GB2492078A

GB2492078A - Highway barrier

Info

Publication number: GB2492078A
Application number: GB201110322A
Authority: GB
Inventors: David Moseley
Original assignee: SAFER HIGHWAYS Ltd
Current assignee: HIGHWAY SAFETY PRODUCTS LIMITED
Priority date: 2011-06-20
Filing date: 2011-06-20
Publication date: 2012-12-26
Also published as: WO2012175956A1; GB201110322D0

Abstract

The barrier comprises a number of posts 204 attached to the ground with an elongate barrier section 212 attached to each post with an attachment formation. The attachment formation is designed to permit separation of the elongate barrier in a first direction, preferably towards the ground in use, if a specific force is applied. The attachment formation also either inhibits separation in a second, opposite, direction, or allows separation in the opposite direction if a force is applied which is larger than the specific force. The barrier may also include a number of flexible posts which may be more stiff in a direction parallel to the elongate barrier than parallel to it. The posts may also have varying degrees of stiffness wherein posts closer to the ends are more stiff than those in the centre.

Description

Highway barrier The present invention is concerned with a highway barrier. More particularly, the present invention is concerned with an end region for a highway crash barrier suitable for arresting and/or restraining vehicle movement.

Highway crash barriers are well known. Generally speaking, such barriers comprise a series of posts attached to or embedded into the ground. The posts are equally spaced.

A barrier section, commonly in a "W" shaped cross-section is attached to each post.

The bather extends alongside the road in question.

Such bathers are primarily designed to restrain obliquely-colliding vehicles. In addition, at the start and end of a barrier-protected zone, both oblique and "end on" collisions should be considered. This region of the barrier system is known as the "end terminal". The end terminal should be able to dissipate the energy of an end-on collision, bringing the impacting vehicle safely to rest without deflecting it back into the highway and potentially into flow of traffic. During oblique impacts, the vehicle should be safely brought to a halt, again so as to avoid re-entry into the flow of traffic.

End terminals need to expend as much energy as possible in order to absorb the kinetic energy of the impacting vehicle as it progresses along the bather. Known solutions use complex energy dispersion mechanisms in order to achieve this. For example, a series of overlapping barrier sections may be provided which are fastened together by bolts held in narrow slots. The bolts tear through the material betweeb the slots in order to dissipate energy.

An alternative design involves the provision of a forming head at the terminal which is progressively pushed along the barrier by the vehicle. This forming head deforms the barrier (for example by deflecting and reshaping the bather section) in order to dissipate the energy of the vehicle.

In the above example, energy is dissipated via the interaction between the end terminal and the bather section. Each of the posts is arranged to collapse under impact. All of the energy is dissipated by the interaction of the end terminal with the barrier section. The posts simply hold the barrier section up and are not designed to absorb significant energy themselves.

These systems are complex, expensive and often unreliable under unexpected load conditions. Each of the aforementioned barriers is tested under a specific set of test conditions. Such devices tend to be designed for test and may not perform as well under real life conditions, i.e., those different to test circumstances.

What is required is an inexpensive and predictable method of dispersing energy in an end-on vehicle collision with a barrier whilst retaining the ability to constrain the vehicle in a side-on or oblique impact.

According to a first aspect of the present invention there is provided a highway barrier comprising a plurality of posts attached to the ground and spaced apart in a first direction, an elongate barrier section attached to each post via an attachment formation, which barrier is spaced from the ground, in which the attachment formation is configured to permit separation of the barrier and post in a first direction at a first force level, and, either i) inhibit separation of the barrier and post in a second, opposite direction, or ii) permit separation of the barrier and post in the second, opposite direction at a second force level being higher than the first force level.

Preferably, the first direction is towards the ground in use and the second direction is away from the ground in use.

Advantageously, the present invention utilises the post to dissipate the impacting energy. In particular, once the vehicle impacts the end terminal, because the barriers and posts can separate in a first direction, the barrier will be pushed under the vehicle and the posts will be progressively deformed as the vehicle progresses.

In a second situation where the vehicle is impacting at an oblique angle (i.e. at any other situation than end-on), then the posts will typically be deformed away from the vehicle at a region of ground level. Because the barrier section is attached to a plurality of posts the load of a side impact is spread. Because of the nature of the attachment formation of to the present invention, the barrier section will not tend to detach in the second direction thus restraining the car and preventing it from leaving the highway.

