Build bridge over creek

katyhorn · Sep 5, 2018

Ive been reading posts about this in this forum about this. one mentions splicing two 2x12s 16 ft long together but does not go into the details of how the spkicing is done. can anyone help here? thanks!

Granthol · Sep 5, 2018

Give us a pic of what you’ve got to cross and what the distance is. Someone can surely help with the right info.

goeduck · Sep 5, 2018

How long of a span do you need? We built ours years ago with old train trestle timbers and I think our span was about 40 to 50 feet.

dragoneggs · Sep 5, 2018

goeduck said:
How long of a span do you need? We built ours years ago with old train trestle timbers and I think our span was about 40 to 50 feet.

Wow... that was a project! Following along here. I love bridge building stuff and have a structural engineering degree... just no practical experience.

katyhorn · Sep 5, 2018

I will look for pictures and send them out.

katyhorn · Sep 5, 2018

The creek in our property has about a 24 foot span to cross. Initially it will be used for foot traffic, a riding lawnmover, and ATVs, but next year, I intend to buy a small tractor. The attached link is to a post that details what I need exactly. There are two posts on this page by Wayne who talks about splicing two 2X12 16-ft long boards, but does not provide the details and I want to make sure I do it right so as to not loose the integrity of the splice.

https://www.tractorbynet.com/forums/build-yourself/112243-wooden-bridge-span-question-3.html

Granthol · Sep 5, 2018

Check post 27 in that thread. He used 16 footers offset, meaning 8 foot of overlap in the middle of the 2 boards. He bolted every foot and glued it together also.

goeduck · Sep 5, 2018

dragoneggs said:
Wow... that was a project! Following along here. I love bridge building stuff and have a structural engineering degree... just no practical experience.

Before you get out your sliderule :laughing: we had some big arse timbers that were able to span the creek with nothing other than the two timbers and decking (also trestle timber). We run 15,000 lbs over it, no issues. The cattle usually just cross the creek direct since it is hard to calculate the weight at any one time. The bridge is only about 5 feet above the water.

oosik · Sep 5, 2018

katyhorn - good evening and welcome to TBN. Be very careful with your design. Notice the pics you posted show NO TRACTOR on that bridge. Also this is a clear span bridge - meaning, no center pier to carry the load. I would strongly suggest a review of your design by a knowledgable civil engineer acquainted with bridge design.

Tractor Seabee · Sep 6, 2018

oosik said:
katyhorn - good evening and welcome to TBN. Be very careful with your design. Notice the pics you posted show NO TRACTOR on that bridge. Also this is a clear span bridge - meaning, no center pier to carry the load. I would strongly suggest a review of your design by a knowledgable civil engineer acquainted with bridge design.

Amen, your requirement is far more complex than the 12-16' spans discussed here a lot. Always build more than you plan now; as time goes on it will suddenly not hold up when you decide it would be nice to take a load of gravel across with a 1 ton truck and trailer. Many have done your type using flat bed trailer decks. A 30'er can be had pretty cheap. I knew a guy who spanned a 30' cut with a RR flat car bed. The salvage value of the waste steel from wheels,trucks, and etc paid the haul cost and renting a trackhoe to move it. You can make beams from laminated 2Xs or plywood but a little engineering will probably pay off. You can take all the risj you want but others may not see it your way. Around here fire depts are refusing to cross bridges not certified by an engineer.

Ron

oosik · Sep 6, 2018

And I can take Ron's though one step further. Fire debt's refusing to cross non-certified bridges - buildings become ash - insurance companies refusing to pay on claims because the bridge did not allow the fire dept access to provide service. This can all roll up into one gigantic, nasty ball of wax - real quick.

katyhorn · Sep 6, 2018

Granthol, Thank you. If you look at the pictures, I think he first took two 2X12's 16-ft boards and glued/bolted them together. He did this again and ended up with 4X12's 16-ft long boards. Then he spliced them together. Are you saying he may have used another 2X12 by 16-ft and glued/bolted at the joint with an 8-ft offset?

katyhorn · Sep 6, 2018

All, my property backs up to the Colorodo River in Smithville Texas and is 11 acres about 350 ft wide (east/west)and 1350 long (north/south) down to the river. The creek runs about half-way accross the property (east/west). On the south side of the creek to the river is all floodplains, so I cannot build there, it is only for cattle grazing and for "fun" activities. The bridge will be only for personal use. Thank you for the warnings and will reconsider my plans. I was trying to do this as inexpensive as possible.

newbury · Sep 6, 2018

Well I was writing as you posted:

katyhorn said:
All, my property backs up to the Colorodo River in Smithville Texas and is 11 acres about 350 ft wide (east/west)and 1350 long (north/south) down to the river. The creek runs about half-way accross the property (east/west). On the south side of the creek to the river is all floodplains, so I cannot build there, it is only for cattle grazing and for "fun" activities. The bridge will be only for personal use. Thank you for the warnings and will reconsider my plans. I was trying to do this as inexpensive as possible.

