Magnetic straking such as for utility or communications tower

Magnetic straking can optionally be temporarily attached to a ferromagnetic structure or other structure capable of magnetic attachment thereto, allowing observation or testing of the structure's performance before optional permanent attaching of such straking to the structure, such as by welding or the like.

TECHNICAL FIELD

This document pertains generally, but not by way of limitation, to structures exposed to fluid flow, and more particularly, but not by way of limitation to magnetic straking such as for a utility or communications tower.

BACKGROUND

In a utility or communications structure or other structure that is exposed to fluid flow, such as wind flow, vibration can be induced in the structure due to the wind or other fluid flow to which it is exposed.

SUMMARY

The present inventors have recognized, among other things, that such wind or other flow-induced vibration can impact the integrity of the structure, leading to cracking, premature wear, or even structural failure. For example, vortex shedding is a phenomena in which oscillating flow can take place when air moves past a structure at certain velocities, which can depend upon the size and shape of the structure. Alternating pressure vortices can be created downwind from the structure, and can detach periodically from either side of the structure. The structure can tend to move toward the low-pressure zone. If the vortex shedding matches the resonance frequency of the structure, the structure can begin to resonate. Harmonic vibrations can occur, which can create the potential for structural damage or failure.

A fin or other straking can be used to interfere with wind flow past a structure, such as in a manner to inhibit or dampen vortex shedding. For example, a vertical cylindrical structure may have a protruding spiral fin about the structure such as to reduce or inhibit vortex shedding, thereby reducing or avoiding resonance or other structural wear upon the structure. Finite element analysis (FEA), such as can be performed using a computer simulation, can be used to determine the exact size, shape, and arrangement of a fin or other straking. The process of performing FEA simulation to determine a straking configuration, and then implementing such straking on a structure, can be time-consuming, tedious, and expensive. In practice, it is sometimes easier to iteratively weld straking elements piecemeal onto a metal structure such as a utility or communications pole or tower, and then test the amount of vibration reduction that is obtained for the welded arrangement of straking elements. If insufficient damping is obtained, more straking elements can be welded onto the structure. This can avoid the tedious process of FEA simulation and analysis. However, welding permanently attaches the straking element to the pole. This can lead to inefficient usage of straking materials if too many straking elements are welded to the pole. Moreover, if the straking arrangement is unsuitable, for example increasing flow-induced vibration, or insufficiently or incorrectly damping such vibration, it can be difficult to remove such welded-on straking elements.

Accordingly, the present inventors have recognized that magnetic straking elements can help by allowing temporary magnetic affixation to a ferromagnetic metal structure, such as is often used in a utility or communications pole or structure. This allows a user to magnetically mount one or more magnetic straking elements at desired locations upon the utility or communications pole or other structure, observe or test the effect of such straking elements on the structure, such as when the structure is exposed to wind flow, and then either move (or add or remove) one or more selected straking elements, until the user is satisfied with the performance of the one or more straking elements. Then, such straking elements can optionally be welded or otherwise permanently attached to the structure. This can avoid the tedious process of FEA simulation and analysis, and allow easy and convenient trial-and-error configuration and optional reconfiguration. At the very least, observation or verification of performance of the straking elements can be accomplished before permanent affixation of the one or more straking elements to the structure is performed.

DETAILED DESCRIPTION

This document describes magnetic straking that can optionally be temporarily attached to a ferromagnetic structure, allowing observation or testing of the structure's performance before optional permanent attaching of such straking to the structure, such as by welding or the like.

FIGS. 1A, 1B, and 1Cshow illustrative non-limiting examples of utility or communications structures, such as to which wireless communications equipment or wired communications or power lines can be attached.FIG. 1Ashows an illustrative example of a self-supporting tower.FIG. 1Bshows an illustrative example of a guyed tower.FIG. 1Cshows an illustrative example of a monopole, such as can be generally cylindrical, but with faceted flat sides forming a polygonal cross-section to provide the generally cylindrical structure. All or a portion of any of the structures shown inFIGS. 1A, 1B, 1C, can include a material that is ferromagnetic or otherwise capable of receiving a permanent magnet for magnetic attachment thereto.

