Bridge-Building

[jrb34]

Hi Folks--

I'm starting a small-scale timber harvest (spruce/fir/pine, about half sawlogs and half pulp) on my back 40 this year and need to replace a 50-year-old bridge across a brook. It currently spans roughly 35 feet, though 50 would be better for BMP reasons on the approaches. Equipment traffic will be light: small Kubota tractor with a winch, a Honda Foreman, logs on arches with smaller stuff dragged in multi-stem twitches. I'd like to get 20 years' use out of it for future firewood; 20 years should pretty much see me out--and 30 years at the most, given my cholesterol count.

Any ideas? Money is very definitely a factor; I had one bid from a major timber harvester for $15000, but then he wanted to drive his harvester and a tractor-trailer across it onto the sensitive wetlands I'm trying to protect, so his bridge design was considerably up-engineered for 100,000 pounds gvw. My max weight will probably be in the 3500-pound range--the tractor with bucket forks and three-point hitch forks both loaded with a pallet of firewood.

The current plan, from my low-impact harvester guy, is to drop some big tamaracks, bring in an on-site sawyer and have them ripped into 6x cants, which we'll bolt together (kind of like a stress-lam sandwich) into two 4x50-foot panels and drag into place on new timber abutments.

Options under speculation include a flatbed trailer or a railroad flat car, or finding used steel i-beams for girders and decking over that.



Thanks for your insights.

[markct]

a 53ft flatbed trailer would fit your needs perfectly i think, i would call around to some trucking companys and scrapyards and see if anyone has one they would let go cheap, it will outlast anything wooden and be good for alot more weight than you would need, i know where one is used and they regularly haul loaded haywagons weighing in at about 6 tons as well as tractors of about that same weight, and single axle dumps up to 26,000lbs, and im sure they would handle even more than that, just with the big trucks they are a little narrow, but just gota watch it, i imagine two side by side would be better if ya were going to regularly drive large trucks over it, but for anything up to a fullsize pickup one should be plenty wide

[Furby]

I've seen old enclosed semi trailers used as bridges, they just cut the ends out.
You can get an old one around here for a couple of hundred $ if ya don't mind the condition of the sidewalls and such. Can't belive it would be all that much trouble to cut the sides off, if ya have some equipment.

[RSteiner]

I don't know if this is possible but it seemed like a good idea.  In the town where I work a parking garage was being constructed.  As I walked by one of the precast sections of floor sitting and a flatbed truck I thought that would make a wonderful bridge.

I don't know if there are ever any "seconds" that could be purchased at a reasonable price.  All one would need is an abutment on each side to set one on and you would have a bridge a little over 8 feet wide that would last a life time.

I have built one using I-beams and a wood deck and one using hemlock logs for structural members.  I like the steel
I-beams better.

Randy

[Ron Scott]

A flat bed truck trailer or railroad flat car makes a a good bridge. They are often used as temporary bridges and moved from job to job where a temporary bridge crossing is needed to access a harvest area.

There wouldn't be anything wrong with leaving one permanent though.

It's best to place them on a straight access approach and not on a curve due to their narrowness and place safety markers on each end. Curb rails are sometime placed to help keep vehicle on the bridge.

 Be sure that their abutments are level and place them at least 3 feet above the high water mark if possible. Be sure to cable 1 corner to a large tree so you can easily retreive it should it be removed by high flood waters.

[IndyIan]

Just a note on cutting the top off an enclosed semi trailer.  On some the roof and sides is a lot of its strength.  

I watched one truck cut a corner and hit a building with a big metal overhang.  The corner of the overhang cut into the side of the trailer near the top, about 1/3 from the end, and for some reason the guy kept on going :.  I could hear 5 or 6 "ribs" pop and then the whole trailer sagged in the middle and the cut side basically folded open spilling the cargo out.  It was quite the mess and not driveable...   It came from Quaker oats so the stuff in it wasn't too heavy.
Ian

[Jeff]

Yea, I would think you would want a flatbed. Our chip trailers are a different story, as they are still 6 and 8 axle and the strength is from the frame, but if you look at some of those furniture haulers, they look pretty light.  I never thought of using a trailer for a bridge, but I had to drive to midland today for some testing, and after reading this, every trailer I saw, I was building bridges with it. :D

I wonder though, if the flat bed trailers with less axles, may have a stronger backbone?  On multi axle trailers, the axles are carrying the weight.

[Ed_K]

 In Logger's World they addvertise flatbed RR cars. 45,60 &90 ft. If you could get one of them it'd last 2 life times. We move a box car yrs ago, the owner got it for free. Only cost for a crane to take it off the tracks,set on lowboy and move to site.

[Furby]

Some of the semi trailers are pretty light weight, but there is no way the thin alum walls and roof are structual for the floor. The plywood on the inside is mostly for "bump" sufaces.
I'm talking about double axle 53' trailers. I drove 10k #+  hilos, carrying 2-6k# loads and the bounce was pretty light, and most of that was from the axels on the trailer.
I really can't belive the walls and roof add that much to the structure. Ya gotta also figure the roofs are designed for a snow load as well. That must transfer to the frame.
I'd just make sure ya look the frame over real good.
You can always add another layer of decking if the old one is in bad shape.

