CA1300846C - Breakaway utility pole inverted base structure - Google Patents
Breakaway utility pole inverted base structureInfo
- Publication number
- CA1300846C CA1300846C CA000570074A CA570074A CA1300846C CA 1300846 C CA1300846 C CA 1300846C CA 000570074 A CA000570074 A CA 000570074A CA 570074 A CA570074 A CA 570074A CA 1300846 C CA1300846 C CA 1300846C
- Authority
- CA
- Canada
- Prior art keywords
- base
- pole
- mounting structure
- ground level
- breakaway
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Abstract
ABSTRACT OF THE DISCLOSURE
A breakaway utility pole mounting structure comprising a pole (9) having an end portion (10) telescopically received in the depending tubular portion (16) of a base extending below ground level and an adhesive material (17) bond-ing said pole end portion (16) to said tubular base portion (16), said adhesive material (17) adapted to fail when said pole (10) is subjected to an impact at apredetermined distance above ground level from a vehicle of predetermined mini-mum weight moving at a predetermined minimum speed.
A breakaway utility pole mounting structure comprising a pole (9) having an end portion (10) telescopically received in the depending tubular portion (16) of a base extending below ground level and an adhesive material (17) bond-ing said pole end portion (16) to said tubular base portion (16), said adhesive material (17) adapted to fail when said pole (10) is subjected to an impact at apredetermined distance above ground level from a vehicle of predetermined mini-mum weight moving at a predetermined minimum speed.
Description
"` ~3~)~)8~
--I--BREAKAW~Y UTILITY POLE INVERTED BASE STRUCTURE
TECHNICAL FIELD
The invention relates generally to highway utility poles, and more particularly to poles for supporting lights, signs, traffic signals and the ]ike, alongside roads and highways.
BACKGROUND OF T~ INVENTION
Highway pole structures utilized on federally funded highways projects must meet the breakaway performance criteria when struck by errant vehicles in order to diminish as much as possible serious injury to the drivers of such vehicles resulting from striking such pole structures. Originally, highway poleswere wood, steel or concrete, and such poles provided such rigid resistance to impact from vehicles before breaking away that the injury to the driver was l 5 extremely severe or even fatal. Moreover, when such poles did break, not only was the driver subjected to probable further injury after impact by the broken off pole crushing the top of the vehicle, but a jagged stub was often left extend-ing above ground a substantial distance, presenting an additional hazard in the likelihood of damaging the steering or underside of the vehicle, or of crushing the vehicle and driver from the front after impact.
The present required breakaway performance criteria are set forth in the American Association of State iIighway Transportation Officials Publication entitled "Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals 1985", which states that when a standard 1800 pound vehicle (or its equivalent) travelling at 20 MPH (29.3 feet per second) strikes the luminary support at 18 inches above ground level, the speed of the vehicle is not to be reduced after break away more than 15 feet per second, and preferably not more than 10 feet per second. Another requirement is that any remaining structure after breakaway shall not extend more than four inches abovethe ~ ground level. Previously these requirements were based upon 2250 pound vehicles.
Prior pole structures for meeting the criteria witll the heavier vehicles, :
such as grooved breakaway bolts and anchorbase fittings of frangible material, have not been satisfactory when tested with ligh~er vehicles weighing a minimum of 1800 pounds.
In attempting to meet these requirements, highway utility poles have been constructed of lightweight materials such as aluminum and fiberglass, but difficulties have been encountered ~n providing poles strong enough to resist wind ,,.. ,, : , - .
. , ' . ' , ~3~30846 and weight loads while meeting the breakaway requirements, and in avoiding leaving jagged stubs extending more than 4 inches above ground after breakaway.
SUMMARY OF THE INVENTION
The present invention utilizes a novel inverted base anchored in the ground and having a tubular portion extending below ground level adapted tele-scopically to receive the bottom end portion of a utility pole, and an adhesive material bonding said end portion within the base, said adhesive material adapted to fail and release the pole upon impact upon the pole above the base by a 1 0 vehicle.
It is an object of the present invention to provide such a pole struc-ture which will break away when struck by a vehicle of required minimum weight moving at a predetermined minimum speed.
