I’m buying property that has a bridge made of an old 18 wheeler flatbed. The trailer is 35’ but only crosses about a 6’ wide creek bank. The rest of the trailer is buried. Anyone have any knowledge of what the bridge can hold weight wise? The trailer seems to be in decent shape and no signs of rot in the metal. I’m going to replace all the lumber with either 2x6 treated, 4x6 treated, or any suggestion from you guys. Railroad ties are an option as well. What say ye pack?
OT: Bridge made from flatbed
- Thread starter Dawg1979
- Start date
If you put 4x6 runners on, it should hold up trucks and small tractor easy. Probably anything under 80,000 lbs easy.
I’ve used a free software program called “beamboy” to do calculations for weight-bearing capacities of standard steel beams. If that’s what the longitudinal beams in the trailer are made from, you can figure it out yourself.
The program can be downloaded here:
https://www.softpedia.com/get/Science-CAD/BeamBoy.shtml
The program can be downloaded here:
https://www.softpedia.com/get/Science-CAD/BeamBoy.shtml
Generally speaking a flat bed can haul around 40,000 - 50,000 lb dynamically. From an engineering standpoint I would stick with that without doing an analysis. Keep in mind the weight of whatever timbers you add will need to be deducted from that the capacity. I would also inspect the cross bracing on the frame. The beams of a trailer are fairly tall and this bracing keeps the beams from bowing out when loaded.
If you are to use any type of solver you need to determine what the material was used for the beams. The material could range from high strength steel, mild steel or even aluminum. This variation in material can drastically affect the beam's capacity.
Looking at it for the first time, it looks like high strength steel. Until i get down there and really inspect it, i don’t know 100%. I deal with trucks daily, so i know weight capacities of the trailers, just want too sure if that would be the same maximum weight when someone is driving across it. Or if say a concrete truck would make it across.
Only problem w/ that is you will be constantly cleaning out from under it, a big limb or old dead tree floats down and gets stuck between power pole and the bank, then leaves and more limbs and then it becomes a beaver damn. Seen it happen a bunch
Bending may not be the limiting factor for the support beams shear limit must be taken into account also.
I'm not versed in what steel is used in normal flatbeds but high strength steel looks just the same as mild steel. I know in heavy haul trailers they use T1 (A514) a 100 ksi material but not sure about standard trailers.
If you are looking at a concrete truck you need to also consider the width of the vehicle. A concrete truck is 8' wide and you would be limited by the decking extending past the support beams. If I remember correctly the load from the two rear axles of a concrete truck are about 60 kips.
There's a company that builds bridges from old railcars that is local owned (Mississippi) I believe. Maybe they built yours as well. Anyway maybe you could call them and they would have an answer for you.
https://ibridgeco.com/
https://ibridgeco.com/
The property is south of Marshall, Tx. But i might call them and just see what they have to say and any insights. Thanks!!
That’s a really narrow gap for a trailer of that magnitude. What is the depth below bridge?
We have the same setup at deer camp, approx 30 feet across, and routinely take an 80 hp kubota with bucket and cab across with implements with zero notable bending. I’ll admit to being very sketched the first time I saw it.
We have the same setup at deer camp, approx 30 feet across, and routinely take an 80 hp kubota with bucket and cab across with implements with zero notable bending. I’ll admit to being very sketched the first time I saw it.
I used to have to cross this bridge. It wasn’t so bad on a tractor but crossing with a combine was a little sketchy.
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