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Bridge Airbags

Giant airbags under bridges to mitigate disaster
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The recent bridge tragedy got me thinking: something must be done, and I have not yet heard anything proposed.

This is something.

All bridges would be retrofitted (in segments, of course) with giant airbags that deploy in case of collapse, to minimize damage and keep the segments floating.

For any given bridge, the expected failure mode of the bridge would be analyzed, and the proper number of airbag units would be placed under the bridge.

I expect that these devices would have different dynamics than a regular car airbag. The volume too be filled would be huge, and they would have to be sturdier. There may even be two airbags per module: one to absorb (at least some of the) impact, and the other to keep the segment floating. (For really tall bridges, these might even be tailored to slow the fall)

I envision a series of quick explosions forming a temporary inflated bridge which shields the fall of the actual one. The event might still be a disaster, albeit a smaller one.

There is, of course, the issue of what might be under the bridge during a fall.

[sorry, I haven't had the time to make this idea short]

cowtamer, Aug 03 2007

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       A bun for anything that might help. + My idea was to have a light before the bridge that only let a certain amount of cars enter onto the bridge at one time. I have always had paranoia being stopped on a bridge with a hundred other cars at the same time.
xandram, Aug 03 2007
  

       A more certain way to prevent disaster would be to spend some of the 1/2 trillion that has been poured into Iraq (and Halliburton, CACI, Blackwater, etc.) into restoring America's crumbling infrastructure.
nuclear hobo, Aug 03 2007
  

       The thought's in the right place, but the problem is getting the preventative work done in the first place (like with the levees in New Orleans). I don't understand why the leaders don't perform a simple cost-benefit analysis. Even assigning a finite value to human life I'm sure you can reach a computation where when the bridge collapses/disaster strikes/whatever (which will happen sometime), the number of lives lost + public anger/sadness/fear + additional cost to rebuild a city or bridge from scratch instead of just repair it, costs more than to improve its condition in the first place.
phundug, Aug 03 2007
  

       The cost benefit analysis has been done, and there is no benefit to repairing something. Once it fails catastrophically however, there are vast fortunes to be made in emergency funding of no-bid contracts to those who have properly funded political campaigns and stocked their boards with former government officials, CEOs and other well-connected interests.   

       If it were economically beneficial to fix the bridge, it would have been done long ago.
nuclear hobo, Aug 03 2007
  

       [hobo] has it exactly right. The way to prevent and reduce the impact of disasters is to maintain the infrastructure. What [cowtamer] is proposing is adding another, probably more fragile, system to the assemblage. An additional system to (not) maintain. An additional point of failure.   

       I predict when they analyze the data from the latest collapse they will find that the failure point is something that is noted in a recent maintanence report. Something that is listed as an item of interest in the 2005 inspection. Something that is marked up in the 1990 evaluation. And something that the original design team pointed out should be carefully tracked. In other words something that should have been avoidable.
Galbinus_Caeli, Aug 03 2007
  

       air balloons under a fallen mass in water serves only to tip its load sideways as the heaviest part of this balloon stacker tries to reach the lowest point.   

       agree with Galbinus about not adding an additional breakable system insteadof fixing the existing one. (although I'm sure you didn't mean it to be mutually exclusive, there is only limited funds when building anything, and fixing a problem from the start versus planning on having the problem later seems an easy choice.)
k_sra, Aug 03 2007
  

       As much as I hate to say it, [nuclear hobo] is right. I can't stand how our gov't works, or doesn't work!
xandram, Aug 03 2007
  

       Me either, [NH] expressed something that needs to be changed. The big contractors who fix these things make more money after a disaster than when they have to bid. They don't give a shit if people die.
nomocrow, Aug 03 2007
  

       Well identified problem, but the solution is in the wrong place. What we need are more advanced cars, capable of maintaining occupant survival under extreme bridge collapse conditions.   

       I imagine fitting explosives in every car. A motion sensor, similar to that used to trigger conventional airbags, detects that the car is on a collapsing bridge. Perhaps this could be verified through the use of GPS location, correlated to map positions of bridges.   

       As the car is about to impact at the bottom, the explosives are fired causing lift that exactly balances the current rate of descent.   

       The occupants of the car experience a soft landing. An on-board computer then radios for help (again that GPS system comes in handy) and advises by voice synthesis the occupants about the next steps for maximum chance of survival.
AllyAl, Aug 03 2007
  

       All of the above aside, the idea is good fodder for the 'bakery.   

       The bags should be so massive and so overpowered as to provide as much damage in the inflation cycle as the bridge incurred in the event that triggered the bags.   

       [AllyAl], that should be a whole new idea.
normzone, Aug 03 2007
  

       If the bags go out to the sides, and are big enough, the bridge segment wouldn't tip over to the side. Some helicopters have airbags on their skids that do something similar.   

       My concern is that the bags would be punctured by bridge pieces, car exhausts, trains and such. And they'd knock over a lot of people. [ ]
baconbrain, Aug 03 2007
  

       I imagine the bags (the ones you'd use for impact, at least) wouldn't have to last too long...their purpose would be to dampen the impact in case of a catastrophe and give some people a better chance to survive.   

       As for maintaining the infrastructure: I agree, that's the 'right' thing to do--just like not crashing your car is the right thing to do. Unfortunately, both modes of failure are possible.
cowtamer, Aug 03 2007
  

       Does anyone yet know what caused the bridge to collapse? Presumably it is faulty design, faulty construction. faulty maintenance or (unlikelily) freak conditions.   

       Unless it is the last of these, it will be cheaper and more effective to remedy the problem than to add airbags or other such features. Bridges are not meant to collapse, and we understand how to stop them from doing so.
MaxwellBuchanan, Aug 03 2007
  

       In the case of this Interstate bride, all of the truss-work was underneath, and that would have broken the fall of the roadway. In fact, the way it was constructed, there would have been no place for airbags.
ldischler, Aug 03 2007
  

       Or we could just stay home. (Don't most of us anyway?)
Ander, Aug 04 2007
  
      
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