Another object is to provide such a pole structure which will cause not ~ore than a predetermined minimum reduction in vehicle speed after impact.
A further object is to provide such a pole structure which will not leave any mounting structure projecting more than four inches above ground afterimpact.
A still further object is to provide an attractive lightweight breakaway pole structure which will accomplish the foregoing objectives and provide adequate resistance to wind and weight loads.
These and other objects are accomplished by the improved pole struc-ture comprising th0 present invention, preferred embodiments of which are shown by way of example as illustrating the best known modes of carrying out the invention. Various modifications and changes in details of construction are con-templated within the scope of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a vertical cross-sect;onal view, partly in elevation, showing the bottom end of a round breakaway utility pole mounted telescopically in the novel inverted base structure;
Fig. 2 is a plan sectional view on line 2-2 of Fig. i;
Fig. 3 is a similar view showing a pole of square cross-section;
Figs. 4, 5 and 6 are schematic vertical cross-sectional views showing the progressively changing positions of the pole when breaking away due to horizontal impact by a moving force.
~ 3~846 DESCRIPTION OF PREFERRED EMBODIMENTS
The pole indicated generally at 9 is preferably tubular and it may be straight or tapered longitudinally and circular or polygonal in cross-section. It may be made from any of several materials such as steel, aluminum or other metals, or reinforced plastic such as fiberglass. It must be strong enough to resist top and wind loading, while subject to failure when tested as prescribed by the American Association of State Highway Transportation Officials publication entitled "Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals 1985". Accordingly, the more acceptable materialsfor breakaway poles are relatively lightweight such as aluminum or reinforced plastics such as fiberglass.
As shown in Fig. 1, the lower end portion I O of pole 9 is telescopically received in a base which has a peripheral flange 11 secured by nuts 12 and 13 tothe upper ends of anchor bolts 14 which are embedded in a concrete foundation 15. The base may be constructed of various materials, such as aluminum, steel, bronze or reinforced plastic. The base is inverted in the sense that its ferruleor tubular portion 1 6 depends from the base flange 11 below ground level, with the flange being substantially at or slightly below ground level and the upper nuts 12 t~o more than 4 inches above it. Accordingly, the top of the foundation 15 ispreferably spaced below ground level to allow formation of a beveled recess R
around the flange 11, facili~ating access to the anchor nuts 12 and 13. The usual design of an anchor base includes a peripheral base flange at or near ground level and a tubular ferrule extending upwardly therefrom far above the 4 inch limit to encircle the pole, which tends to cause difficulties when the pole is broken away, by leaving a stub above the maximum 4 inch projection required.
As shown, the lower end portion l O of the pole 9 is bonded to the tubular portion 16 by a thin layer 17 of adhesive material coextensive longitu-dinally with tubular portion 16, which material may be of an epoxy such as Versamid6 ' formulated to fail and release the pole when subjected to impact under the conditions prescribed previously herein. The thickness of th0 adhesive bond 17 may be from about 1/16 inch to 3/16 inch. As shown in Fig. 1, a clearance is provided between the side and bottom walls of th0 tubular portion 16 of the baseand the socket in the concrete foundation 15 which receives it, to facilitate adjusting alignmerlt of the pole to vertical.
ln the sequential depiction of stages in a test, Fig. 3 shows the position of the pole and its mounting before impact, Fig. 4 shows the conditionsat impact, and Fig. 5 shows the conditions immediately after impact as the crushed lower end of the pole is being evacuated from the inverted base.
,.. ...... . . .
~300~346 4 _ A tapered tubular fiberglass pole 9 having a square cross-section was mounted in an inverted base anchored in a concrete foundation in the ground, as shown in Fig. 1. The pole extended 24 feet above ground and had an outer cross-sectional dimension of 4-3/4 inches at the eOp with a wall 7/16 inch in thickness, and a cross-section of 6-3/4 inches immediately above the base with awall thickness of 5/16 inch. The tubular portion 16 of the base extended 6 inches below ground.
