The present invention is related to roadway barriers and safety systems, and more particularly, to cable guardrail systems.
Along many roadways it may be hazardous for a vehicle to leave the roadway. As a result, safety barriers, including guardrail systems, are used along roadways. The guardrail systems may act to contain and redirect an errant vehicle along such roadways. Such guardrail systems may dissipate some of the vehicle's energy. One such guardrail system is a cable guardrail system. Cable guardrail systems may reduce the damage caused to impacting vehicles and the injury to vehicle passengers. Compared with W-beam and three beam guardrail systems, cable guardrail systems are often more aesthetically appealing and may increase motorist sight distance. Cable guardrail systems also may reduce snow accumulation on adjacent highways and roadways.
A cable guardrail system in the past may have included a plurality of cables secured to a plurality of support posts. Various types of cables and wire ropes have been satisfactorily used for cable guardrail systems. Support posts have been made of wood, metal, or a combination of both. Additionally, cable guardrail systems have included cable anchors that fixed the end of the cables to the ground to maintain tension in the cables. Various types of anchor systems have been used including releasable anchors as described in U.S. Pat. No. 6,065,738 to Pearce.
The number of cables in prior cable guardrail systems has varied depending on factors such as the types of vehicles using the roadway and the types of hazards requiring the guardrail system. Cables have been attached to support posts using various attachment mechanisms. Some attachment mechanisms, such as hook-bolts, were used to attach a single cable to a support post. Another prior attachment mechanism attached three cables to one side of a support post as shown in U.S. Pat. Nos. 7,398,960 and 7,364,137 to Neusch. Other cable guardrail systems positioned cables on opposite sides of the support posts in order to protect against impact from either side such as might occur when the system was installed in a highway median.
The state of the art in cable guardrail systems has been documented and applied through specifications used by the industry. The United States Department of Transportation Federal Highway Administration provides “Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects,” including a section for cable guardrail systems and attachment mechanisms. Industry groups such as the American Association of State Highway and Transportation Officials (AASHTO), the Associated General Contractors (AGC) of America, and the American Road & Transportation Builders Association (ARTBA) have developed “A Guide to Standardized Highway Barrier Hardware” that included specifications for cable guardrails and posts. These specifications teach a cable guardrail system having a cable attached by hook-bolts and nuts to one side of a flanged-channel post. Additionally, agencies in both the United States and Europe have established guidelines for impact testing of safety barrier systems.
Prior cable guardrail systems had several drawbacks. Some cable attachments were difficult or costly to manufacture and install. Installation of cable guardrail systems exposes installation personnel to risks associated with working on or near active highways and roadways. Cable guardrail systems have been developed that reduce installation time thereby reducing the risk faced by installation personnel. There continues to be a need, however, for cable guardrail systems that reduce installation time and cost, and reduce risk to personnel.
A hanger for a cable guardrail system capable of supporting at least two cables traverse a post is presently disclosed to dissipate a portion of an impacting vehicle's energy and enable an impacting vehicle to be redirected by the system. The cable guardrail system may be installed adjacent a roadway, such as along median strips, roadway shoulders, or any other path that is likely to encounter vehicular traffic.
The disclosed hanger comprises a first portion having first and second seats each capable of supporting a cable, with the first and second seats on opposite sides of a post, and a second portion capable of engaging the end of the post.
Additionally, the disclosed cable guardrail system may comprise a plurality of posts capable of supporting at least two cables traverse the posts, a plurality of hangers attached to at least a portion of the plurality of posts, and at least two cables supported by the first and second seats on opposite sides of the posts.
Presently contemplated embodiments of the present guardrail system are described below by reference to the following figures:
Referring generally to
When the cable guardrail system 10 is installed along the side of a roadway, the system is capable of dissipating a portion of an impacting vehicle's energy and redirecting the impacting vehicle along the general direction of the roadway. As the vehicle impacts the cable guardrail system 10, the cables 11 and support posts 30 may deflect from the installed position. The deflection of the cables 11 and the support posts 30 may dissipate a portion of the vehicle's impact energy. Additionally, forces from the vehicle impacting against the cables may cause the hanger 20 to move relative to the support post 30. As a result, the cables 11 may maintain contact with the impacting vehicle dampening yaw, pitch, and roll of the impacting vehicle.
The cables 11 may be a 3×7 wire rope, as shown in
The hanger 20 shown in
The seats 22 may be formed in multiple ways. The seats 22 may be formed as an integral part of the first portion 21. Alternatively, the seats 22 may be formed as separate pieces and attached to the first portion 21, such as, but not limited to, by welding, crimping, fastening, interlocking, or another suitable attachment technique.