Preferably, each post comprises a unitary element both connected to the attachment formation and partially embedded in the ground in use. Advantageously, this encourages bending of the post in order to dissipate the energy rather than any kind of two piece post with a frangible attachment which would break upon impact.

According to a second aspect of the invention there is provided a highway barrier comprising a plurality of posts and a barrier section attached to each post, wherein each post comprises a unitary element partially embedded in a ground surface and attached to the barrier section at a position spaced from the ground surface.

Advantageously, and in contrast to prior art devices, the posts have a unitary element which is embedded in the ground. As discussed, prior art devices use posts having a frangible element, whereas the present invention relies upon bending of the posts to absorb energy, Preferably, each post of the first or second aspect has a higher flexural stiffness in a direction perpendicular to the barrier section than parallel thereto. Advantageously, this encourages bending of the posts during an end-on collision to absorb energy but resists bending during a side-on or oblique collision and therefore helps to restrain the vehicle and prevent it riding over the barrier section in oblique collisions.

Preferably, the difference in flexural stiffhess is at least at a position near the ground.

Preferably, each post of the first or second aspect has a first cross-sectional moment of inertia about a first axis parallel to the barrier section which is higher than a second cross-sectional moment of inertia about a second axis perpendicular to the barrier section. This achieves the aforementioned function of a higher flexural stifihess under oblique impacts.

The posts of the present invention may become progressively stiffer the further along the barrier that the vehicle progresses. For example, a first post nearer the end of the barrier may have a lower stiffness than a post further along. As such, smaller vehicles wfth less energy would come to a controlled stop in the first section.

Larger vehicles with higher kinetic energy levels would not be stopped by the first section but would be arrested by the second, stiffer section. It will be noted that to simply provide a stiffer section at the beginning of the end terminal would arrest smaller vehicles too quickly causing injury to the passengers.

According to the invention, the posts may become progressively stiffer the further they are from the end or, as an altemative, there may be a plurality of zones in which the stiffness increases further from the end.

The posts may contain an energy absorbent filler material which may be used to tailor their stiffness and absorb the vehicle's kinetic energy. Filler material may extend from the top of the posts to an above ground position, preferably proximate the ground such that bending is encouraged at that location.

The filler material may be a foam or honeycomb structure.

Ahernatively, or in addition, at least one of the posts may comprise a stress raiser proximate the ground level. This stress raiser will encourage bending at a specific posftion and, as such, deformation can be controlled. The stress raiser may be a reduction in thickness in the wall of the post, for example a recess or notch.

Preferably, the barrier section is formed to be close to the ground at the first end of the terminal. This is advantageous as permits the vehicle to ride onto the end of the barrier section and deform the section downwards under its own mass. The vehicle captures the barrier section underneath it (and between the wheels) and the barrier is progressively pushed down towards the ground (as the attachments to the posts progressively fail).

The barrier section thereby forms a stabilising "rail" for the vehicle to travel along as its kinetic energy is dissipated. Energy is dissipated by each post being successfully deformed to absorb the kinetic energy of the vehicle. As the barrier section falls to the S ground it forms a natural rail to restrain the vehicle laterally and prevent it from riding off the barrier. As such, the present invention offers a controlled method of slowing the vehicle after an end-on collision.

A highway barrier according to the present invention will now be described with reference to the accompanying figures in which:-

FIGURE la is a side view of a prior art barrier;

FIGURE lb is a section view of the prior art barrier of Figure la along the line B-B; FIGURE 2a is a side view of a barrier in accordance with the present invention; FIGURE 2b is a section view of the barrier of Figure 2a along the line B-B; FIGURE 3a is a side view of the barrier of Figure 2a in a first deformed state; FIGURE 3b is a section view of the bather of Figure 2a in the first deformed state and along the line B-B of Figure 3a; FIGURE 3c is a section view of the bather of Figure 2a in a second deformed state; FIGURE 4 is a section view of a first post used in a bather in accordance with the present invention; FIGURE 5 is a section view of a second post used in a barrier in accordance with the present invention; FIGURE 6 is a section view of a third post used in a barrier in accordance with the present invention; FIGURE 7a is a section view of a fourth post used in a barrier in accordance with the S present invention; FIGURE 7b is a close up view of a part if the post of Figure 7a; FIGURE 8a is a section view of a fifth post used in a barrier in accordance with the present invention; FIGURE 8b is a section view of a part if the post of Figure 8a along line B-B; FIGURE 9a is a a side view of a further barrier in accordance with the present invention; and, FIGURE 9b is a section view of the barrier of Figure 9a along the line B-B.

