Patent Application
20090272956
The present invention relates generally to safety treatment for the ends of W-beam guardrails; and more particularly, to a tensioned guardrail terminal for dissipating impact energy of a car colliding with the end of the W-beam guardrail in an end-on or re-directive impact.
Along most highways there are hazards that can be a substantial danger to drivers of automobiles if the automobiles leave the highway. To reduce the severity of accidents due to vehicles leaving a highway, guardrails are provided. The guardrails are installed such that the beam elements are in tension to aid in re-directive type impacts. Guardrails must be installed, however, such that the terminal end of the guardrail facing the flow of traffic is not a hazard. Early guardrails had no proper termination at the ends, and it was not uncommon for impacting vehicles to become impaled on the guardrail causing intense deceleration of the vehicle and severe injury to the occupants. In some reported cases, the guardrail penetrated directly, into the occupant compartment of the vehicle fatally injuring the occupants.
Upon recognition of the problem of proper guardrail termination, guardrail designs were developed that used box beams and W-beams that allow tapering of the end of the guardrail into the ground. Such designs eliminate any spearing effect. While these end treatments successfully removed the danger of the vehicle being penetrated in a head-on collision, it was discovered that these end treatments operate in a ramp-like fashion and may induce launching of the vehicle causing it to become airborne for a considerable distance with the possibility of roll over.
In search for better end treatments, improved energy absorbing end treatments for W-beam guardrail elements were developed. For example, an extruder terminal was developed and typically includes a bending structure that squeezes the guardrail into a flat plate and then bends it about a circular arc directed away from the impacting vehicle. Example extruder terminal products include the ET 2000™ and the ET-PLUS™ offered by Trinity Highway Products. Other extruder terminal products include the SKT 350™ and FLEAT 350™ offered by Road Systems, Inc.
All of these energy absorbing systems use a cable to connect the first w-beam guardrail segment to the first post in the system. The cable provides tension in the guardrail beam element for a redirective hit along the length-of-need portion of the guardrail. A number of cable releasing posts have also been developed for use in these terminals. The cable release posts are intended to release the cable anchor and, thus, release the tension in the system when the post is impacted in either of a forward (end-on) or reverse direction. Such systems are not able to remain in tension during end-on and reverse-direction type impacts.
The present invention provides a new and improved end treatment for highway guardrails.
In accordance with a particular embodiment of the present invention, an end treatment of a guardrail safety system includes a terminal portion of a guardrail beam that has a downstream end and an upstream end. The terminal portion of the guardrail beam slopes from a first vertical height appropriate for redirecting an errant vehicle to a second vertical height proximate the surface of the ground at an upstream end of the terminal portion of the guardrail beam. A flattening portion forms a channel through which the terminal portion of the guardrail beam is disposed. A vertical dimension of the channel is greater at a downstream end of the flattening portion than at an upstream end of the flattening portion. An impact plate is connected to the flattening portion for engaging an impacting vehicle at an end of said guardrail beam. During an end-on impact, the impact plate and the flattening portion are advanced longitudinally along the guardrail in a downstream direction by the vehicle. The advancement of the impact plate and flattening portion dissipate energy to decelerate the impacting vehicle. As downstream portions of the guardrail beam are forced into the flattening portion, the guardrail is flattened vertically
Technical advantages of particular embodiments of the present invention include a guardrail end treatment that dissipates impact energy through the compression of a W-beam guardrail element. Thus, one advantage may be that the guardrail end treatment is energy absorbing. Another advantage may be that the end treatment forces the W-beam guardrail element through a flattening structure that squeezes the guardrail into a relatively flat plate. Specifically, the guardrail end treatment may dissipate impact energy of a vehicle colliding with an end of a guardrail by flattening a portion of the guardrail.
Still another advantage may be that an end of the W-beam guardrail element extends through the flattening structure and tapers to the ground. The W-beam guardrail element may be secured to the ground in tension. The components of the system that provide the tensile connection of the guardrail beam to the terminal support post may enable the guardrail beam to remain secured after an end-on or re-directive impact. Thus, the system may remain in tension during both types of impacts. Still another advantage may be that the tension is released when the system is impacted in the reverse direction near the terminal end, however. The releasing of tension in the guardrail element for reverse direction impacts prevents vehicle instability and excessive deceleration.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.