FIG. 2shows an illustrative example of an elongate magnetic straking element200. In this example, the straking200can include an elongate section of angle iron201(or other angle material). In an example, the angle iron201can be vertically-oriented with respect to a vertically-oriented monopole or other structure extending upward from a base located on the ground, a rooftop, or elsewhere. For example, the straking200can be magnetically vertically attached on a flat faceted side of the vertical monopole shown inFIG. 1C. Such magnetic attachment can be provided using one or more permanent magnets202. The one or more permanent magnets202can be bolted (such as shown) or otherwise attached to a face205B of the angle iron201at one or more desired locations. For example, the magnets202can be affixed such as at or near one or more ends of the angle iron201, at one or more intervening locations along its length, or both. The angle iron201can include end offsets203, such as can extend orthogonally from the face205B of the angle iron201that extends parallel to the facet of the monopole or other structure to which it can be attached. The end offsets203such as can be used for welding (or other mechanical, chemical, or other permanent affixation technique) the angle iron201onto the faceted side of the monopole or other structure, such as after determining that the magnetically attached locations of the magnetic straking element200are indeed the desired locations for more permanent attachment. A height of the end offsets203can match a height of the permanent magnets202, such that the end offsets203can be conveniently welded to the underlying structure while the straking200is magnetically attached thereto using the permanent magnets202. Other offsets203can be provided elsewhere along the length of the straking200for allowing further welding, if desired. The magnetic straking element200can provide a fin204that juts out in a non-parallel (e.g., orthogonal) direction from the faceted side of the monopole or other structure. The fin204can disrupt wind flow around the structure, such as to provide fine tuning of wind flow around the structure, such as to inhibit, reduce, or avoid vortex shedding. The height of the permanent magnets202and the end offsets203can be selected to obtain a desired spacing from the underlying structure, which can help adjust the wind flow around the structure. Similarly, a height of the fin204can be selected to provide a desired degree of disruption of wind flow, such as to inhibit or prevent or accommodate vortex shedding.

This fin204can be provided by the face205A of the angle iron201that can extend orthogonally to a faceted side of the monopole or other structure. The straking element200can optionally also help provide structural reinforcement to the structure to which it is affixed, for example, in addition to serving the purpose of tuning wind flow around the structure, particularly after the straking element200is permanently affixed to the structure, after its performance has been observed, measured, or verified while being magnetically attached to the structure before being permanently attached thereto.

The fin204need not be orthogonal, but can jut outward at a non-right angle, if desired. The magnetic straking element200need not include an angle iron201, but can include another structure that can jut out from the monopole or other structure. For example, an elongate triangle iron element can be used as the magnetic straking element instead of an angle iron element, if desired. The triangle iron element can have a triangular cross section at any orthogonal cutline along its length. The terms “angle iron” and “triangle iron” are intended to refer to common terminology for such materials—however, they need not be made of an iron material, and need not be ferromagnetic. For example, a carbon fiber or a plastic or other polymeric magnetic straking element can be used, with permanent magnets attached thereto. When a magnetic material is used for all or part of the elongated member of the magnetic straking200, the permanent magnets202can optionally be integrated into the elongate magnetic material of the elongate magnetic straking element200. The magnetic straking element200need not be attached in longitudinal alignment with the monopole or other structure, but, if desired, can be attached at a desired angle thereto, such as to form a spiral-like or other configuration of multiple magnetic straking elements200. The elongate magnetic straking elements200need not be linear, but can be curved, if desired.

As explained herein, providing magnets202to allow optional temporary attachment to an underlying utility or communications tower or pole structure that is capable of magnetic attachment can allow reconfiguration of the magnetic straking elements200such as during an observation or evaluation period.

Although particular examples have been described with a utility or communications monopole as the underlying structure, any other structure capable of magnetic attachment thereto using permanent magnets202can use the present approach.

Also, although particular examples have been described with respect to addressing vortex shedding due to wind flow, structures subject to similar effects from other fluid flow (e.g., underwater structures subject to water flow) can similarly advantageously use the present approach, such as to allow observation or reconsideration before more permanent attachment.

VARIOUS NOTES