Turning to Figures la and ib, a prior art highway barrier 100 is shown embedded into ground 10. The highway barrier 100 comprises a series of posts 102, 104, 106. Each of the posts 102, 104, 106 comprises an embedded ground part 108 and a mounting part 110 frangibly attached to the ground part by fasteners 112. A "W" cross-section barrier section 114 extends between the posts 102, 104, 106, and is attached to each mounting part 110 by bolts 116.

An end terminal 118 is provided at the end of the barrier section 114. The end terminal 118 is specifically designed to be pushed along the barrier section 114 upon an end on impact in direction D. The impacting vehicle continuously extrudes the terminal 118 through an orifice so that the kinetic energy of the vehicle is dissipated.

As the end terminal 118 progresses, each of the posts 102, 104, 108 detaches such that the attachment parts 110 separate from the ground parts 108 by shearing or failing attachments 112. Bohs 116 also fail as the barrier section 114 is extruded.

Turning to Figure 2a, a highway barrier 200 in accordance with the present invention is shown. Highway barrier 200 comprises a series of posts 202, 204, 206, 208, 210.

Each of the posts 202, 204, 206, 208, 210 is embedded in ground 20 as shown.

A "W" cross-section barrier section 212 is provided and is attached to each of the posts 202, 204, 206, 208, 210 by an attachment formation labelled generally at 214.

The barrier section 212 extends parallel to the ground and raised therefrom but gradually approaches the ground by ramping down towards an end 216.

Referring to Figure 2b, the attachment 214 comprises a first u-shaped attachment bracket 218 which has its open end facing away from the ground and is bolted to the barrier section 212. The attachment 212 further comprises a second u-shaped bracket 220 with its open end facing downwards, i.e. in the opposite direction to the u-shaped component 218. The second bracket 220 is bolted to the post 204.

The u-shaped brackets 218, 220 are engaged to overlap. Their mating faces are connected together by a frangible shear bolt 222 which is configured to fail at a pre-determined force.

Turning to Figure 3a, a vehicle (not shown) impacts the barrier 200 in the direction D. The lower end 216 of the section 212 is caught under the from of the vehicle and pushed downwards as the vehicle has progresses along the barrier 200. The vehicle impacts posts 202, 204 and deforms them such that they bed proximate the ground 20.

As the section 212 is pushed down, the u-section components 218, 222 separate as shown in Figure 3b shearing the frangible boh 222. This allows the barrier section 212 to move downwardly in direction A as shown in Figure 3b.

As it drops to the ground 20, the barrier section 212 forms a rail for the vehicle to travel on and is trapped between the vehicle wheels such that the vehicle continues in direction D, deforming each of the posts 202, 204. It will be noted that each post 202, 204, 206, 208, 210 has an above-ground height H which is at least equal to the distance P between successive posts. This means that the posts 202 etc also form a rail like structure when deformed which keeps the vehicle from veering laterally.

The alternative to an end-on collision is shown in Figure 3c. The barrier 200 has S undergone a side-on or oblique collision where the vehicle does not contact the end of the barrier 200, but rather impacts from the side. The post 206 is deformed upon impact and the vehicle pushes the barrier section 212 in direction C attempting to push it upward relative to the post 206. Under these circumstances, it is undesirable for the section 212 to become detached from the post 206 because restraint of the vehicle on the highway is the objective.

Under this load case, the two u-shaped components 218, 220 abut against each other and do not allow further progression of the section 212 up the post 206. The load path through the shear boh 222 is effectively shorted circuited (the load travels through the abutment of the parts 218, 220) such that the barrier section 212 restrains the vehicle.

As can be determined from the above discussion, and with reference to the embodiments as shown in Figures 2a to 3c, it is important that the barriers deform to absorb energy, particularly in the case of end-on impact.

Turning to Figure 4, a hollow post 300 is shown in section embedded in ground level 30. This post 300 can absorb energy by plastically deforming.

Turning to Figure 5, a post 400 has been filled with an energy absorbent filler material 402 such as a foam or honeycomb material which will absorb some of the energy of impact.

Turning to Figure 6, a post 500 has been partially filled with energy absorbent filler material 502 down to a level L proximate the ground 50. As such, when a vehicle impacts the post, it will be encouraged to bend at the weakest point, that is at ground level. This helps control failure of the post and form the aforementioned "rail".

