Pole Information Center

Wind-Load Calculations

For any questions about wind-load or foundation calculation services, please contact our sales team.

Wind-Induced Vibrations

Early in the pole selection process, considerations for aesthetic requirements (color, height, and shape), environmental factors (wind zones, location, and field conditions), and load restrictions (fixture, brackets, and total EPA) are made. At this point, it is important to adhere to the guidelines set forth by the American Association of State Highway and Transportation Officials (AASHTO). AASHTO has provided the 1994 Fastest Mile Wind Map and the 2001 3-Second Gust Wind Map. The standards and codes have been created from historical analysis and research.

These wind maps take the following into considertion:

• First- and second-moment effects
• Axial and torsional stresses
• Direct wind pressures on the pole and luminaire
• Bending
• Shear

First Mode Vibration

Adhering to the AASHTO wind maps, guidelines and standards as well as any local building codes should accurately allow for consideration of First-Mode Vibration during the pole selection process. First Mode Vibration is caused by sudden high-velocity gusts of wind, in which the maximum deflection occurs at the top of the pole. This can be viewed by the swaying of the pole - see Fig.1. The effects of First Mode Vibration are usually not harmful to the pole of the luminaire. These types of winds are mapped by AASHTO.

Aeolian Vibration

The phenomenon know as Aeolian (or Second Mode) Vibration is caused by low-velocity, steady winds, normally ranging from 5-35mph and giving rise to frequencies of 2-20hz. This vibration is believed to be predominantly caused by air vortexing around the structure. As this steady stream of air passes across the pole, vortices are formed on the backside of the structure. The vortices alternate from the top and bottom surfaces and create alternating pressures that tend to produce movement at right angles to the direction of the air flow. This vortexing causes a high-frequency, short-cycle harmonic reaction in the structure — creating extreme stresses. This phenomenon is site specific and is, unfortunately, not predictable. Aeolian Vibration can be altered by as little as the shape of the structure, changing the fixture style or location, or having an object such as a tree or building alter the wind pattern.

Vibration Control

Our vibration dampener is used to minimize the effects of wind-induced Aeolian Vibration. When this type of vibration is identified (it is site specific and unforeseeable), a dampening system is used to mitigate the stress effects.

The vibration dampening system consists of a length of chain encased in a plastic tube that runs approximately two-thirds the length of the pole. This piece disturbs the harmonic cycling of the shaft (Aeolian vibrations) by touching the inside surface of the pole in a random and spiral manner. The wind-induced agitation of the pole is then transferred to the tube and chain. The natural vibration frequency of the chain is out of phase with the natural frequencies of the pole. This condition — coupled with the energy-absorbing characteristics of the dampener — usually provides effective mitigation of the vibration effects.

Installation Procedures

Step 1

Insert square cut (lead end ) of the plastic tube through the hand hole and snake up the pole. The lower end is positioned and held captive on the edge of the hand hole by the notch in the tube. Do not kink the plastic tube.

Step 2

When the dampener assembly is pushed through the hand hole, it will slip down inside the pole to contact the pole foundation. It is essential that the dampener does not crush or damage the electrical wiring in the pole This can be readily accomplished by ensuring the lower end of the assembly slides down the pole, tight to one side.

Step 3

Electrical inspection is again required to check the system and verify safe operation.

Pole Installation

The following information is intended as a guide for the installing contractor. This information cannotbe comprehensive enough to cover all situations or the details of all structures. Therefore it is essential that the owner and contractor carefully plan all aspects of the installation process, not relying only on these guidelines to determine the steps to be followed. This is general information about standard American LitePole products. Special features required by individual owners my require unique installation methods. For these the contractor must be be familiar with the wener's plans and specitications and the American LitePole subemittal drawings (if any). Due to the varied methds used by contractors in actual field operations, Amerinca LitePole cannot be liable for structural damage occurring during erection.

Small Parts

The poles will be delivered along with the anchor bolts and template (if not pre-shipped) and a box of hardware. The box of hardware must be inspected at the time of delivery.

• 2-piece base cover with 4 push pins
• Pole cap (drill mount only)
• Can of touch up paint (standard colors only)
• Hand hole cover with gasket and back bar
• Grounding bolt and snap plug

Assembly in the Field

During production, our poles must be hung in order to travel through the powder-coat booth. To accommodate this, we drill two holes in the pole, one at the top and one at the bottom (opposite the hand hole). The hole at the top is plugged while the hold at the bottom of the pole is utilized as the grounding lug.

Shipping & Handling

Delivery

Shipping and handling light poles requires an experienced touch given the awkward size of our products. General Structures, Inc. will—at its discretion—choose the carrier it feels will provide the best service and delivery.

Most orders are shipped using (NEED NAME OF SHIPPER) — which specializes in shipping steel and aluminum light poles — or brokered with independent flatbed carriers to ensure our poles arrive damage free. Small parts orders or anchor bolts requested ahead of poles are shipped via UPS.

Every effort will be made to accommodate a customer request for a specific carrier if the customer accepts to pay associated freight costs. In these cases, the freight carrier and account number should be noted on the purchase order. Typically, poles will be delivered on a flatbed truck.

Reconsignment of a shipment may result in additional charges that will be the responsibility of the customer.

• It is the contractor’s responsibility to offload the poles, using a forklift or crane.
• Never lift a pole by inserting a fork through the end of the pole shaft.
• Unloading delays may result in additional charges to be billed to the customer.
• Hardware is typically sent with the poles, in a separate box.

Inspection

• Upon delivery, it is imperative the pole wrapping is removed.
• The contractor must thoroughly inspect the poles and ensure all items were delivered without any damage during transit.
• Any shortages or damages must be noted on the delivery receipt.
• Be certain to open, inspect, and count all hardware.

Storage

• Remove all onyx wrap and cardboard.
• If possible, store poles inside, away from the elements.
• Poles must be kept off the ground and not submerged in snow or water.
• Separate layers of poles with padded dunnage (dry, untreated wood).
• Generally, it is best to alternate poles top to bottom and bottom to top.
• Make sure that the dunnage is directly in line to one another to apply equal pressure on the poles.

Non-Compliance

• Wrapping left on pole may result in damage to the appearance of the finish.
• Cardboard may allow water to be trapped and condensation to build — causing staining.
• Wet dunnage and dunnage with a chemical makeup may result in damage to the finish.
• Unequal dunnage distribution may result in bending and/or warping of the pole.

Maintenance & Inspection

Regular inspection and maintenance of light poles and luminaires is extremely important. Quarterly to biannual inspections are recommended to maintain safety, longevity, and aesthetics. While there are many aesthetic features to be discovered during these inspections, the list below focuses on items where safety is a concern.

Pole and luminaire inspections should consist of — but not be limited to — the following:

Pole Shaft

Visually inspect pole shaft for areas of rust, corrosion, and any dents or signs that the structural integrity has been compromised.

Brackets and Arms

Visually inspect brackets, arms, luminaires, and welds to ensure there is no metal fatigue.

Handhole, Base, and Nut Covers

Ensure covers are securely attached

Anchor Bolts

Ensure all anchor bolt nuts are in place and securely tightened.

Grounding & Protection Against Electric Shock

The purchaser and installer must provide electrical groundings and warnings about electrical hazards in accordance with applicable codes.

Vibration

Inspect for signs of vibration, which include:

• Noise or humming in the pole
• Visual movement of the luminaire and/or pole
• Loosening of attachments
• Rust just above the weld at the base of the pole