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Did you see the truck in the video take out an enormous steel beam that was presumably attached to the structure of the tunnel in some kind of permanent way? Ho

by evan_ 13y ago

Did you see the truck in the video take out an enormous steel beam that was presumably attached to the structure of the tunnel in some kind of permanent way? How would your solution avoid the same fate?

gojomo 13y ago
The warning beam is several stopping-distances before the tunnel itself, and far easier to replace/reconstruct. I'd try a 3-stage contact-warning system: (1) hanging bar that makes noise on contact but causes little damage. This might even go before a suitable turn-off. (2) breakaway cord with trailing noisemakers. This would be torn from its mast by the collision, and drag noisy items behind, emphasizing the need to stop and investigate. (3) hard bar providing some slowing/resistance (but almost certainly not full stopping power, given the position and expense). By design this would actually damage the vehicle (and even risk harming the driver), approaching the same level of damage that would occur at functional tunnel-entry. But, it'd happen earlier where easier to clear/repair.
- numbsafari 13y ago
  And yet, with this solution, no repair is needed for either the truck or the infrastructure. The vehicle is able to be removed under its own power, the driver is not injured, there is no debris. If you are in a vehicle behind a truck that has damage to its top, you very likely will have damage to your vehicle from flying debris.
  - joezydeco 13y ago
    Or a ten-ton beam falling on your car.
  - gojomo 13y ago
    Oh, I like the water-wall too. But a driver who misses the 1st two no-damage physical-contact warnings I've proposed -- and thus would hit the damaging third hard bar -- would quite possibly ignore the water-wall too. After all, the water wall seems primarily visual, and the driver has already missed numerous visual warnings. The contact protectors add collision-noise and vibration, which are rare enough that even a dozing/road-hypnotized driver is likely to take note. Comparative testing is of course justified.
gambiting 13y ago
Solid beam is probably a bad idea, but many tunnels have chains dangling above the road at the tunnel's maximum height - if you hit them, you will hear it,but they will do little damage to the vehicle.
- masklinn 13y ago
  Solid beam is an excellent idea as last recourse, from a structural POV since the vehicle is going to be destroyed anyway it's better to destroy it before it damages the tunnel itself.
twistedpair 13y ago
That beam they took out is called a "sacrificial beam." It was not a structural support, but was meant to take the impact before any structural members were damaged. You'll see them on many modern bridges and underpasses.
- wizzard 13y ago
  That's interesting and seems like a good idea, except perhaps it should be paramount that the 20-ton beam NOT fall on the following cars! That is an entirely different meaning of "sacrificial"...
  - twistedpair 13y ago
    See the videos on 11foot8.com, that beam is a freestanding structure separate from the bridge solely designed to decapitate trucks.
- JshWright 13y ago
  The sacrificial beam that appeared to fall on top of the car behind the truck?
Freestyler_3 13y ago
Something that causes the vehicles engine to stop... a shock? It wouldn't stop the vehicle but it will decrease destructive force. Or a trapdoor (warning this is a joke disregard it if you know you don't like jokes)
- bigiain 13y ago
  (intentionally ignoring joke warning…) Excellent plan! A trapdoor! In the harbour tunnel! Relevant anecdote: My Dad worked for the company who built the fire control system in the Sydney Harbour Tunnel. It's got (from fuzzy memory - numbers not guaranteed accurate) 128 sectors of "deluge valves". It's got pumps capable of keeping up with only 10 of those sectors of deluge valves - more than 10 sectors of valves open means even with all pumps running at maximum capacity the tunnel will fill up with water. There's some software controlling it all which is intended to ensure the operators don't accidentally flood the tunnel. Dad knows who wrote that software - he won't drive through the tunnel.
  - Freestyler_3 13y ago
    Yes, I hope though that the pressure on the writer of that software was enough to make him check thoroughly for errors.

by evan_ 13y ago

gojomo 13y ago

The warning beam is several stopping-distances before the tunnel itself, and far easier to replace/reconstruct. I'd try a 3-stage contact-warning system: (1) hanging bar that makes noise on contact but causes little damage. This might even go before a suitable turn-off. (2) breakaway cord with trailing noisemakers. This would be torn from its mast by the collision, and drag noisy items behind, emphasizing the need to stop and investigate. (3) hard bar providing some slowing/resistance (but almost certainly not full stopping power, given the position and expense). By design this would actually damage the vehicle (and even risk harming the driver), approaching the same level of damage that would occur at functional tunnel-entry. But, it'd happen earlier where easier to clear/repair.

numbsafari 13y ago
And yet, with this solution, no repair is needed for either the truck or the infrastructure. The vehicle is able to be removed under its own power, the driver is not injured, there is no debris. If you are in a vehicle behind a truck that has damage to its top, you very likely will have damage to your vehicle from flying debris.
- joezydeco 13y ago
  Or a ten-ton beam falling on your car.
- gojomo 13y ago
  Oh, I like the water-wall too. But a driver who misses the 1st two no-damage physical-contact warnings I've proposed -- and thus would hit the damaging third hard bar -- would quite possibly ignore the water-wall too. After all, the water wall seems primarily visual, and the driver has already missed numerous visual warnings. The contact protectors add collision-noise and vibration, which are rare enough that even a dozing/road-hypnotized driver is likely to take note. Comparative testing is of course justified.

gambiting 13y ago

Solid beam is probably a bad idea, but many tunnels have chains dangling above the road at the tunnel's maximum height - if you hit them, you will hear it,but they will do little damage to the vehicle.

masklinn 13y ago
Solid beam is an excellent idea as last recourse, from a structural POV since the vehicle is going to be destroyed anyway it's better to destroy it before it damages the tunnel itself.

twistedpair 13y ago

That beam they took out is called a "sacrificial beam." It was not a structural support, but was meant to take the impact before any structural members were damaged. You'll see them on many modern bridges and underpasses.

wizzard 13y ago
That's interesting and seems like a good idea, except perhaps it should be paramount that the 20-ton beam NOT fall on the following cars! That is an entirely different meaning of "sacrificial"...
- twistedpair 13y ago
  See the videos on 11foot8.com, that beam is a freestanding structure separate from the bridge solely designed to decapitate trucks.
JshWright 13y ago
The sacrificial beam that appeared to fall on top of the car behind the truck?

Freestyler_3 13y ago

Something that causes the vehicles engine to stop... a shock? It wouldn't stop the vehicle but it will decrease destructive force. Or a trapdoor (warning this is a joke disregard it if you know you don't like jokes)

bigiain 13y ago
(intentionally ignoring joke warning…) Excellent plan! A trapdoor! In the harbour tunnel! Relevant anecdote: My Dad worked for the company who built the fire control system in the Sydney Harbour Tunnel. It's got (from fuzzy memory - numbers not guaranteed accurate) 128 sectors of "deluge valves". It's got pumps capable of keeping up with only 10 of those sectors of deluge valves - more than 10 sectors of valves open means even with all pumps running at maximum capacity the tunnel will fill up with water. There's some software controlling it all which is intended to ensure the operators don't accidentally flood the tunnel. Dad knows who wrote that software - he won't drive through the tunnel.
- Freestyler_3 13y ago
  Yes, I hope though that the pressure on the writer of that software was enough to make him check thoroughly for errors.