[jrb34]

Lots of good information here; thanks. It seems to me that changes in railroad material-handling must have left a lot of flatcars sitting around somewhere. I've seen them used as secondary road bridges in Montana. Getting one down through the woods and across the brook might be a bit of a challenge, though; with a flatbed trailer we could just back it down there, jack it up, cut off the undercarriage and winch it across on temporary sleepers or something, then lower it onto its cribwork.

Anybody done anything with built-in-place glue-lam decks or girders?

[Ron Scott]

The Glulam Bridges do a good job, but may be more expensive depending up the number of panels etc needed.

You might want to get a copy of the Alabama Cooperative Extension Publication "Portable Bridges for Forest Road Stream Crossings (ANR-1074) by Richard W. Brinker, dean and professor of Auburn University's School of Forestry and Wildlife Sciences and Steven E. Taylor, associate professor of agricultural engineering, Auburn University for more information on them.

For more information contact Auburn University: 334-844-1004; or email: brinkrw@auburn.edu

[johnjbc]

This is a picture of a bridge my Son in-law made out of an old house trailer frame. He broke the outside frame extensions off but left the center one's holding the fame rails together. The decking is 2" Hemlock and the rails are White Oak.
He drives his Kubota B2710 across it with no problems. 8) 8)

[Ron Scott]

Looks to be well done.

[SwampDonkey]

Check this out

Have a look at this skidding bridge

[Tom]

Talladega Machine Sales in Alabama has this bridge for sale.

 Bridge-Portable
 1150    
 
28928
 10'3" wide x 22' long, 2-axle.
 PRICE REDUCED  


http://www.tms-sales.com/equipment.asp

[jrb34]

I've seen plenty of those temporary skidder bridges here in Maine, but I'm looking for something more permanent for our 32-foot span, as I'm across that bridge with the tractor a dozen times a day in firewood cutting season, and across it on foot two or three times a day throughout the year.

The plan du jour is to reuse and beef up the current pressure-treated deck and laminate new girders from six PT 2x10s using PL500 construction adhesive, galvanized screws, and through-bolting after lamination. I should get 25 years out of that, which is pretty much all I need at 56.

[sawguy21]

In B.C, where I worked in logging, fish bearing streams were referred to as "riparian management areas" and were sacred ground. The regs for any kind of stream crossing were mind boggling. Be sure you are on solid legal footing even on private property.

[SwampDonkey]

sawguy,

I helps survey and classify alot of those streams in our cutblock layouts. I know what ya mean. They've become even a little more tight in New Brunswick too, but enforcement is really lacking.

cheers

[jrb34]

Rebuilding an existing bridge (one has been in that spot for 150 years or better), without changing the footprint, is a permit-by-rule event for Maine's DEP, as long as any groundwork done doesn't create erosion problems and adheres to published BMPs. It helps that the logger's day job is working for the DEP.

[sawguy21]

Because most of the logging here is done on public land the bridge plan goes through an exhaustive study. If approved, the bridge has to pass inspection before it can be used.
All the logs on the truck are marked with a lot number and the mill has to keep records. If the inspector sees logs from an unauthorized block or a species or grade that does not match the block plan, look out. Won't take them long to figger out there has to be a bridge they weren't told about

[Paul_H]

My first real day back this year was a large wood culvert over a creek around 200' above a 8" intake for domestic water and power for a land owner on the valley floor near the hot springs.It was very important to keep the creek clean from silt.








Looking back across the creek draw while the excavator swings the logs out of the way.Before excavators were common we would winch all the logs out with a 1 1/4"  winch cable on a D8.I prefer this way





Gary,the excavator operator placed rocks on both sides to hold the sill logs in place and then I cleaned the bark and dirt off where I was to notch for the side logs.






Notching done.Gary swings the logs into place.









The geotextile or "filter cloth caused us a lot of grief because it had been left out all Winter at the shop yard and was a chunk of ice that we couldn't unroll.It cost us a days progress because there was no other cloth available so we left it in the creek to thaw while we worked on other things.Finally it unrolled with some choice words and a lot of kicking while it was held up with the excavator.
It reminded me of skinning a Moose.







Done 8)

After we had finished and they filled in the approches I went down below to the intake and took a couple more pics







I took this last picture about 150' from the intake looking back over the valley at the landowner's property below.In the right hand side of the clearing is the landowners home and the cabin that Gary is renting.




There is just over 450' drop in elevation between the intake and the powerhouse below.

[woodmills1]

If you do go with a wood laminate bridge I think it should be more than 6" deep, I have planes for one using 2by 10 and 12 alternated pulled together with threaded rod.

[Jeff]

Paul, whats the estimated life span of a bridge like that? 10 years?

[ScottAR]

Great pics and great job!

What size is that Kobelco?  35ton?  I like the protection package
on the boom and dipper for the hydraulics. 

[jon12345]

When I was in college we built a bridge out of beech 6x8 and 8x8, it held the heaviest thing we had on hand, a loader. Can't remember if the loader was 14k or 14 tons though.



If I can find the disk I'll upload pics of the finished product.