Pole Overturning Moment and Bending Moment 45-Foot Wood Pole Embedded 6 Feet in Soil per Rule 49.1-C, Table 6 4, Douglas Fir Pole) Without With 7-Foot PoleTop PoleTop Row Forces and Moments Extension Extension Overturning Force 2 Feet Below Pole Top: 1,485 1,259 RUS 12.1 Equation 1 Pounds Pounds Soil Condition = Average. Soil Constant = 70 54,953 55,411 Overturning Moment at Ground Line 2 (Safety Factor = 1.0) Foot Pounds Foot Pounds 90,552 90,552 Bending Moment of New Wood Pole at 3 Ground Line (Safety Factor = 1.0) Foot Pounds Foot Pounds Before delving into the above table, we wish to acknowledge the fundamental safety issue raised by SED that a pole-top extension increases a pole’s overturning moment. We concur with the premise of SED’s proposed Rule 94.11 that a pole-top extension should not be allowed on a pole unless sufficient measures have been taken to ensure that the pole will not overturn. Rows 1 and 2 of the above table show that a 45-foot wood pole, without a pole-top extension, embedded 6 feet in average soil pursuant to Rule 49.1-C, Table 6, will overturn when a horizontal force of 1,485 pounds is applied 2 feet from the top of the pole (i.e., 37 feet above ground level), which equates to an overturning moment of 54,953 footpounds (fp.) at the pole’s ground line. Rows 1 and 2 of the above table further show that a 45-foot wood pole with a 7foot poletop extension, when embedded 6 feet in average soil, will overturn when a horizontal force of 1,259 pounds is applied 2 feet from the top of the combined
Pole Overturning Moment and Bending Moment 45-Foot Wood Pole Embedded 6 Feet in Soil per Rule 49.1-C, Table 6 4, Douglas Fir Pole) Row Forces and Moments Without PoleTop Extension With 7-Foot PoleTop Extension 1 Overturning Force 2 Feet Below Pole Top: RUS Equation 12.1 Soil Condition = Average. Soil Constant = 70 1,485 Pounds 1,259 Pounds 2 Overturning Moment at Ground Line (Safety Factor = 1.0) 54,953 Foot Pounds 55,411 Foot Pounds 3 Bending Moment of New Wood Pole at Ground Line (Safety Factor = 1.0) 90,552 Foot Pounds 90,552 Foot Pounds Before delving into the above table, we wish to acknowledge the fundamental safety issue raised by SED that a pole-top extension increases a pole’s overturning moment. We concur with the premise of SED’s proposed Rule 94.11 that a pole-top extension should not be allowed on a pole unless sufficient measures have been taken to ensure that the pole will not overturn. Rows 1 and 2 of the above table show that a 45-foot wood pole, without a pole-top extension, embedded 6 feet in average soil pursuant to Rule 49.1-C, Table 6, will overturn when a horizontal force of 1,485 pounds is applied 2 feet from the top of the pole (i.e., 37 feet above ground level), which equates to an overturning moment of 54,953 footpounds (fp.) at the pole’s ground line. Rows 1 and 2 of the above table further show that a 45-foot wood pole with a 7foot poletop extension, when embedded 6 feet in average soil, will overturn when a horizontal force of 1,259 pounds is applied 2 feet from the top of the combined
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