Turning to Figure 7a, a post 600 is similar to the post 300 of Figure 4 but defines a notch 602 in its side wall proximate ground 60 which helps to encourage plastic deformation of the post 600 near ground level.

Turning to Figure 8a, a post 700 has an asymmetric cross-section as shown in Figure 8b. It will be noted that the post 700 has a higher flexural stiffness (i.e. a higher second moment of area) about an axis Q parallel with direction D (i.e. an axis parallel with the barrier section) and a lower flexural stiffness about an axis R perpendicular to the barrier section. This encourages bending in the direction D to absorb energy in the case of end-on impacts, but inhibits significant bending in the direction perpendicular to D in order to restrain the vehicle during oblique impacts.

Turning to Figures 9a and 9b, a further highway barrier 800 in accordance with the present invention is shown. Highway barrier 800 comprises a series of posts 802, 804, 806, 808, 810. Each of the posts 802, 804, 806, 808, 810 is embedded in ground 20 as shown.

A "W" cross-section barrier section 812 is provided and is attached to each of the posts 802, 804, 806, 808, 810 by an attachment formation labelled generally at 814.

The barrier section 812 extends parallel to the ground and raised therefrom but gradually approaches the ground by ramping down towards an end 816.

Referring to Figure 2b, the attachment 814 comprises a first u-shaped attachment bracket 818 which has its open end facing away from the ground and is bolted to the barrier section 812. The attachment 814 further comprises a second u-shaped bracket 820 with its open end facing downwards, i.e. in the opposite direction to the u-shaped component 818. The second bracket 820 is bohed to the post 804.

The u-shaped brackets 818, 820 are engaged to overlap. Their mating faces are connected together by a frangible shear bolt 822 which is configured to fail at a pre-determined force.

A horizontal rubbing strip 850 is provided which extends parallel to the ground 20 and to the barrier section 812. The rubbing strip 850 is located between the barrier section 812 and the ground 20, closer to the latter (although offset therefrom). The rubbing strip 850 is rectangular in cross section and is attached to each of the posts 802, 804, 806, 808, 810.

The intention of the rubbing strip is to provide additional stability to the vehicle in oblique impacts. In particular, it retains the wheels of the vehicle on the highway side of the barrier 800, and prevents them from passing underneath the barrier section 812 and catching on the posts 802, 804, 806, 808, 810 as the vehicle moves forward. The rubbing strip 850 is generally not as strong as the section 812 and has the primary function of stabilising the vehicle wheels during impact.

