Page 109 - McWane Poles Sales Manual 2024

Sales Manual • 2024
109
Pole Capacity
McWane poles are classified by pole tip load capacity in pounds or kips (1,000 pounds) applied two feet
down from the pole tip. The pole tip load capacities correlate with ANSI O5.1 wood pole class capacities
after the NESC Grade B Construction strength reduction factor for wood (.65). There is no NESC strength
reduction factor for metal poles.
Pole capacities are also given in pole bending moment capacity in pound-feet or kip-feet at the ground
line. Ground line bending moment is a function of the load applied on the pole and the distance of the
force from the ground. McWane’s stated bending moment capacities are calculated by multiplying the
stated tip load capacity by the distance from the ground to a point two feet below the pole tip. Assumed
embedment depths are based on ANSI O5.1. Pole owner will determine actual embedment depths.
Pole Class Example: Class C1 – 50’
Pole Length = 50 feet
Embedment Depth: 7
Tip Load Capacity: 2,925 pounds or 2.93 kips
Moment Arm = 50 feet – 2 feet – 7 feet = 41 feet
Bending Moment = Force [Tip Load] x Distance [Moment Arm]
Bending Moment = 2,925 pounds x 41 feet = 119,925 pound-feet
Bending Moment = 119,925 pound-feet x 1 kip / 1,000 pounds = 119.9 kip-feet
McWane poles have been designed with PLS Pole modeling software by a Professional Engineer. PLS
software utilizes formulas published by the AISC to determine the pole bending moment capacity along
the length entire of the pole. The formula for allowable bending moment at a pole cross section is as
follows:
Bending Moment Capacity Calculation Example: Class 1 – 50’ pole
Wall Thickness: .29 inches
Pole Diameter at Ground Line: 13.26 inches
Pole Radius at Ground Line: 6.63 inches
Yield Strength = 42,000 psi
Bending Moment Capacity = Yield strength [FY] x Section Modulus [S]
S = Moment of Inertia [I] / Radius [C]
I = (Pi/64) x (OD^4 – ID^4)
I = (3.1416/64) x ((13.26 inches)^4 – (12.68 inches)^4) = 248.66 inches^4
S = 248.66 inches^4 / 6.63 inches = 37.50 inches^3
Bending Moment Capacity = 37.50 inches^3 x 42,000 psi = 1,575,092 pound-inches
Bending Moment Capacity = 1,575,092 inch-pounds x 1 foot / 12 inches = 131,257 pound-feet
Bending Moment Capacity = 131,257 foot-pounds x 1 kip/1,000 pounds = 131.26 kip-feet
PLS also calculates the bending moment capacity at GL of a C1050 is 131.26 foot-kips.