The pole 9 was tested as required by an 1800 pound weight W moving horizontally at 20 miles per hour striking the pole 18 inches above ground and the pole was crushed and evacuated from the base in the manner depicted in Figs. 4, 5 and 6. The change in velocity of the striking weight simulating that of a moving vehicle was from 30.92 feet per second before impact to 26.19 feet per second after impact, a difference of 4.13 feet per second. This result is well within the requirements of the American Association of State Highway Transporta-tion Officials; namely, speed reduction of not more than 15 feet per second, andpreferably not more than 10 feet per second. There was no projection of the remaining base structure extending more than 4 inches above ground leve!.
A pole 9' having a circular cross section and approximately the same dimensions was tested with an 8 foot long luminaire mounting arm attached to thepole 9 inches from the top. A 50 pound weight was attached to the end of the arm to simulate the mass of a luminaire. The test was performed as described in connection with square pole 9. The change in velocity of the impacting force was from 31.24 feet per second before impact to 21.29 feet per second after impact, namely 9.95 feet per second, well within the requirements.
It will be apparent that the present invention provides an improved breakaway pole mounting structure having a novel inverted base which meets the present standard specifications for highway poles and the like, and which accom-plishes the foregoing stated objectives.
--I--BREAKAW~Y UTILITY POLE INVERTED BASE STRUCTURE
TECHNICAL FIELD
The invention relates generally to highway utility poles, and more particularly to poles for supporting lights, signs, traffic signals and the ]ike, alongside roads and highways.
BACKGROUND OF T~ INVENTION
Highway pole structures utilized on federally funded highways projects must meet the breakaway performance criteria when struck by errant vehicles in order to diminish as much as possible serious injury to the drivers of such vehicles resulting from striking such pole structures. Originally, highway poleswere wood, steel or concrete, and such poles provided such rigid resistance to impact from vehicles before breaking away that the injury to the driver was l 5 extremely severe or even fatal. Moreover, when such poles did break, not only was the driver subjected to probable further injury after impact by the broken off pole crushing the top of the vehicle, but a jagged stub was often left extend-ing above ground a substantial distance, presenting an additional hazard in the likelihood of damaging the steering or underside of the vehicle, or of crushing the vehicle and driver from the front after impact.
The present required breakaway performance criteria are set forth in the American Association of State iIighway Transportation Officials Publication entitled "Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals 1985", which states that when a standard 1800 pound vehicle (or its equivalent) travelling at 20 MPH (29.3 feet per second) strikes the luminary support at 18 inches above ground level, the speed of the vehicle is not to be reduced after break away more than 15 feet per second, and preferably not more than 10 feet per second. Another requirement is that any remaining structure after breakaway shall not extend more than four inches abovethe ~ ground level. Previously these requirements were based upon 2250 pound vehicles.
Prior pole structures for meeting the criteria witll the heavier vehicles, :
such as grooved breakaway bolts and anchorbase fittings of frangible material, have not been satisfactory when tested with ligh~er vehicles weighing a minimum of 1800 pounds.
In attempting to meet these requirements, highway utility poles have been constructed of lightweight materials such as aluminum and fiberglass, but difficulties have been encountered ~n providing poles strong enough to resist wind ,,.. ,, : , - .
. , ' . ' , ~3~30846 and weight loads while meeting the breakaway requirements, and in avoiding leaving jagged stubs extending more than 4 inches above ground after breakaway.
SUMMARY OF THE INVENTION
The present invention utilizes a novel inverted base anchored in the ground and having a tubular portion extending below ground level adapted tele-scopically to receive the bottom end portion of a utility pole, and an adhesive material bonding said end portion within the base, said adhesive material adapted to fail and release the pole upon impact upon the pole above the base by a 1 0 vehicle.
It is an object of the present invention to provide such a pole struc-ture which will break away when struck by a vehicle of required minimum weight moving at a predetermined minimum speed.
Another object is to provide such a pole structure which will cause not ~ore than a predetermined minimum reduction in vehicle speed after impact.
A further object is to provide such a pole structure which will not leave any mounting structure projecting more than four inches above ground afterimpact.
