Perimeter Security Barriers

This invention relates to perimeter security barriers, and in particular but not exclusively, to barriers that provide an effective perimeter protection against wilful intrusion around airports and the like.

Conventional perimeter security barriers are designed to withstand vehicle impacts but differ from road crash barriers in that they resist vehicle impacts in a direction substantially perpendicular to the perimeter barrier. Conventional road crash barriers, by contrast, are designed to deflect vehicles impacting the fence an angle of 15 to 25 degrees relative to the fence (i.e. low angles) at speeds up to 110 km/h (68 mph).

The problem with conventional perimeter security barriers is that they are unable to prevent transgression of heavy impacting vehicles. They are of solid construction, usually of concrete blocks, making them unsightly and difficult to install. It is therefore an aim of the present invention to provide a perimeter security barrier that can arrest heavy vehicle impacts (e.g. goods vehicles).

According to the present invention, there is provided a perimeter security barrier for restraining a vehicle impacting the barrier from a predetermined direction substantially perpendicular thereto or between 25 and 90 degrees relative to the barrier, the barrier comprising a pair of spaced apart end posts rigidly fixed in or on the ground, at least one intermediate post disposed between the end posts also fixed in the ground, and at least one wire rope between the end posts, wherein the rope is secured at each end to respective end posts, and energy absorption means is provided at said each end for absorbing energy transmitted by the ropes from the impacting vehicle. Embodiments of the present invention can therefore restrain vehicles impacting the barrier at high angles. Embodiments of the invention may be used as anti-terrorist fences and/or for restraining heavy vehicles.

In a preferred embodiment, the rope is secured to the end posts via the energy absorption means that may be configured to deform as the ropes tension under the action of the impacting vehicle. A section that deforms or collapses in the event of a

vehicle impact may provide the energy absorbing means. The section may be a steel channel section or a form of rubber or plastic sandwich compound.

Barriers embodying the present invention are advantageously configured so that the height of the barrier is effective for resisting vehicle impact along its entire length between the end posts.

Any or all of the at least one wire ropes may be located at a predetermined height above the ground. Means may be provided, configured for retaining the at least one rope at this predetermined height during an impact.

In an embodiment, the at least one wire rope may be attached to one or more of the at least one intermediate posts. The attachment of the rope(s) to the intermediate posts and/or the fixing of the at least one intermediate posts in or on the ground keeps the ropes substantially at the predetermined height during an impact.

In an embodiment, the ropes may be supported on the intermediate post(s) by hooks configured to permit release of the ropes relative to the intermediate post(s) in an upward direction. In the event of an impact, the release of the ropes from the posts assists in maintaining the ropes at the desired height above the ground.

In another embodiment, any or all of the at least one intermediate posts are releasably fixed in or on the ground. Any or all of the at least one intermediate posts may be frangible or mounted on a shear base mechanism. In the event of an impact, the post shears at its base. One or more of the ropes may remain attached thereto during an impact.

One or more additional wire ropes may be provided. A second rope may be provided and may be woven around at least one intermediate post with respect to the first rope. Further ropes may be added, unwoven or woven relative to the intermediate post. At least one of the ropes is positioned about the intermediate post such as to be disposed on a side thereof facing the predetermined direction. In a preferred embodiment, three additional wire ropes, unwoven relative to the intermediate post such as to be disposed on a side thereof facing the predetermined

direction, are provided. The barrier may have two pairs of wire ropes woven around said at least one intermediate post, one of which is positioned towards the top of the end and intermediate posts, and the other being positioned substantially midway between the top of the posts and the ground. One of the three additional wire ropes may be positioned between the pairs of wire ropes and the other two of said three additional wire ropes are positioned between the midway pair and the ground. The ropes are preferably tensioned between the end posts. The wire ropes may be of any suitable material, including steel strand or cable, or a high-carbon, high-tensile steel strand, or a fibre reinforced plastic material.

The intermediate posts are preferably inclined relative to the vertical towards the predetermined direction, that is, towards the oncoming vehicle. The inclination of the intermediate post(s) to the vertical may be between 0 and 45 degrees, preferably between 0 and 20 degrees, and more preferably 10 degrees.

Embodiments of the present invention are advantageous in that they may resist or prevent transgression of heavy goods vehicles impacting at speed in a direction substantially perpendicular to the perimeter or in a direction between 25 and 90 degrees to the perimeter. Embodiments may be designed to prevent access to secure areas, such as airfields or airports, by goods vehicles up to 7,500Kg inertial mass impacting the barrier at up to 90 degrees at speeds of to 48 to 80 km/hr. Embodiments may be able to withstand impact energies in the order of 1852 KJ.

The invention will be further described by way of example with reference to the accompanying drawings, in which: -

Figure Ia is a front elevational view of a perimeter security barrier embodying the present invention;

Figure Ib is an end view of the barrier of figure 1 showing the relative inclination of the intermediate posts relative to the end posts;

Figure Ic is a plan view of the barrier of figure 1;

Figure 2a is a detailed view of the end post taken in the direction of arrow A in figure Ia;

Figure 2b is a front elevational detailed view of the end post;

Figure 2c is shows an energy absorbing device for use in embodiments of the present invention;

Figure 3 a is a view in the direction of the arrow A of figure Ia of an intermediate post that may be adopted in embodiments of the present invention;

Figure 3b is a view of a post similar to the one of figure 3a at a different inclination angle;

Figure 4a is a detailed view of an intermediate post embodying the present invention;

Figure 4b is a support for wire ropes of the barrier; and

Figure 5 shows a base of a post for an embodiment of the present invention.

