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May 25, 2013



Unfortunately, the armoured arch won't stop an assault with a hydraulic lift truck. Any lift-to-dump type truck or trailer, or mobile crane, could be activated while in transit. I've seen video of that hitting overpasses, and the dump types can be loaded with great weight to enhance the energy transfer.

Offhand, I suspect the only physical design for safety would be heavy plates lining the overhead to remove the rib access. Probably have to extend it all the way down to the road surface to avoid an angled hit. Lot of weight. Essentially, you end up with a steel tunnel. Bridge engineers would have a fit. Probably a major loss of weight rating for traffic.

Perhaps a steel net that would dissipate the energy without transferring it to the structure, something along the lines of a carrier arresting cable with a VERY short movement capability. Have to be anchored to the ground before the bridge.

Cheapest fix may be to limit the speed capability of any large vehicle that crosses a bridge. This would have to be a physical limit, like coming to a complete stop before the bridge. Then, having a barrier raised/lowered, and maybe obstacles that the vehicle would have to maneuver around while crossing, if it is long enough. the idea is to limit the distance that a truck could use to accelerate in. Keep these short. Essentially, you want chicanes that force a truck to move at very reduced speeds, somewhat like the approach to a checkpoint.

Truckers, and commuters, are going to scream about it, because it WILL impact the flow of traffic.

At this point, most overhead truss type bridges should probably cease to be built, due to this vulnerability.



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