Dragon's Teeth Development History
The Defence-Structures Dragon's Teeth Vehicle
Security Barrier (VSB) is a freestanding road defence barrier system.
Individual units (teeth) are linked at the front by a steel beam
section and at the rear by flat steel plates (previously chain) to
allow displacement during impact.
The Dragon's Teeth VSB was impact-tested in
accordance with the BSI PAS 68:2007 Impact test
specifications for vehicle security barriers in order to
evaluate its performance versus a vehicle borne penetrative attack.
Test 1: the road
barrier was set out as shown in Photo 1 with the frangible steel beam
linking the front and chain linking the rear. The vehicle used was a
7.5t (N2) 2-axle rigid with an impact speed of 47.1km/h at an angle of
90 degrees to the line of the impact face. The barrier stopped the
vehicle with negligible penetration and without losing its integrity.
This road barrier comprising of 6 Dragon's teeth achieved an impact
rating of: BSi PAS 68:2007/V/7500[N3]/48/90:0/0
The Dragon's Teeth Vehicle Security Barrier
performed as expected with the road defence system stopping the load
carrying platform of the HGV with zero penetration beyond the original
rear face of the system and with no dispersion of major debris. The
defence barrier was displaced in the direction of impact by 3m
suffering minor damage to the teeth and frangible steel sections. See
photos 2 & 3.
|Test 1: Barrier before impact
||Test 1: Overhead view after impact
||Test 1: Side view after impact
Test 2: the road
barrier was assembled using the same components as Test 1. The vehicle
used was a 7.5t (N3) 2-axle rigid with an impact speed of 80km/h. This
road barrier comprising of 6 Dragon's teeth achieved a BSI
PAS 68:2007 impact rating of V/7500/80/90 : 11.8/7.5.
The Dragons Teeth Vehicle Security barrier was
assembled as in Test 1 using the original teeth but replacing the steel
beam and chain links. The higher energy generated by the N3 class
vehicle compared to the N2 vehicle (Test 1) resulted in the connecting
chains breaking, causing the teeth to rotate and separate; allowing the
vehicle to penetrate through the road defence barrier. The vehicle
suffered significant damage and was immobilised. See photos
4, 5, 6. A re-design of the rear connection was required to
prevent separation of the teeth and improve impact performance.
|Test 2: View of Links after impact
||Test 2: Side view after impact
||Test 2: Front view after impact
Test 3: the setup was
a repeat of Test 2 using the same vehicle class and impact speed. The
rear links of the road barrier were re-designed to replace the chain
link with an arrangement of steel plates to form a flat chain. This
road barrier comprising of 6 Dragon's teeth achieved an impact rating
of: BSI PAS 68:2007/V/7500/80/90:7.9/0.
During impact the rear connections performed well,
absorbing the impact energy by deforming without breaking, thus holding
the road defence system together. This gave a greater impact resistance
by maintaining the overall mass of the road barrier. The impacting
vehicle suffered severe damage and was immobilised. See
photos 7, 8, 9.
|Test 2: Rear view after impact
||Test 2: From inside the barrier
||Test 3: From outside the barrier
Test 4: to enable
vehicle access through the Dragon’s Teeth VSB a 4.5m aperture swing
gate has also been developed. The gate, supported by 3 Dragon’s Teeth
either side, comprises a single boom and is manually operated with a
simple latching mechanism. The vehicle used was a 7.5t (N2) 2-axle
rigid with an impact speed of 80km/h, so that the gate could be
performance rated at a similar level to the original Dragon’s Teeth
VSB. This gate comprising of 6 Dragon's teeth (3 either side) achieved
an impact rating of: BSI PAS 68:2007/V/7500[N3]/80/90:6.2/10.3.
As before, previously impacted Dragon's Teeth
could be used to assemble and support the swing gate. The impact
resulted in the gate boom deforming significantly before unlatching.
The impact caused severe damage to and immobilised the vehicle. See
photos 10, 11, 12.
The Dragon's Teeth VSB has also been subjected to
blast testing to further evaluate its performance.
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