Figure 1 shows a barrier 1 having a pair of vertical end posts 3, 5 anchored into the ground by concrete blocks 7 and 9 respectively. The barrier has intermediate posts 11a, l ib, l ie that are also anchored into the ground by being bedded in concrete blocks 13a, 13b, 13c The barrier 1 is intended to restrain heavy vehicles impacting from a direction that is substantially perpendicular to the line of the barrier. The strength and design detail of the posts and concrete footings is such as to prevent breach of the barrier by a heavy goods vehicle in the order of 7500 kg inertial mass impacting the barrier at a speeds of about 64 - 80 km/hr.

Figure Ib is an end-view of the barrier from the direction of the arrow A from which it can be seen that the intermediate posts l la are inclined at an angle of 5 or

10 degrees relative to the vertical in a direction towards the anticipated impacting vehicle (travelling in the direction of arrow B).

The barrier 1 includes seven wire ropes 15a to 15g that span the line of the barrier between the end posts 3, 5. The ropes may be of high tensile steel and pre- tensioned between the posts 3 and 5. In this embodiment, they are arranged such that two pairs 15c, 15d and 15f, 15g respectively are sinuously wound around the intermediate posts 11 a.... as illustrated in the plan view of the barrier in figure 1 c. Figure Ic includes a detail drawing showing the ropes 15a, b, c, e and f being placed on the outer face of the intermediate post l la, the outer face being defined by the side of the post l la facing the incident vehicle that would be anticipated to approach the barrier 1 from the direction of the arrow B. Ropes 15d and 15g of the woven pairs

15c, d and 15 f, g respectively are placed on the opposite face of the intermediate post 1 Ia as shown. It follows that the ropes 15d and 15g will pass the next intermediate post 1 Ib on the outer face thereof, whereas the other ropes 15c and 15f of the respective pairs will be placed on the opposite face thereof. Placement of 5 of the 7 ropes on the outer face of the intermediate posts increases the maximum resistance to perimeter ingress of the impacting vehicle. The ropes may be disposed at a height of between 300 mm and 2 meters above the ground. Ropes may be provided at varying heights above the ground, for absorbing energy from a variety of vehicles of varying sizes. An impacting vehicle impacts the ropes which pushes back on the intermediate posts. This transmitting energy to the intermediate posts adjacent to the impact zone, thereby spreading the impact load, as well as to the end posts 3 and 5 as will be described in more detail below with reference to figure 2b. The inclination of the intermediate posts maximises the plastic work contribution of the posts in restraining the loadings imposed by the impacting vehicle.

Figure 2a shows the end view of the barrier 1 from the direction of the arrow A of figure Ia in more detail. Strengthening webs 17 are provided between the end post 3 and a base plate 10 that is in turn supported on the concrete footing 7. Figure 2b shows the relative height positioning of the wire ropes 15a to 15g. The height position of at least some of the ropes is selected to be such that the engine of the impacting vehicle impacts them. The wire ropes pass through the post 5 and are terminated and held in tension by terminal fittings that may be in the form of bolts or other suitable mechanical gripping devices 16a to 16g. A load or energy-absorbing device 21 is provided between respective ends of the ropes and the posts 3 and 5. This device 21 may be in the form of a hot rolled channel section or hollow tube 23 that is configured to absorb energy transmitted from the impacting vehicle by the ropes. The energy-absorption means 21 is designed to deform under the increased tension load in the ropes during impact by a vehicle. This limits the peak rope loads to tolerable levels and restrains the ropes in order that they develop tension to resist penetration or breach of the barrier by the impacting vehicle.

Figures 3a and 3b show the inclination of an intermediate post 1 l(a), in the former case, the angle of inclination is 5 degrees and in the latter case it is 10 degrees. Figure 4a is an enlarged view of the intermediate post of figure 3a or 3b and shows

hooks 17a to 17g for supporting the wire ropes 15a to 15g such that they may be displaced and separated on impact by a vehicle in an upward direction. Figure 4b is a detailed view of a hook 17a - 17g formed from a stainless steel bar 25. The design parameters of the barrier 1 are such that on impact, the intermediate posts 1 Ia.... are pushed back to incline away from the impact direction by up to 40 degrees. The placement of most of the ropes on the outer face of the intermediate posts provides for spreading of the impact load across more posts so that perhaps 5 or more of these posts will be pushed and inclined backwards on impact. The angle 27 of the hook 25 is such that the cables will tend to separate from the hook when the intermediate posts are pushed back during impact.

In an alternative embodiment, shown in Figure 5, the intermediate posts 11a... are releasably fixed to the ground. A mechanism may be provided at the base of the intermediate posts 11a..., that enables the post 11 a... to detach from a base 12 in the event of an impact. In the embodiment shown in Figure 5, the intermediate post 11a... may include a shear base 12 or a frangible support post. On impact, the base of the post 11a... releases from the foundation or base 12, e.g. via a shear mechanism such as a pin 14, or fracture of the material. The intermediate post 1 1a... in this embodiment would remain connected to one or more of the ropes 15a... and assist in maintaining the spacing of the ropes 15a... within the impacted zone to render the barrier better equipped to resist a second impact.

An electric current may be passed through one or more of the wire ropes of the barrier and coupled to detection equipment configured to permit detection of the location of an impact on the barrier. This may be used to trigger an alarm or warning device.