The second portion 25 of the hanger is capable of engaging the end of the post 30. The second portion 25 may be generally U-shaped as shown in
The first portion 21 and the second portion 25 may be formed together out of one piece of material, such as shown in
The hanger 20 may be formed from steel, in the form of sheet, bar stock, tube stock, or wire stock. Alternatively, the hanger 20 may be formed from other metal or non-metal materials of suitable strength. The hanger may be formed from steel of spring and/or other suitable specifications. Additionally, the hanger 20 may have a coating to provide durability and protection against rusting in addition to engagement enhancement. The hanger 20 may be hot-dip coated with zinc, aluminum, zinc-aluminum alloy or other coating to provide protection against the elements. Alternately, the hanger 20 may be coated with a polymer or other paint coating for a protection against the environment.
Other hanger configurations are also contemplated. As shown in
A further alternative hanger is depicted in
During installation or maintenance of a cable guardrail system 10, the second portion 25 of the hanger 20 may slideably engage the end of the post 30 in a top-down installation. A first cable and a second cable may then be attached to the hanger 20 on opposite sides of the post. Such an installation may be faster and more efficient than installation of prior cable attachment mechanisms. Faster installations are less costly and reduce the time that installation personnel are exposed to the hazards associated with working alongside roadways. Further, maintenance of a cable guardrail system 10 may be improved because the hanger 20 may be removed and reattached.
Alternatively, a hanger 20 may be attached to a first cable and a second cable, then attached to a post 30. The second portion 25 of the hanger 20 may then slideably engage the end of the post 30 in a top-down installation. By first attaching the hanger to the cables, the cables may assist in installing the hanger 20 over the end of the post.
As shown in
The clip 50 may be formed from steel, in the form of sheet, bar stock, tube stock, or wire stock. Alternatively, the clip 50 may be formed from other metal or non-metal materials of suitable strength. The clip may be formed from steel of spring and/or other suitable specifications. Additionally, the clip 50 may have a coating to provide durability and protection against rusting and other environment conditions. The clip 50 may be hot-dip coated with zinc, aluminum, zinc-aluminum alloy or other coating to provide protection against the elements. Alternately, the clip 50 may be coated with a polymer or other paint coating.
As shown in
The cable guardrail system 10, as shown in
When an errant vehicle impacts the cable guardrail system 10, the post 30 and cables 11 at the point of impact may deflect from the installed position. As the defection increases, the hanger 20 may release from the post 30 so that the cables 11 may remain in substantial contact with the errant vehicle. Friction enhancing surfaces on the second portion 25 of the hanger 20 or on the post 30 may increase the energy dissipated as the hanger 20 separates from the post 30. As the cables 11 release from the posts 30, the overall deflection may increase. The spacing of posts 30 and cable anchors (not shown) may be adjusted to maintain the desired deflection of the cable guardrail system 10 during a vehicle impact.
As shown in
The support post 30 may be constructed of plain carbon steel having carbon content between about 0.4% and 1.0% by weight. Alternately, the plain carbon steel of the support post 30 may have carbon content in a range between about 0.69% and 0.75% by weight. The support post material may have yield strength between about 60,000 lbs/in2 and about 100,000 lbs/in2, and a tensile strength greater than about 80,000 lbs/in2. Alternately, the support post 30 may have a yield strength greater than about 60,000 lbs/in2 and a tensile strength greater than about 90,000 lbs/in2. The yield strength may allow the support post 30 to provide sufficient support to resist the vehicle impact forces associated with an impact, and may then fracture to allow more energy to be absorbed.
The support post 30 may have a weight between about 2 and 7 pounds per foot of post length (between about 2.9 and 10.4 kilograms per meter). Alternatively, the weight of the support post 30 may be about 5 pounds per foot of post length (about 7.4 kilograms per meter). Prior steel support posts typically featured a weight of 8 pounds per foot of post length (about 11.9 kilograms per meter) or greater. Although these heavier support posts may be used, the support post 30 of the present disclosure may reduce the weight of the support posts and the accompanying cost of the posts.
By way of example, and not limitation, the support post 30 may be formed from U.S. new-billet steel, rail steel, or other types of steel alloys or other materials with the desired strength for the cable guardrail system 10. Further, the support post 30 may have a coating of polyester to provide durability and protection against rusting. Alternatively, the support post 30 may be hot-dip coated with zinc, aluminum, chromate, zinc-aluminum alloy or other coating to provide protection against the elements.
Installation of the support posts 30 may be completed using various techniques which are well known in the art. The particular technique used may depend upon the type of soil conditions and other factors associated with the roadway, and the type of road and other hazards involved in installation of the cable guardrail system 10. The support posts 30 may be installed with or without the use of metal foundation tubes or a concrete foundation.
While the invention has been described with detailed reference to one or more embodiments, the disclosure is to be considered as illustrative and not restrictive. Modifications and alterations will occur to those skilled in the art upon a reading and understanding of this specification. It is intended to include all such modifications and alterations in so far as they come within the scope of the claims, or the equivalents thereof.
This application claims priority to U.S. provisional patent application Ser. No. 61/027,314, filed on Feb. 8, 2008, the disclosure of which is incorporated herein by reference.
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