Existing guardrail end treatments have proven to be unsafe for some collision conditions that happen on the highway, sensitive to installation details, and/or very costly. However, the end treatment described below is a safety treatment for the ends of a W-beam guardrail that provides a higher level of performance over a wider range of collision conditions and reduces end treatment costs and the number of injuries and deaths associated with guardrail terminal accidents. The described system maintains the tension in the guardrail beam element during both end-on and re-directive type impacts. When the system is impacted in the reverse direction near the terminal end, however, the anchorage system may release to prevent vehicle instability or excessive deceleration.
Guardrail system 100 includes a guardrail beam 102 and support posts 104 that anchor guardrail beam 102 in place along the roadway. In a particular embodiment, guardrail beam 102 may include multiple 12-gauge W-beam rail elements of a length on the order of approximately 12.5 feet or 25 feet. The guardrail beam sections may be mounted at a height of on the order of approximately 27 to 31 inches with rail splices positioned mid-span between the support posts 104. Guardrail beam 102 and the terminal end of guardrail beam 102, specifically, are illustrated in more detail in
Guardrail beam 102 is attached to support posts 104 with connectors that may include, in particular embodiments, slotted countersunk bolts such as, for example, 16 mm (⅝-inch) diameter by 38 mm (1½-inch) long flat slot machine screws. Oversized guardrail nuts may be used on the back side of the support post 104. Support posts 104 may be embedded in the ground, a concrete footing, or a metal socket. Support posts 104 may be made of wood, metal, plastic, composite materials, or any combination of these or other suitable materials. It is also recognized that each support post 104 within guardrail system 100 need not necessarily be made of the same material or include the same structural features. Furthermore, the cross-section of support posts 104 may be any engineered shape suitable for releasably supporting guardrail beam 102. Such cross-sectional shapes may include, but are not limited to, square, rectangular, round, elliptical, trapezoidal, solid, hollow, closed, or open.
Guardrail system 100 is intended to keep errant vehicles from leaving the roadway during a crash or other hazardous situation. In many instances, guardrail 100 is installed between a roadway and a significant hazard to vehicles (e.g., another roadway, a bridge, cliff, etc.). Therefore, guardrail system 100 should be designed to withstand a significant impact from a direction generally perpendicular to the roadway, without substantial failure. It is this strength that allows guardrail system 100 to withstand the impact, and still redirect the vehicle so that it is once again traveling generally in the direction of the roadway.
However, testing and experience has continuously shown that guardrail systems may actually introduce additional hazards to the roadway and surrounding areas. This is particularly true with respect to vehicles that impact the guardrail system adjacent its terminal section, in a direction generally parallel to the roadway. For example, if the guardrail system were rigidly fixed in place during a crash, serious injury and damage may result to the errant vehicle, its driver and passengers. Accordingly, many attempts have been made to minimize this added risk. Such methods generally include the use of terminal portions that are tapered from the ground up to effectively reduce the impact of head on collisions and to create a ramp-like effect that causes vehicles to go airborne during a crash. Other methods include breakaway cable terminals (BCT), vehicle attenuating terminals (VAT), SENTRE end treatments, breakaway end terminals (BET) and the breakaway support posts of U.S. Pat. No. 6,398,192 (“'192 Patent”). Many-such terminals, supports, end treatments and the like are commercially available from various organizations. Examples include the HBA post by Exodyne Technologies and Trinity Industries, and a breakaway support post similar in configuration to that described in the '192 Patent.
