Wind on Conductors. The vertical load delivered to the support by the conductor shall be calculated using the weight span S _v, which is the horizontal distance between the low points of sag in the two spans adjacent to the support concerned, i.e., W_v x S_v .

The wind load delivered to the support by the conductor shall be calculated using the wind span S _h , which is the average of the two spans adjacent to the support concerned, i.e., W_h x S_h .

(c)Weight of Ice on Supports. The weight of ice upon supports may be ignored for the sake of simplicity.

(d)Wind Loading on Supports. The minimum wind loading shall be assumed as four pounds per square foot on projected area of cylindrical surfaces, and 6.4 pounds per square foot on flat surfaces.

For latticed bodies of structures, the actual exposed area of one face shall be increased by 50% to allow for the pressure on the opposite face. This total, however, need not exceed the pressure which would occur on a solid structure of the same outside dimensions. The results obtained by more exact calculations may be substituted for the values obtained in 220 CMR 125.24.

(e)Wind Direction. Wind direction shall be assumed which will give the maximum stresses in all parts of the structure, proper reduction being made to account for the reduced wind pressure on the wires resulting from the angularity of the application of the wind to the wires.

(f)Simultaneous Application of Loads. All applicable loads shall be taken as acting simultaneously.

220 CMR, § 125.24