BUT DON'T GIVE UP:
Obviously we can probably tell you, the OP, how to build a bridge that will carry a fully equipped Aerial Ladder Firetruck with a Tiller Tractor Tandem Rear Axle that is 63 foot long and may weigh 100,000 lbs.

And I daresay that many would love kibitzing on a project like that.

But like the second poster wrote - we need more info.
What's the entire span?
Span above flood plain?
What are the banks like?
And tons of more info.

And pics are needed also.

I used to work for the Army Corps of Engineers and among other things was involved in teaching parts of "hasty bridge" building.

And as I write this the following threads appear as "similar threads"
https://www.tractorbynet.com/forums/construction-equipment/175411-need-build-25-tractor-bridge.html
https://www.tractorbynet.com/forums/power-trac/72728-how-build-bridge-over-small.html
https://www.tractorbynet.com/forums/projects/175649-31-bridge-across-creek.html
https://www.tractorbynet.com/forums/build-yourself/277314-how-do-you-build-bridge.html
https://www.tractorbynet.com/forums/build-yourself/397353-building-bridge-over-creek-driveway.html

Building bridges is popular here.

So OP give us more info, your location, some pics and I'm sure we will do all we can to advise you on bridge building.

EddieWalker · Sep 6, 2018

katyhorn said:
The creek in our property has about a 24 foot span to cross. Initially it will be used for foot traffic, a riding lawnmover, and ATVs, but next year, I intend to buy a small tractor. The attached link is to a post that details what I need exactly. There are two posts on this page by Wayne who talks about splicing two 2X12 16-ft long boards, but does not provide the details and I want to make sure I do it right so as to not loose the integrity of the splice.

Every type of wood, every size of lumber, has a span table. This was created by engineers to know how far you can span a distance with a piece of lumber and how much it can support in the middle of that span. No matter what size lumber you use, there will be movement, or sag, or defection. It's all kind of the same thing, at the middle of that span, you will have the most movement. The longer the span, the greater the movement. This is also where the lumber is the weakest. Most span tables are for houses and what it will take to support people and furniture, a roof, or just insulation on the ceiling. Vehicles create another factor in this because of their movement, and greater weight concentrated on four points. Then there is the fact that once built, the wood will dry out, shrink, and twist to some degree over time. In five years, it will be different then when it was built.

Because of all these things, I would never consider splicing beams for a bridge. The longest 2x12 pressure treated board that you can get is 16 feet from most stores. Design your bridge with supports so that is your longest span. Just because somebody else did something does not mean it's a good idea.

Granthol · Sep 6, 2018

I agree,I was just summarizing what was done in the other thread. I would never splice without support below the splice.

katyhorn · Sep 6, 2018

Hello Everyone, Thanks for all the insight!

I like in Katy, Texas near Houston and our new property is in Smithville, Texas about 70 miles out. It will be our retirement place but for now, it is our weekend ranch with just an RV. I will be there tomorrow and will take lots of pictures of the creek, but for now this is the only one I have. It is a rope and a 2X12X20 board that I bought at the local lumber store for a temporary cross. The board now has an anchor in the middle of the creek. Like I mentioned earlier, I think to clear the creek to solid ground on both ends will like be 24 ft. Here is the pic.

Tractor Seabee · Sep 7, 2018

Like Newbury I have been involved in planning and building "hasty bridges" when in the Seabees. We did some innovative things. They were just that; keep the troops and cargo moving. Was not intended to last and was built with what we had available. That is not what the OP is looking for. I agree we are short on info and pictures to do a real planning scenario. If I understand the OP's desire he really does not want a HS-20 capability bridge. My RR tie stringers are still viable. Yes they need to be off the ground on sills or gravel. Used Waterfront structure timbers should be in good supply around Houston as well as RR ties. I assume this is not a "permitted" project so stamped engineer documents are not in the scheme. Like all of us he will be fine with our standard DIY "overbuilding" ideas.

Ron