I need to build a bridge to the main entrance of my hay barn. There is a 6 ft. ditch between the ground and the barn to keep soil pressure from the barn wall. The span of the bridge is about eight feet and I need to be able to drive my pickup truck across the bridge – but not necessarily into the barn.
I was considering using pressure treated 2×10’s for the joists from the barn to the bank, 2×6’s for the deck perpendicular to the joists, and 2×10’s running on top of that from the bank to the barn for the truck wheels to ride on. The joists will be on 24 in. centers except right under the wheels where they will be doubled and on 12 in. centers.
Is that sufficient for the load?
Larry
Replies
Is your truck made by Tonka ?
Is your biggest load likely to be a few marshmallows ?
: )
Quittin' Time
Maybe, but if it isn't it might be a hard way to find out. Since you are going to be full of hay and parking on the bridge I would want to err on the side of safety. Maybe building a support wall underneath. What size beam will the barn side of the bridge be secured to? Have you considered working with railroad ties?
Half of good living is staying out of bad situations.
Your right, driving my truck onto a completed bridge is no way to find out if it is strong enough. The barn side is a 10x10 beam, but I plan to augment that with a post under each wheel track. I could fairly easily build a mid-span support for the joists reducing the span to 4 ft. Do you think that would be strong enough?
Yes, but how do you spell disclaimer.
I realize that you probably don't want to get really involved in the hay bridge as in a slump 4 concrete pour with metal Ibeams:) I would think IMHO that a wall underneath shortening to 4ft span is in the right direction. If in doubt triple the 2x10s instead of double under the wheels or even go to triple 2x12s since extra cost isn't that much more for blessed piece of mind. When parked full of hay, where will the wheels be on the bridge in respect to the support wall?
'Course keep in mind that I'm just a homeowner DIY. My big descision of the week is what chainsaw to buy after studying the chainsaw thread. Got it narrowed down to Husky or a Stihl. Ha! Like those no brainers.Half of good living is staying out of bad situations.
Larry, So what did you finally decide to do?
Half of good living is staying out of bad situations.
rez,
The only thing I have decided for sure, is not to find out if it is strong enough after it is built! I tried searching the Internet to see if I could find tables listing alowable loads for wooden beams. So far I've found a lot of tutorials about stength of materials but no easy lookup chart. Surely there must be an engineering table where this can be looked up.
The other thing I considering is to build a simple test jig. Build two protype beams and deck for just one wheel. That is two doubled 2x10's a foot apart with 2x decking on top. Then support this at each end just a couples above the ground. To test I slowly drive two wheels of my pickup on it and measure the deflection. If it breaks the beam is all that is broken - not my pickup.
What do you think?
Always good to test without consequence. But thinking of your bridge I fear commenting specifics since I'm not there and so many variables come into play coupled with the risk of calamity if not done right. But it sounds like you're going to do this so I'll give you my two bits.
What size hay hauling truck are you planning for? Is it a normal truck bed with side posts or a large flatbed dually. I think we are talking about a lot of weight involved here. Normally when I'm in a big home project like this with risk I intentionally over- engineer and beef things up to the point where it will work no matter what. Usually more involved but half of good living is staying out of bad situations. I picture a big load of hay leaning over to one side. Truck loaded till you can't put anymore on there. Late at night before rains come, finish up the last of it. Put it all on one load. I don't want to trust an 8 foot span with 2x 10s. I'd say triple them minimum or triple 2x12s under those wheels and a wall underneath those 2x12s of which I'd park the wheels of the bed over the top of when I parked to unload. I don't know of the weight distribution with dual wheels. Single wheels I'd want to make sure I was right on the beam. Only 5 1/2 inches to play with when backing up.(late, dark, rainy 'hey joe am I on? tell me when to stop')
How long do you plan on using the bridge? You want 10 years trouble free? 20? Moving in a couple? Extra is always better in a case like this. I don't know how involved you want to get in a bridge or how much to spend. Or what natural resources you have available if money is a question. Temporary bridge could be built with old barn beams or cut some trees on your property or from a neighbor. Are you backing up on an incline when approaching the barn? Is the top of the hill from the ditch directly even with barn door? How often will you be using the bridge? For other uses than just the hay?
A little more data and I can shoot some more ideas your way. Any one out there who's done this before?
Half of good living is staying out of bad situations.
Edited 8/9/2002 9:49:25 PM ET by rez
2x10's 3" O. C., blocking between, every 2'.
Use plenty of nails
I mean PLENTY
No deck
skip the blocks and make it solid where the wheels will fall.
Can you say Over-build?!!
Mr TDo not try this at home!
I am a trained professional!
Much obliged!
Three inches on center, blocked every two feet - overbuild.
Willdo - I appreciate you advice.
Larry
I am not a bridge builder by no stretch but when in high school I worked on a farm and we had to build a bridge over a ravine that was longer across than what you have and it was to hold up a John Deere 4020 with whatever we were pulling at the time. We got some timbers that were creasoted, probably railroad bridge timbers, and then decked it with white oak rough sawn from the lumber mill. I know that this isn't much help but there must be someplace that you can get these timber and some specs on what they will hold.
We spanned the ravine far enough so that the timbers would not fall in, no concrete or anything but gravity to hold it in place.
Hell what's the worst that can happen? how deep did you say the ditch was?
Doug
There we are Larry. Now were cookin'!
Half of good living is staying out of bad situations.
Heres what I did with a similiar situation. Had to get a farm tractor with attachments over a small stream, 10' max. Built a 7' wide bridge with W8x18's steel beams spaced approx. 16" apart. Used plates welded to the webs of the beams at midspan with holes for 5/8" bolts ( 3 per ) and tied them together with plates. We couldn't put in Sonotubes due to the water filling the holes so we bought concrete parking lot barriers ( approx. 5" x 5" ) to use on each side of the stream and expansion bolted the beams to them. Laid a roughsawn 2 x 4 hemlock on top flange of the beams and bolted them down with carriage bolts. Then nailed 2 x 8 roughsawn hemlock down as a deck. Drove the loaded tractor on and had deflection of 3/16". It's been there for 3 years now. Still looks good. We probably should of screwed the deck down but we were wayyyyyyy out in a pasture with no power. Hope this helps.
Dana
Salmon Falls Housewrights