A still further object is to provide an attractive lightweight breakaway pole structure which will accomplish the foregoing objectives and provide adequate resistance to wind and weight loads.
These and other objects are accomplished by the improved pole struc-ture comprising th0 present invention, preferred embodiments of which are shown by way of example as illustrating the best known modes of carrying out the invention. Various modifications and changes in details of construction are con-templated within the scope of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a vertical cross-sect;onal view, partly in elevation, showing the bottom end of a round breakaway utility pole mounted telescopically in the novel inverted base structure;
Fig. 2 is a plan sectional view on line 2-2 of Fig. i;
Fig. 3 is a similar view showing a pole of square cross-section;
Figs. 4, 5 and 6 are schematic vertical cross-sectional views showing the progressively changing positions of the pole when breaking away due to horizontal impact by a moving force.
~ 3~846 DESCRIPTION OF PREFERRED EMBODIMENTS
The pole indicated generally at 9 is preferably tubular and it may be straight or tapered longitudinally and circular or polygonal in cross-section. It may be made from any of several materials such as steel, aluminum or other metals, or reinforced plastic such as fiberglass. It must be strong enough to resist top and wind loading, while subject to failure when tested as prescribed by the American Association of State Highway Transportation Officials publication entitled "Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals 1985". Accordingly, the more acceptable materialsfor breakaway poles are relatively lightweight such as aluminum or reinforced plastics such as fiberglass.
As shown in Fig. 1, the lower end portion I O of pole 9 is telescopically received in a base which has a peripheral flange 11 secured by nuts 12 and 13 tothe upper ends of anchor bolts 14 which are embedded in a concrete foundation 15. The base may be constructed of various materials, such as aluminum, steel, bronze or reinforced plastic. The base is inverted in the sense that its ferruleor tubular portion 1 6 depends from the base flange 11 below ground level, with the flange being substantially at or slightly below ground level and the upper nuts 12 t~o more than 4 inches above it. Accordingly, the top of the foundation 15 ispreferably spaced below ground level to allow formation of a beveled recess R
around the flange 11, facili~ating access to the anchor nuts 12 and 13. The usual design of an anchor base includes a peripheral base flange at or near ground level and a tubular ferrule extending upwardly therefrom far above the 4 inch limit to encircle the pole, which tends to cause difficulties when the pole is broken away, by leaving a stub above the maximum 4 inch projection required.
As shown, the lower end portion l O of the pole 9 is bonded to the tubular portion 16 by a thin layer 17 of adhesive material coextensive longitu-dinally with tubular portion 16, which material may be of an epoxy such as Versamid6 ' formulated to fail and release the pole when subjected to impact under the conditions prescribed previously herein. The thickness of th0 adhesive bond 17 may be from about 1/16 inch to 3/16 inch. As shown in Fig. 1, a clearance is provided between the side and bottom walls of th0 tubular portion 16 of the baseand the socket in the concrete foundation 15 which receives it, to facilitate adjusting alignmerlt of the pole to vertical.
ln the sequential depiction of stages in a test, Fig. 3 shows the position of the pole and its mounting before impact, Fig. 4 shows the conditionsat impact, and Fig. 5 shows the conditions immediately after impact as the crushed lower end of the pole is being evacuated from the inverted base.
,.. ...... . . .
~300~346 4 _ A tapered tubular fiberglass pole 9 having a square cross-section was mounted in an inverted base anchored in a concrete foundation in the ground, as shown in Fig. 1. The pole extended 24 feet above ground and had an outer cross-sectional dimension of 4-3/4 inches at the eOp with a wall 7/16 inch in thickness, and a cross-section of 6-3/4 inches immediately above the base with awall thickness of 5/16 inch. The tubular portion 16 of the base extended 6 inches below ground.
The pole 9 was tested as required by an 1800 pound weight W moving horizontally at 20 miles per hour striking the pole 18 inches above ground and the pole was crushed and evacuated from the base in the manner depicted in Figs. 4, 5 and 6. The change in velocity of the striking weight simulating that of a moving vehicle was from 30.92 feet per second before impact to 26.19 feet per second after impact, a difference of 4.13 feet per second. This result is well within the requirements of the American Association of State Highway Transporta-tion Officials; namely, speed reduction of not more than 15 feet per second, andpreferably not more than 10 feet per second. There was no projection of the remaining base structure extending more than 4 inches above ground leve!.