Referring again to
Although
Terminal section 108 may be installed either parallel to the roadway or at an angular departure from the roadway, as shown best in
In a particular embodiment where terminal section 108 is linearly flared, terminal section 108 may be flared back at an angle of approximately 6 to 7 degrees from the non-terminal portion of the guardrail. Where support posts 104 of terminal section 108 are spaced apart at intervals of approximately 75 inches, the most downstream post 104 of terminal section 108 may be approximately 9 inches offset from a line tangent to the non-terminal portion of the guardrail, in a particular embodiment. Moving toward the upstream end of terminal section 108, the next four successive support posts 104 may be 19, 29.25, 39, and 48 inches offset from a line tangent to the non-terminal portion of the guardrail, in this embodiment. Terminal post 106, which may be positioned directly below guardrail beam 102, may be approximately 47 inches offset from a line tangent to the non-terminal portion of the guardrail, in the described embodiment.
As shown better in
Guardrail beam element 102 feeds into an inlet 116 at a downstream end of flattening chute 112. Guardrail beam element 102 is disposed within flattening chute 112 and extends the length of flattening chute 112. Guardrail beam element 102 exits an outlet 118 at an upstream end of flattening chute 112. As will be described in more detail with regard to
A terminal post 106 secures the terminal end of guardrail beam element 102 to the ground and places guardrail beam element 102 in tension. As will be described in more detail with regard to
The vertical distance between channel members 122 and 124 is an appropriate distance such that guardrail beam 102 is inserted into the channel created by extruder 120. For example, where guardrail beam 102 comprises a 12-gauge W-beam rail element having a vertical dimension of approximately 12.25 inches, the distance between the top of channel member 122 and the bottom of channel 124 may be approximately 14 inches, in a particular embodiment.
Front striking plate 114 is secured by welding to extruder 120 of end treatment 110. Front striking plate 114 may be vertically elongated, in particular embodiments. Thus, front striking plate 114 may extend both above and below extruder 120 to permit front striking plate 114 to be easily engaged by either the high bumper of trucks, SUV's, and other taller vehicles and the low set bumpers of smaller cars impacting in a frontal manner. Front striking plate 114 is also positioned so as to engage the vehicle frame or rocker panel to reduce vehicle intrusion when the upstream end of end treatment 110 is impacted by a vehicle in a sideways manner.
Flattening portion 112, which is mounted to extruder 120, may be constructed from four metal plates, in a particular embodiment. The four metal plates may be cut and/or bent and then welded together to form the desired configuration. Alternatively, flattening portion 112 may be formed from more than four pieces or from a single piece of metal that is cut and bent into the desired configuration. When flattening portion 112 is assembled, flattening portion 112 may form an enclosed structure that houses a terminal portion of guardrail beam 102.
In the illustrated embodiment, flattening portion 112 includes three sections. The most downstream portion of flattening portion 112 includes a throat 128. The vertical dimension of throat 128 is greater at the downstream end and decreases as it approaches the upstream end of end treatment 110. For example, in a particular embodiment, the vertical dimension of throat 128 may be approximately 14 inches wide at the downstream end and approximately 4.5 inches wide at the upstream end. The horizontal length of throat 128 may be within a range of approximately 11 to 13 inches.
In a particular embodiment, the slope of a lower edge 132 may be greater than the slope of an upper edge 130. The increased slope of lower edge 132 may aid in the flattening of guardrail beam 102 during an impact. For example, in a particular embodiment, upper edge 130 may slope upward at an angle of approximately 11 degrees from the horizontal, and lower edge 132 may slope downward at an angle of approximately 13 degrees from the horizontal. In still other embodiments, the slope of upper edge 130 and lower edge 132 may be substantially the same. Thus, in a particular embodiment, upper edge 130 and lower edge 132 may symmetrically mirror one another. In still other embodiments, one of top edge 130 and lower edge 132 may be aligned with the horizontal (substantially parallel with the roadway) while the other of top edge 130 and lower edge 132 slopes upward or downward, respectively.
A mid portion 134 extends from the upstream end of throat 128 and slopes toward the ground. Specifically, mid portion 134 is configured to transition guardrail beam element 102 from a height above the ground level that is appropriate for redirecting an impacting vehicle (31 inches, in a particular embodiment) to a height that is proximate the ground's surface. Thus, mid portion 134 extends from a vertical distance associated with throat 128 at a downstream end to approximately ground level at an upstream end. In a particular embodiment, where the horizontal length of mid portion 134 is approximately 18.75 inches, mid portion 134 may slope at an angle of approximately 38 degrees from the horizontal.