Claims

Ctaims 1. A highway barrier comprising: a plurality of posts attached to the ground and spaced apart in a first direction, an elongate barrier section attached to each post via an attachment formation, which barrier is spaced from the ground, in which the attachment formation is configured to permit separation of the barrier and post in a first direction at a first force level, and, either i) inhibit separation of the barrier and post in a second, opposite direction, or; ii) permit separation of the barrier and post in the second, opposite direction at a second force level being higher than the first force level.
2. A highway barrier according to claim 1 in which the first direction is towards the ground in use, and in which the second direction is away from the ground in use.
3. A highway barrier according to claim 1 or 2 in which each post comprises a unitary element both connected to the attachment formation and partially embedded in the ground in use.
4. A highway barrier comprising a plurality of posts and a barrier section attached to each post, wherein each post comprises a unitary element partially embedded in a ground surface and attached to the barrier section at a position spaced from the ground surface.
5. A highway barrier according to any preceding claim in which each post has a higher flexural stiffness in a direction perpendicular to the barrier section than in a direction parallel to the barrier section at a location above the ground.
6. A highway barrier according to claim 5 in which each post has a higher flexural stiffness in a direction perpendicular to the barrier section than in a direction parallel to the barrier section at a location nearer to the ground than the barrier section.
7. A highway barrier according to claim 5 or 6 in which each post has a first cross sectional second moment of inertia about a first axis parallel to the barrier section which is higher than a second cross sectional second moment of inertia about a second axis perpendicular to the barrier section.S
8. A highway barrier according to any preceding claim comprising a first end where the barrier terminates, in which a first post has a first flexural stiffness in the direction of the barrier section and a second post has a second flexural stiffness in the direction of the barrier section, and, in which the first stiffhess is lower than the second stiffness and in which the first post is further from the first end than the second post.
9. A highway barrier according to claim 8 comprising a first end where the barrier terminates, in which a first plurality of posts each has a first flexural stiffness in the direction of the barrier section and a second plurality of posts has a second flexural stiffness in the direction of the barrier section, and, in which the first stiffhess is lower than the second stiffness and in which the first plurality of posts is further from the first end than the second plurality of posts.
10. A highway barrier according to claim 8 in which each post becomes increasingly stiff in the direction of the barrier section moving away from the first end.
11. A highway barrier according to any preceding claim in which at least one of the plurality of posts contains an energy absorbent filler material.
12. A highway barrier according to claim 11 in which the filler material extends from the top of the post to an above-ground position within the post.
13. A highway barrier according to claim 11 or 12 in which the energy absorbent filler material is a foam or a honeycomb.
14. A highway barrier according to any preceding claim in which at least one of the plurality of posts comprises a stress raiser at or proximate ground level.
15. A highway barrier according to claim 14 in which the stress raiser comprises a reduction in thickness in a wall ofthe post.
16. A highway barrier according to any preceding claim comprising a first end where the barrier terminates, wherein the barrier section is formed to be closer to the ground at the first end.
17. A highway barrier according to claim 16 in which the barrier section ramps down towards the ground at the first end.
18. A highway barrier according to any preceding claim in which each of the posts has an above-ground height and a separation distance to the next post, in which the above ground height is equal to or grater than the separation distance.
19. A highway barrier as hereinbefore described with reference to, or in accordance with figure 2a onwards.Amendments to the claims have been filed as follows Ctaims 1. A highway barrier comprising: a plurality of posts attached to the ground and spaced apart in an along-highway direction, an elongate barrier section attached to each post via an attachment formation, which barrier is spaced from the ground, in which the attachment formation is configured to permit separation of the barrier and post in a first direction along the post at a first force level, and, either i) inhibit separation of the barrier and post in a second, opposite direction along the post, or; ii) permit separation of the barrier and post in the second, opposite direction along the post at a second force level being higher than the first force level, in which the first direction is towards the ground in use, and in which the second direction is away from the ground in use.2. A highway barrier according to claim 1 in which each post comprises a unitary It) element both connected to the attachment formation and partially embedded in the (4 ground in use.3. A highway barrier according to claim 1 or 2 in which each post has a higher flexural stiffness in a direction perpendicular to the barrier section than in a direction parallel to the barrier section at a location above the ground.4. A highway barrier according to claim 3 in which each post has a higher flexural stifthess in a direction perpendicular to the barrier section than in a direction parallel to the barrier section at a location nearer to the ground than the barrier section.5. A highway barrier according to claim 3 or 4 in which each post has a first cross sectional second moment of inertia about a first axis parallel to the barrier section which is higher than a second cross sectional second moment of inertia about a second axis perpendicular to the barrier section.6. A highway barrier according to any preceding claim comprising a first end where the barrier terminates, in which a first post has a first flexural stiffhess in the direction of the barrier section and a second post has a second flexural stiffness in the direction of the barrier section, and, in which the first stifihess is lower than the second stiffness and in which the first post is further from the first end than the second post.7. A highway barrier according to claim 6 in which a first plurality of posts each has a first flexural stiffness in the direction of the barrier section and a second plurality of posts has a second flexural stiffness in the direction of the barrier section, and, in which the first stiffhess is lower than the second stiffness and in which the first plurality of posts is further from the first end than the second plurality of posts.v 8. A highway barrier according to claim 6 in which each post is stiffer than the previous post in the direction of the barrier section moving away from the first end. (49. A highway barrier according to any preceding claim in which at least one of the plurality of posts contains an energy absorbent filler material.10. A highway barrier according to claim 9 in which the filler material extends from the top of the post to an above-ground position within the post.11. A highway barrier according to claim 9 or 10 in which the energy absorbent filler material is a foam or a honeycomb.12. A highway barrier according to any preceding claim in which at least one of the plurality of posts comprises a stress raiser at or proximate ground level.13. A highway barrier according to claim 12 in which the stress raiser comprises a reduction in thickness in a wall of the post.14. A highway barrier according to any preceding claim comprising a first end where the barrier terminates, wherein the barrier section is formed to be closer to the ground at the first end.15. A highway barrier according to claim 14 in which the barrier section ramps down towards the ground at the first end.16. A highway barrier according to any preceding claim in which each of the posts has an above-ground height and a separation distance to the next post, in which the above ground height is equal to or grater than the separation distance.17. A highway barrier as hereinbefore described with reference to, or in accordance with figure 2a onwards.LU (4