Wooden bridge for 2000# tractor to cross creek

[LD1]

Wood is tricky. With a GOOD beam.....6x12....1000# of weight right in the middle you are only gonna deflect 1/4". So I'd say the 6x12 beams are within the capacity to carry a 2000# tractor.

But the problem with trying to calculate the load capacity is wood has too many variables. What species it is, what grade, what condition it is in, further de-rating for wet-service location, etc etc. Steel doesnt have those factors.

Regarding the 2x6's for decking.....you have to calculate WHERE the load is on the 2x6. You have to treat a 2x6 as an individual beam....with supports 64" apart. Too many variables are unknown. What is the track width of the tractor? Is it gonna track right down the 6x12 beams? Are you gonna deviate and have the load right in the middle of the 2x6....how far are the 2x6's cantilevered outside the main beams. What is the weight distribution on the tractor? Are you ever gonna go across with a loader bucket full and no ballast putting alot of weight on the small tires?

Too many unanswered variables to say conclusively that 2x6's will be okay.

 

[EddieWalker]

Hello all! I have a property divided in half by a creek. There is currently a 20' bridge in-place with concrete footings at each end with two 6x12 timbers for the span. The timbers are 64 inches apart and the current deck is made from 2x6s. I need to replace the 2x6s as they've had a good life and flex under the weight my my little JD X330. I'm wondering if replacement 2x6 boards will work or if I'll need to upgrade to 4x6s to support the live weight of a compact tractor.

Thanks for any and all input.

You really want the tires of the tractor to be directly over the 6x12 beams. If you can move your beams, then using 2x6's again should be fine. The only issue with the 2x6's is there isn't any support for them between the span of the beams, so there will be a lot of flex when walking across the bridge.

How long has the bridge been there? If it supports what you have, and it's working, then doing the same thing again shouldn't be a problem. I wouldn't build a bridge like this, but it's what you have there already.

 

[ArlyA]

Seen here is one of many bridge we built or helped on. From this experience, we now build them higher off the water, longer and stronger. Had to do them all over again!

 

[m2salmon]

Can you add an additional 6x12 in between the other 2? This would add a lot of stiffnesss and capacity.

 

[marhar]

If the 2x6's are shot why are the 6x12's still good?

That is a good question. There is a big difference between breaking a 2X6 with the front tire and breaking a 6X12 (which would be a catastrophic failure). Here is the south eastern US folks would use a burnt out mobile home for the base of the bridge.

 

[BoneZX14]

I just built this once Spring arrived. Five 4x6x16' (corrected, NOT 2x6x16 as mistyped before) pretreated timbers on edge to span across; resting on gravel/sidewalk blocks. 2x6x10' pretreated for the decking. So far so good with my little Massey (~1500lbs) and no worries pulling full size utility trailers across without going over the edge!

 

[tennmogger]

Being on some military vehicle and camping sites I see heavy truck beds taken off trucks so a camper can be built on the truck. These excess beds go for cheap. For example, FMTV beds come in 12.5 ft and 14.5 ft length and would be more than adequate for small streams. Prices run not much more than you would pay for just the lumber to build a bridge. I am attaching a photo of a bed I removed, but in TN. 8 ft by 12.5. Check the SELL threads of places like Steel Soldiers.

 

[fried1765]

Yup!
Agreed!

I just built this once Spring arrived. Five 2x6x16' pretreated timbers on edge to span across; resting on gravel/sidewalk blocks. 2x6x10' pretreated for the decking. So far so good with my little Massey (~1500lbs) and no worries pulling full size utility trailers across without going over the edge!



View attachment 702449

View attachment 702450

2x6 on a 16' span?
Lotta flex, even with only 1500#.
Not me brother!

 

[BoneZX14]

2x6 on a 16' span?
Lotta flex, even with only 1500#.
Not me brother!

Correction: 4x6x16', not 2x6x16'! (hahaha)
3' on each side is supported, 10' is in between.

Before adding the fifth.

 

[ArlyA]

As stated earlier, plan on high water. Higher than you can imagine or you'll be doing the same job again.