Mid portion 134 also provides a channel through which a terminal portion of guardrail beam element 102 is disposed. In a particular embodiment, the vertical dimension of the channel within mid portion 134 may be approximately 4.5 inches (similar to the width of throat 128 at the upstream end). The dimensions of the channel within mid portion 134 may remain substantially constant such that the vertical dimension of the channel within mid portion 134 at the downstream end is the substantially the same as the vertical dimension of the channel within mid portion 134 at the upstream end.
A third portion of flattening portion 112 includes outlet portion 136. Outlet portion 136 extends from the upstream end of mid portion 134. Outlet portion 136 is disposed proximate the grounds' surface and is in substantial alignment with the grounds' surface. Outlet portion 136 also forms a channel through which the terminal end of guardrail beam element 102 exits the flattening chute 112. In a particular embodiment, the vertical dimension of the channel within outlet portion 136 may be approximately 4.5 inches (similar to the vertical dimension of the channel within mid portion 134). The dimensions of the channel within outlet portion 136 may remain substantially constant such that the vertical dimension of the channel at the downstream end of outlet portion 136 is substantially the same as the vertical dimension of the channel at the upstream end of outlet portion 136. In a particular embodiment, the horizontal length of outlet portion 136 may be approximately 5-7 inches.
As stated above with regard to
During an end-on or oblique end-on collision of a vehicle with front striking plate 114, end treatment 110 may be displaced in a downstream direction and downstream portions of guardrail beam element 102 may be forced into the displaced end treatment 110. During such a collision, extruder 120 functions as a guide to guide guardrail beam element into flattening portion 112. Extruder 120 includes guides 138 that prevent shaving of the W-beam guardrail element 102 by ends of extruder 120 as extruder 120 moves along the length of the guardrail beam element 102 during a collision. The guides 138 accommodate any irregularities or bumps in guardrail beam element 102 to ensure proper feeding of guardrail beam element 102 into flattening portion 112.
As end treatment 110 moves along guardrail beam element 102 and downstream portions of guardrail beam element 102 are forced into flattening portion 112, guardrail beam element 102 is flattened vertically. Portions of guardrail beam element 102 exiting outlet 118 of flattening portion 112 are flattened into what may appear to be four vertically stacked plates. For example, where the vertical dimension of guardrail beam element 102 is approximately 12.25 inches and throat portion 134 of flattening portion 112 is approximately 4.5 inches, the vertical dimension of the flattened portion of guardrail beam element 102 may be less than approximately 4.5 inches. As this flattening process occurs, substantial energy is dissipated slowing the impacting vehicle.
To aid in initial flattening of guardrail beam element 102 for coupling to terminal support post 106, a terminal end of guardrail beam element 102 may be modified.
Slotted zone 202 may initiate at a terminal end 203 of guardrail beam element 200 and extend a desired distance downstream. The horizontal length of slotted zone 202 may vary depending on the horizontal length of end treatment 110. It may be desirable for slotted zone 202 to include the portion of guardrail beam element 200 that is coupled to terminal post 106 and the portion of guardrail beam element 200 that traverses through flattening portion 112. Generally, slotted zone 202 may extend from the terminal, upstream end of guardrail beam element 200 to some distance between the first and second support posts 104. Where, for example, the dimensions of the terminal section 108 of guardrail system 100 are similar to those illustrated in
The placement of the slots in slotted zone 202, according to a particular embodiment, may be better understood with reference to the cross-section for a typical W-beam guardrail 200 as shown in
Slots 212 and 214 should be of a size sufficient to enhance the ability of the terminal end of guardrail beam element 200 to be flattened. In a preferred embodiment, the entire vertical dimension of each peak 206 and valley 204 may be removed. Effective sizes for slots 212 have been found to be approximately 0.5 inches, as measured vertically. An effective size for slot 214 has been found to be approximately 0.75 inches, as measured vertically. Thus, in a particular embodiment, slots 212 may have a width on the order of 0.5 inches and extend approximately 81-82 inches. Slot 214 may have a width on the order of approximately 0.75 inches and extend approximately 81-82 inches. The provided dimensions are for example purposes only, however. Any dimensions may be used for slots 212 and 214 to enhance the ability of guardrail beam 200 to be flattened into four vertically stacked plates throughout the terminal end of guardrail beam element 200.
