In need of a bridge

[doc_cottom]

word has it retired flat bed semi's work well for bridges. Designed to clear span
quite a few pounds

your likely to find them 28-40' ish. Which would mean building out the embankmanets a bit, but should be farily easy if you can figure out how to get the thing there ( i guess it would need to be set by a crane after you torched off the axles.

A flat bed semi-trailer specs are in the area 10,000Lb in any 10ft span, but do not exceed 50,000 pound total. That is some very basic numbers, aluminum trailers would be different. Don't forget, a flatbed semi-trailer is very flexable torsionly, lengthwise they well wind-up like a big spring if you load them heavily near the edges. Their stength is longitual above the main beams. Most flatbeds that are retired would be 40 to 45 ft. long. The 48 ft. is popular today. Also, the wood decking material used on most flatbed trailers will not standup to high per square inch loading. An example, you cannot drive a loaded forklift on the wood decking between the side rails and the main beams, the wheel loading will punch a hole right through.

 

[toolaholic]

A TRUCK flatbed is LIGHTWEIGHT compared to a rail road flat car. This bridge is near me, and I've been under it. IF ANY ONE WANT'S PIX ,I'll go back under.
They also did some kind of grey textured undercoating on the underside.

 

[Renze]

as said, the guy is only using it for foot load, no forklift wheel load.

the trailer frame will do just fine even if you drive your tractor over it, because both ends are supported on solid ground (not by springs of any kind) torsion of the trailer frame is no problem at all.

 

[gordon21]

Sandman2234: I am about 99% sure all our pup trailers and 53's have a frame. They are 3 compartment refrigerated trailers. The floors appear to be welded aluminum with the drainage channels. A dry box may not be built as strong and now that I think about it, many dry boxes have wood floors.

 

[sandman2234]

We have wood and aluminum floor drybox trailers. Floor material has very little to do with the strength of the sidewalls or frame.
They do make framed dryboxes, but they are usually used for a particular reason.
We also have refriderated trailers, and the floors in the newer ones are welded aluminum, because they last longer than most anything else that isn't too heavy to use. I only know of one refer trailer with a wood floor, and it was removed from service last year, but is still siting on our yard.
Wood floors actually are meant to drive forklifts on, but due to the wood decaying and becoming weak with time it doesn't take much to allow it to punch thru when a forklift drives on it. There is a new wood floor container trailer with a 24,000 pound forklift rating and it is says so on the back of the trailer.
I purchased a used flatbed years ago with an alunimum floor and last week dragged the center sections out of the woods to see about using them on my trailer I am working on right now.
The shorter trailers don't have the length to make the bridge laws required these days by the D.O.T., which is why they keep selling longer and longer trailers. Won't be long before the 48' ones are no longer in use.
David from jax

 

[em14]

"The shorter trailers don't have the length to make the bridge laws required these days by the D.O.T., which is why they keep selling longer and longer trailers."
Sandman,
Could you explain what this is about please? I wasn't aware of such. Thanks.
Leo

 

[Swisher]

What about a railroad container and cut the ends out.

 

[QRTRHRS]

Perhaps you could locate a stretch flatbed. These trailers have pretty stout interlocking frame rails with a pin release to adjust the length. Long for long loads and then back to normal length for more normal manuevering.

Set up the length you need, brace it upward to minimize the sag then weld it together.

Any reasonably priced trailer is going to need redecking. As far as getting it back in the woods, a track loader might be the ticket.

 

[dynasim]

I think a 50 ft suspension bridge, for foot traffic only, would be an interesting, fun thing to build. It wouldn't be to difficult, either, if the load rating was limited.

It would also make visitors like me envious!

The anchor points on the ends are the most difficult, and critical. The vertical posts can only provide vertical support. There is a large amount of tension on the cable. It would be worth going through(or having someone else go through) the calcs to ensure that you have enough of an anchor.

Chris

 

[sandman2234]

Em14,
Bridge laws are a little off topic for this discussion, but I thought I would toss a little into the discussion rather than ignore your question.

Bridge Formula Weights
The bridge formula was introduced in 1975 to reduce the risk of damage to highway bridges by requiring more axles, or a longer wheelbase, to compensate for increased vehicle weight. The formula may require a lower gross vehicle weight, depending on the number and spacing of the axles in the combination vehicle.

That was taken from this site
FHWA Freight Management and Operations - Freight Professional Development - Commercial Vehicle Size and Weight Program
in case you want to look at a more indepth explanation. Note the part about states being able to make laws for their own highways, as Florida has a very strange formula for calculations of their bridge laws. Using that formula, a truck can have up to approximately 44,000 pounds on a set of tandoms as long as they don't exceed the total bridge (max nears 71K) . Max weight is still at 80K, but it helps you when a shipper loads a load that would be over in most other states (standard 20K steer axle, 34K each tandom, 80K max). Don't try hauling a load legal in Florida into Ga because they don't see any humor in our laws.
David from jax