Assessing Primitive Bridge Strength

[Explorer 1]

Check out this bridge crossing......

When it comes to assessing a crossing, this bridge was labeled that it could handle 6 loaded ponies,
Enjoy,




Thanks,
Fred
Explorer 1

 

[Root Moose]

Not to be nit-picky but given some of you guys pass back and forth across the border it may be worth being clear about tons versus tonnes.

1 ton (i.e. U.S. short ton) is 2000 pounds

1 tonne (i.e. metric) is 1000 kg

1 kg is ~2.2 pounds so 1 tonne is ~2200 pounds.

So for the sake of quick assessment 1 ton equals 1 tonne.

http://en.wikipedia.org/wiki/Tonne
http://en.wikipedia.org/wiki/Ton

 

[I Leak Oil]

Unless you have 10 tonnes then it's really 11 tons.:sombrero:

 

[Root Moose]

And a dozen bakers dozens isn't 144 either. :elkgrin:

 

[michaelgroves]

Not to be nit-picky but given some of you guys pass back and forth across the border it may be worth being clear about tons versus tonnes.
...
So for the sake of quick assessment 1 ton equals 1 tonne.

Yes, for most purposes a ton is a tonne. What requires more consideration when doing assessments in different countries is the difference in safety factors when a bridge is rated in the first place. A bridge marked with a 10 tons limit in Europe or North America will almost certainly be good for at least double that, and probably many times more than that. In third-world countries it might not actually be good for 10 tons, even when new!

A few gratuitous pics of dodgy bridges in Zaire (1995), including a couple where the logs shifted apart, and a wheel dropped through, and one where we bypassed...

 

[UK4X4]

"you could have a samurai or tracker on 33"-12.5 (or pick any big tire) crossing before you.. that sure doesn't mean you will be able to.. "

yep.........but when your cross or not to cross is a 400 mile detour decision
or even a turn back in some instances.....

You may have very little information to go on........

Tires tracks simply mean some one else passed recently and it did'nt collapse for them


Love the overland Bedford truck pics...........I used to drive one of those in the UK army......great fun....

 

[off.track]

A bridge marked with a 10 tons limit in Europe or North America will almost certainly be good for at least double that, and probably many times more than that.

that may not be the case at all.. don't make that possibly deadly assumption. many bridges that are market 3t can barely handle that.. this pertains mainly to wild bridges, if you will.. paved ones in the cilivilzation, i think Michael is right.

 

[fisher205]

If you are overweight on a limited bridge and are caught using it, prepare to buy it. Bridges aren't cheap. Most weight limits aren't the failure limit but the weight the bridge can handle without some damage to it. Alot of bridges are limited by their decking, than the frames.

 

[charlieaarons]

I would like to add that despite the temptation to go fast over a relatively level but questionable bridge to minimize "risk time", going as slow as possible (under 5mph) minimizes the stress on the structure. This is true of ice as well, many ice roads over lakes and rivers have slow speed limits.

Charlie

 

[njtaco]

When it comes to assessing a crossing, this bridge was labeled that it could handle 6 loaded ponies,
Enjoy,

(snip)

Thanks,
Fred
Explorer 1

Thanks for the video...what does a loaded pony weigh? 800 lbs? 1000lbs? is that a metric loaded pony, or an American loaded pony?

 

[Christian]

Thanks for the video...what does a loaded pony weigh? 800 lbs? 1000lbs? is that a metric loaded pony, or an American loaded pony?

Scene from Monty Python and the Holy Grail:
Bridgekeeper: What... is the air-speed velocity of an unladen swallow?
Arthur: What do you mean? An African or European swallow?
Bridgekeeper: Huh? I-- I don't know that! Auuuuuuuugh!
Bedevere: How do know so much about swallows?
Arthur: Well, you have to know these things when you're a king, you know.

Sorry I could'nt help myself...

Here's a pic of a suspension bridge we crossed in Norway this summer. It has a 35 metric tonnes rating and we drove in the "wake" of a big truck. It was like being on a boat, it really rolled lengthwise, enought to give you that butterfly feeling in the stomach like when you drive over really sharp hills at speed:

 

[kerry]

http://www.youtube.com/watch?v=jFM-Z4P9Fb0&feature=related