While guardrail beam 102 may include W-beam rail elements, it is generally recognized that the illustrated guardrail beam 102 is merely an example of a beam that may be used in a guardrail system. Guardrail beams 102 or portions of guardrail beams 102 may include conventional W-beam guardrails, thrie beam guardrails, box beams, wire ropes, or other structural members suitable for redirecting an errant vehicle upon impact. It is also recognized that the configuration and dimensions of any of the above-described elements within guardrail system 100 may vary as desired.
Returning to
The tension in guardrail beam 102 may also be retained in this manner when guardrail system 100 is subject to a re-directive impact in the length of need portion of guardrail system 100. For example, when an impacting vehicle traveling in a direction substantially parallel to the downstream direction of guardrail system 100 leaves the roadway and impacts guardrail system 100, any support posts 104 impacted by the vehicle may operate to release guardrail beam element 102 as they are impacted. Modified support posts 104 may be bent toward the ground such that the support posts 104 are displaced and do not pose a hazard to the impacting vehicle. Because the tension in guardrail beam 102 is maintained, guardrail beam element 102 continues to operate to redirect the vehicle back onto the roadway even after one or more support posts are released from guardrail beam element 102.
As illustrated, support posts 500, 600, and 700 include elongate, continuous structural members and are each of a standard wide flange configuration. Each support post includes two flanges 502, that are generally parallel with one another, and in spaced apart relation from one another. A web 504 forms the coupling between flanges 502. In a preferred embodiment, flanges 502 include a generally identical configuration of boltholes 506 and cutouts 508, therein.
With regard to the wide flange shape used as a guardrail post, the cross section is typically shaped like the letter “H”. The cross section has two major axes for bending. The “weak” axis generally refers to a central axis that extends through the web and is perpendicular to the flanges. The “strong” axis generally refers to a central axis that is perpendicular to the web and parallel to the planes of the flanges. The weak axis for a conventional installation of guardrail extends generally transversely to the road. The strong axis extends generally along the roadway.
In the illustrated embodiment of
Support posts 500, 600, and 700 have a length in a range of approximately 72 and 73⅜ inches, in particular embodiments, and include an upper portion 510 and a lower portion 512. A mid portion 514 couples upper portion 510 with lower portion 512. Upper portion 510 includes two boltholes 506 that are adapted to receive connectors for the installation of a guardrail beam (e.g., guardrail beam 102) upon the support post. Lower portion 512 is suitable for installation below grade, as part of a guardrail support system.
Bolt holes 506 include a standard configuration that allow for the installation of widely used guardrail beams, upon the respective support post. In general, bolt holes 506 align with the center of the guardrail beam, and maintain the center of the guardrail beam approximately 30 inches above grade. However, the number, size, location and configuration of boltholes 506 may be significantly modified, within the teachings of the present invention.
Support posts 500 and 600 are each modified to include a relatively “weak” axis W, and a relatively “strong” axis S. Support posts 500 and 600 are normally installed along a roadway such that weak axis W is generally perpendicular to the direction of traffic, and strong axis S is generally parallel to the direction of traffic. Accordingly, support posts 500 and 600 are typically able to withstand a significant impact (e.g., with a car traveling at a high rate of speed) about the strong axis S without substantial failure. However, support posts 500 and 600 are intentionally designed such that failure will more readily occur in response to an impact about the weak axis W. Stated differently, support posts 500 and 600 exhibit adequate strength in the lateral direction but sufficiently low strength in the longitudinal direction. Accordingly, if a vehicle impacts end treatment 110 “end-on”, support posts 500 and 600 will tend to fail (e.g., buckle), while allowing the vehicle to decelerate as it impacts consecutive support posts. However, if a vehicle strikes guardrail system 100 along the face of and at an angle to guardrail beam 102, support posts 500 and 600 will provide sufficient resistance (strength) to redirect the vehicle along a path generally parallel with guardrail beam 102.
Mid portions 514 of support posts 500 and 600 include two cutouts 508, which are configured to further weaken the support posts about the weak axis W, to more readily allow for failure due to impact from a vehicle along that direction. Cutouts 508 are positioned within mid portion 514 to weaken the support posts about weak axis W, adjacent grade (when installed). This will accommodate failure of the support posts approximately at grade, allowing support posts 500 and 600 to “fold” over from the point of failure, upward. Since lower portion 512 is below grade, it is not expected that the ground, or lower portion 512 of the support post will appreciably deflect during an impact.
Since cutouts 508 are intended to occur approximately at grade, and the center of bolt holes 506 are intended to occur 30 inches above grade, bolt holes 506 occur 30 inches above cutouts 508, in the illustrated embodiment. It will be recognized by those of ordinary skill in the art that the size, configuration, location and number of bolt holes, cutouts, and their relationship with each other, may be varied significantly within the teachings of the present invention. The overall length of the support posts, and their respective upper, lower and mid portions may vary significantly, within the teachings of the present invention. For example, in other embodiments, cutouts 508 may occur below grade or above grade. The depth of cutouts 508 below grade should not exceed an amount that will prevent the support posts from failing at or near the location of cutouts 508. At some depth below grade, the surrounding earthen (or other) material will reinforce lower portion 512 of the support posts to an extent that will no longer accommodate such failure to occur.
The height of cutouts 508 above grade should not exceed a point at which the support post will fail at cutouts 508, and leave a “stub” above grade which can snag vehicles, and otherwise cause excessive injury and/or excessive damage. Such a stub could be detrimental to the redirective effect of the guardrail system in which the support post is operating.
The vertical dimension of a cutout 508 is limited based upon the horizontal dimension of cutout 508. For example, a ratio of the vertical dimension of any particular cutout may be equal to, or less than three times the horizontal dimension. Alternatively, the ratio may be limited to two times the horizontal dimension. In the illustrated embodiments, the ratio is 1:1, since cutout 508 is generally a circular opening in the support post. The smaller the vertical dimension of the cutout, the more precisely the designer may dictate the point of failure along the vertical length of support posts 500 and 600.
Various configurations of cutouts 508 are available to a designer of support posts 500 and 600, in accordance with the teachings of the present invention. For example, rather than circular openings, cutouts 508 may comprise square, rectangular, triangular, oval, diamond shaped, or practically any other geometric configuration, and still obtain some or all of the benefits described herein.
The horizontal orientation of cutouts 508 within flanges 502 may also be altered significantly, within the teachings of the present invention. In the illustrated embodiments of
Alternatively, a sawcut could be employed from the outer edge of the flange, and extending inward, to form cutouts 508. In this manner, the sawcut would form the starting point of the likely point of failure along the weak axis of the support post. Rather than a sawcut, a similar configuration may include a slot in which the longest dimension extends horizontally through the flange. Such a slot may begin or terminate at the edge of the flange, or otherwise be disposed completely within the material of the flange.
As stated above,
Although W6×8.5 wide flanges are described above and illustrated within this specification, it should be recognized by those of ordinary skill in the art that practically any size guardrail support post may be weakened as described above. The size, weight and configuration of the support post are just a few factors to be considered to determine the appropriate location of cutouts, to allow yielding along the weak axis while maintaining sufficient strength along the strong axis to redirect impacting vehicles. Further, although it may be desirable for at least a portion of the support posts in the guardrail safety system 100 to include weakened support posts such as support posts 500 and 600 of
Although certain of the support posts may be configured to release the guardrail beam element upon vehicular impact, it may be desirable for a terminal support post to remain coupled to guardrail beam even after an end-on or re-directive impact.
In particular embodiments, terminal support post 800 is releasably coupled to guardrail beam 102 such that guardrail beam 102 and provides positive anchorage of guardrail beam 102 to react to tensile loads on guardrail beam 102 to redirect a vehicle impacting laterally along the length of guardrail beam 102. Various components are used to effect the coupling of guardrail beam 102 to terminal support post 800 such that guardrail beam 102 remains coupled to terminal support post 800 when guardrail system 100 is struck by an impacting vehicle in an end-on or re-directive type impact. As a result, guardrail beam element remains supported in tension even after such an impact. However, when guardrail system 100 is struck by an impacting vehicle in the reverse direction, the tensile coupling of guardrail beam 102 will be released from terminal support post 800 to prevent vehicle instability and excessive vehicular deceleration.
In the illustrated embodiment, terminal support post 800 includes a structural member 802 of an I-beam configuration. Structural member 802 includes a pair of flanges 804 interconnected by a central web 806. In a currently preferred embodiment, the beam member 802 comprises a W 6×15 steel post member. A pair of rectangular side plates 808 are affixed opposite sides of structural member 802. Preferably, side plates 808 are secured by welding to each of flanges 804.
A connector assembly is used to couple structural member 802 to the guardrail beam member. The connector assembly is configured such that the coupling of the structural member and the terminal portion of the guardrail beam is maintained during an end-on or re-directive impact by a vehicle. However, the connector assembly is configured to release the coupling during a reverse-direction impact. In a particular embodiment, the connector assembly comprises a plurality of stacked rectangular plates that are aligned to receive the terminal portion of the guardrail beam. For example, the connector assembly may include a stack of three plates: a flange plate 810, a keeper plate 816, and a washer plate 824.
A flange plate 810 is secured between side plates 808. Flange plate 810 is preferably a unitarily formed piece that is secured by welding to structural member 802 and each side plate 808. Flange plate 810, as best shown in
V-shaped slot 812 is centered along the horizontal width of flange plate 810 and has a vertical length of approximately 1 inch and a horizontal width of approximately 1¾ inches. The rounded bottom 814 of V-shaped slot 812 has a diameter of approximately 1¼ inches. However, the described and depicted dimensions of flange plate 810 are provided for example purposes only. Although the depicted dimensions may be appropriate where structural member 802 includes a W 6×15 steel post member, the dimensions of flange plate 810 may vary and may depend on size and dimensions of structural member 802.
Returning to
Returning to
U-shaped slot 826 is centered along the horizontal width of washer plate 824 and has a vertical length of approximately 1¼ inches and a horizontal width of approximately 1⅛ inches. The rounded bottom slot 826 has a diameter of approximately 1¼ inches. However, the described and depicted dimensions of washer plate 824 are provided for example purposes only. Although the depicted dimensions may be appropriate where structural member 802 includes a W 6×15 steel post member, the dimensions of washer plate 824 may vary and may depend on size and dimensions of structural member 802.
Each of flange plate 810, keeper plate 816, and washer plate 824 include a pair of boltholes 830. In the illustrated embodiments, boltholes 830 are approximately ⅜ inches in diameter. When assembled together, a bolthole 830 of each of flange plate 810, keeper plate 816, and washer plate 824 are in general alignment with one another. A pair of threaded bolts 832 may be secured through boltholes 830 to secure flange plate 810, keeper plate 816, and washer plate 824 together. A washer 834 may be threaded onto the end of each of the threaded bolts 832 to hold the plates relative to each other.
As described above, the purpose of terminal support post 800 is to secure guardrail beam 102 in tension.
In the illustrated embodiment, connection plate 1002 includes a pair of boltholes 1004, which may be aligned with a pair of similar boltholes (not shown) in the terminal end of the compressed slotted guardrail beam 1000. A pair of threaded bolts 1006 may be threaded through boltholes 1004 and similarly sized boltholes of guardrail beam 1000 (not shown) that are aligned with boltholes 1004. A threaded nut 1008 may secure each connection of bolts 1006 through connection plate 1002 and guardrail beam 1000. In a particular embodiment, the boltholes 1004 and boltholes in guardrail beam 1000 may have a diameter on the order of approximately ⅞ inch. In such an embodiment, threaded bolts 1006 may include 2½×¾″ GR. 5 bolts. However, it is recognized that these sizes are provided as examples only. Any appropriate size of boltholes and bolts may used to secure guardrail beam 1000 to connection plate 1002.
Connection plate 1002 is coupled to a threaded rod 1010. In a particular embodiment, threaded rod 1010 may be welded to connection plate 1002. As best shown in
The presence of nut 836 prevents withdrawal of cable 1010 from the openings formed by V-shaped cutout 814 of flange plate 810 and U-shaped cutout 826 of washer plate 824. Since the opening of keeper plate 816 includes an enclosed circular opening 818 rather than an open cutout in the edge of the keeper plate 816, keeper plate 816 ensures that threaded rod 1010 is properly in place. Keeper plate 816 also adds strength to the tensile connection of threaded rod 1010 to terminal post 800. Washer plate 824, which functions as a washer between bolt 834 and keeper plate 816, also adds strength to the connection.
During an end-on or redirective impact to a guardrail system incorporating the above-described features, the assembly described in
In contrast, when a vehicle impacts the guardrail system in a reverse direction, the tensile connection of guardrail beam 1010 may be released. For example, the reverse-direction impact may cause the upper edge 820 of keeper plate 816 directly above circular opening 818 to be sheared. Threaded rod 1010 is then freed from the openings formed by V-shaped cutout 812, U-shaped cutout 826, and circular opening 818. Because the tensile connection in guardrail beam 1000 is released, guardrail beam 1000 may be controllably collapsed to prevent vehicle instability or excessive deceleration.
To further aid in the release of the tensile connection during a reverse-direction impact, a modified strut may be used to couple the terminal support post to the first adjacent support post. Such a strut is indicated as reference numeral 140 in
As best shown in
When a vehicle impacts the guardrail system in a reverse direction, strut 1112 and strut plate 1114 may facilitate the release of the tensile connection between the guardrail beam and the terminal support post. Strut plate 1114 is positioned proximate the outlet end of flattening portion 112. Strut plate 1114 operates as a ramp to facilitate the lifting of the threaded rod coupled to the guardrail beam from the V-shaped cutout 814 of flange plate 810, circular opening 818 of keeper plate 816, and U-shaped cutout 826 of washer plate 824. Because the tensile connection in guardrail beam 1000 is released, strut 1112 and strut plate 1114 prevent instability or excessive deceleration of the impacting vehicle.
As described above,
Cable rods 1204 may traverse through a flattening portion 1206. Flattening portion 1206 may be similar to flattening portion 110 of
Technical advantages of particular embodiments of the present invention include a guardrail end treatment that dissipates impact energy through the compression of a W-beam guardrail element. Specifically, the guardrail end treatment may dissipate impact energy of a vehicle colliding with an end of a guardrail by flattening a portion of the guardrail required for deceleration of the impacting vehicle. Another advantage may be that the end treatment forces the W-beam guardrail element through a flattening structure that squeezes the guardrail into a relatively flat plate. In contrast to prior systems, the W-beam guardrail element may be flattened vertically rather than horizontally.
Still another advantage may be that a tensile and resistive coupling may be provided for connecting an end of the W-beam guardrail element to a terminal support post. The components of the system that provide the tensile connection of the guardrail beam to the terminal support post may enable the guardrail beam to remain secured after an end-on or re-directive impact. Thus, the system may remain in tension during both types of impacts. Still another advantage may be that the tension is released when the system is impacted in the reverse direction near the terminal end, however. The releasing of tension in the guardrail element for reverse direction impacts prevents vehicle instability and excessive deceleration Although the present invention has been described by several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the present appended claims. For example, the features described above may be used independently and/or in combination with each other or other design modifications.
