Method for making composite utility pole

A method of making a hollow utility pole having a butt portion, a medial portion and a tip portion, said method comprising the steps of:

• determining the length of the pole to be fabricated;
• selecting a mandrel having a representative diameter and length on which to make the pole;
• establishing test stations spaced incrementally from the tip portion to the butt portion;
• applying resin-coated, fiber reinforcing strands over the mandrel;
• determining, at each of said test stations, if the thickness-to-diameter ratio for the wall thickness of the resin-coated, fiber reinforcing strands laid on said mandrel is equal to or less than 0.015;
• applying additional circuits of resin-coated, reinforcing strands as are necessary to satisfy the thickness-to-diameter ratio at the first test station;
• calculating the stress resistance at each of said test stations by virtue of the formula:
• ##EQU14## determining if the acceptable stress resistance under a predetermined load calculated at said same test station is greater than the stress resistance required for said test station;
• applying additional circuits of resin-coated, reinforcing strands as are necessary to satisfy the required stress resistance at said test station before proceeding;
• calculating the critical load at each of said test stations by virtue of the formula:
• ##EQU15## determining if the actual loading to be applied to the pole is lower than the critical load at which the pole would buckle at said station;
• adjusting the acceptable stress if the preselected, rated load is not less than the projected failure load and the rated load does not exceed the projected failure load by a predetermined margin of safety;
• applying additional circuits of resin-coated, reinforcing strands as are necessary to assure that the calculated and adjusted maximum stresses satisfy the margin of safety criterion;
• continuing the testing and applying steps at each test station until the pole is satisfactorily laid up on the mandrel;
• and,
• curing the resin to complete the pole.

A method of computer-modelling a hollow utility pole for subsequent manufacture from a composite FRP, the utility pole having a butt portion, a medial portion and a tip portion, said :method comprising the steps of:

• determining the length of the pole to be fabricated;
• selecting a mandrel having a representative diametral configuration and a length to accommodate the full length of the pole from the butt portion to the tip portion;
• establishing test stations spaced incrementally along the mandrel from the location where the tip portion will be formed to the location where the butt portion will be formed;
• simulating the application of resin-coated, fiber reinforcing strands in a circuit from the location of the butt portion to the location of the tip portion;
• determining, at a test station closest to the tip portion of the pole, if the thickness-to-diameter ratio for the wall thickness of the circuit of resin-coated, fiber reinforcing strands is equal to or less than an established constant;
• simulating the application of additional circuits of resin-coated, reinforcing strands as are necessary to satisfy the thickness-to-diameter ratio at the first test station;
• and,
• determining if the thickness-to-diameter ratio on the next successive test station is equal to or greater than the established constant;
• simulating the application of additional circuits of resin-coated, reinforcing strands as are necessary to satisfy the thickness-to-diameter ratio at the next successive test station;
• continuing the testing steps and the simulation of additional circuits, as needed, at each test station until the thickness-to-diameter test has been satisfied along the selected length from the tip portion toward the butt portion;
• determining if the acceptable stress resistance under a predetermined load calculated at the successive test stations is greater than the stress resistance required for each respective test station;
• simulating the application of additional circuits of resin-coated, reinforcing strands as are necessary to satisfy the required stress resistance at each station before proceeding;
• calculating the stress resistance at each station by virtue of the formula:
• ##EQU16## where:
• M=the moment produced by a selected load;
• c=the distance from the neutral axis of the pole to the outer surface thereof;
• and,
• I=the moment of inertia for the cross section of the pole at the test station;
• evaluating the tip deflection at each station when the simulated pole is subjected to the rated load;
• projecting the failure load from the tip deflection at each station by virtue of the formula:
• ##EQU17## where F.sub.R =the rated load causing the beam to deflect;
• F.sub.P =the projected failure load;
• a=the distance from the plane of fixation to the point where the rated load F.sub.R is applied to the beam;
• L.sub.A =the distance from the plane of fixation to the end of the beam;
• C=the proportionality constant;
• and,
• .delta.=the deflection of the beam under the applied load;
• determining the proportionality constant using a linear regression analysis of the failure load versus the load deflection parameter;
• substituting a negative eight hundred, forty-three ten thousandths (-0.0843) for the proportionality constant if glass reinforcing fibers having a yield of two hundred and fifty (250) yards per pound of glass are employed;
• adjusting the maximum stress when the rated load is greater than the projected failure load;
• determining if the calculated stress resistance is less than the adjusted maximum stress;
• and,
• simulating the application of additional circuits of resin-coated, reinforcing strands as are necessary to assure that the calculated stress is less than the adjusting maximum stress.