A pole 9' having a circular cross section and approximately the same dimensions was tested with an 8 foot long luminaire mounting arm attached to thepole 9 inches from the top. A 50 pound weight was attached to the end of the arm to simulate the mass of a luminaire. The test was performed as described in connection with square pole 9. The change in velocity of the impacting force was from 31.24 feet per second before impact to 21.29 feet per second after impact, namely 9.95 feet per second, well within the requirements.
It will be apparent that the present invention provides an improved breakaway pole mounting structure having a novel inverted base which meets the present standard specifications for highway poles and the like, and which accom-plishes the foregoing stated objectives.
Claims (18)
1. A breakaway utility pole mounting structure comprising:
a utility pole having at least one substantially tubular end portion;
a base anchored in the ground substantially below ground level and having a tubular portion extending below ground level, said tubular portion adapted telescopically to enclose said pole end portion;
an adhesive material bonding said pole end portion to said base tubular portion;
said adhesive material adapted to fail when said pole is subjected to an impact at a predetermined distance above the base from a vehicle of pre-determined minimum weight moving at a predetermined minimum speed.
a utility pole having at least one substantially tubular end portion;
a base anchored in the ground substantially below ground level and having a tubular portion extending below ground level, said tubular portion adapted telescopically to enclose said pole end portion;
an adhesive material bonding said pole end portion to said base tubular portion;
said adhesive material adapted to fail when said pole is subjected to an impact at a predetermined distance above the base from a vehicle of pre-determined minimum weight moving at a predetermined minimum speed.
2. A breakaway mounting structure as in claim 1, wherein the pole end portion and the base tubular portion are substantially coextensive longitudinally.
3. A breakaway mounting structure as in claim 2, wherein the distance said base tubular portion extends below ground level is substantially equal to the diameter of said pole end portion.
4. A breakaway mounting structure as in claim 3, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
5. A breakaway mounting structure as in claim 1, wherein the distance said base tubular portion extends below ground level is substantially equal to the diameter of said pole end portion.
6. A breakaway mounting structure as in claim 5, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
7. A break-away mounting structure as in claim 6, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
8. A breakaway mounting structure as in claim 1, wherein the adhesive material is epoxy adhesive substantially one-sixteenth inch to three-sixteenth inch in thickness.
9. A breakaway mounting structure as in claim 8, wherein the pole end portion and the base tubular portion are substantially coextensive longitudinally.
10. A breakaway mounting structure as in claim 9, wherein the distance said base tubular portion extends below ground level is substantially equal to the diameter of said pole end portion.
11. A breakaway mounting structure as in claim 10, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
12. A breakaway mounting structure as in claim 11, wherein the distance said base tubular portion extends below ground level is substantially equal to the diameter of said pole end portion.
13. A breakaway mounting structure as in claim 12, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
14. A breakaway mounting structure, as in claim 13, wherein said base is adaptedto release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
15. A breakaway mounting structure as in claim 1, wherein said breakaway pole is fiberglass.
16. A breakaway mounting structure as in claim 15, wherein the pole end portion and the base tubular portion are substantially coextensive longitudinally.
17. A breakaway mounting structure as in claim 16, wherein the distance said base tubular portion extends below ground level is substantially equal to the diameter of said pole end portion.
18. A breakaway mounting structure as in claim 17, wherein said base is adapted to release said pole upon failure of said adhesive, leaving a remaining base structure projecting no more than 4 inches above ground level.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16553088A | 1988-03-08 | 1988-03-08 | |
| US165,530 | 1988-03-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1300846C true CA1300846C (en) | 1992-05-19 |
Family
ID=22599290
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000570074A Expired - Fee Related CA1300846C (en) | 1988-03-08 | 1988-06-22 | Breakaway utility pole inverted base structure |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1300846C (en) |
-
1988
- 1988-06-22 CA CA000570074A patent/CA1300846C/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |