Building a footbridge
- Thread starter radair
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TNhobbyfarmer
Veteran Member
- Joined
- Dec 23, 2004
- Messages
- 1,185
- Location
- Middle Tennessee
- Tractor
- Kubota L3430 Polaris Ranger 500
I'm needing to build a bridge across a creek on my place, however it will need to be strong enough to drive a 6000 lb. tractor across. Will bar joists like you used be heavy enough or will I need to use I-beams? I will be spanning approximately 24'. I am not an expert at this type thing, but I do enjoy a challenge and the idea of doing it myself. I recently built a 27 X 24 pole barn and prior to that a 28 X36 log cabin, all without any previous experience. Both turned out very well in spite of my lack of formal training. How about the bridge? Would you suggest leaving that to an expert?
I don't think you'd have any insurmountable problems building your bridge, but I'd recommend getting a structural engineer to size your stringers. Bar joists come in many sizes, and there are a few factors involved, such as bridge width, number of stringers, and spacing of lateral bracing.
Many steel yards will spec beam & joist sizes at little or no charge. Even if you have to hire an engineer to check sizing, it's an easy calculation and should not be costly.
Many steel yards will spec beam & joist sizes at little or no charge. Even if you have to hire an engineer to check sizing, it's an easy calculation and should not be costly.
MotorSeven
Elite Member
Radair,
Excellent job on the bridge! Like TNhobbyfarmer, i also need a bridge but not for the tractor...just horses and 4wheelers. My problem is that in E. TN, the ridges are so close together that my creek goes to flood once or twice a year. And let me tell you, it pushes some serious debris downstream. My banks are 6' tall and the bank to bank is over 35'. I have been scratching my head for 3 years now over a way to get the thing high enough too not get caught by the debris, AND not cost a fortune. I am leaning towards pouring two abutments that terminate 4' above flood stage. Then span it with I-beams..that way nothing will be "hanging down". Anyway, it's one of the first things on the "retirement list" which keeps growing every day! /forums/images/graemlins/smirk.gif
RD
Excellent job on the bridge! Like TNhobbyfarmer, i also need a bridge but not for the tractor...just horses and 4wheelers. My problem is that in E. TN, the ridges are so close together that my creek goes to flood once or twice a year. And let me tell you, it pushes some serious debris downstream. My banks are 6' tall and the bank to bank is over 35'. I have been scratching my head for 3 years now over a way to get the thing high enough too not get caught by the debris, AND not cost a fortune. I am leaning towards pouring two abutments that terminate 4' above flood stage. Then span it with I-beams..that way nothing will be "hanging down". Anyway, it's one of the first things on the "retirement list" which keeps growing every day! /forums/images/graemlins/smirk.gif
RD
Renze
Elite Member
I have a program called PC frame, which is rather old but it works.. It is used to do structural calculations including the bend through of the beams at a given load.
I could send it to you but it is in Dutch so i dont know if you will be able to work with it... /forums/images/graemlins/crazy.gif
I could send it to you but it is in Dutch so i dont know if you will be able to work with it... /forums/images/graemlins/crazy.gif
Yes, maintaining adequate freeboard is critical, as fast-moving debris can do major damage. We were fortunate that this project site has a big flat basin, so the water level fluctuates very little. Another bridge we did is a backwater area for a significant river, so although the water can come right over the bridge it doesn't move at all.
Here's a pic of that one (50' span) before the wood was put down:
Here's a pic of that one (50' span) before the wood was put down:
Attachments
MotorSeven
Elite Member
This bridge is very similar to what i will be building. My creek is so pwerfull, that it has washed out the county bridge. I kicked around a suspension, but that gets really involved....looks cool though! Thanks for the pic's! BTW, is there an easy formula for weight-span for using I-beams? Such as a 40' x 6'(finished width)that needs to carry a ton to a ton & a half ? I am curious as to the minimum size of the I-beams.
I have access to a couple of old county bridge beams, but the darn things are 45' and about 3' tall. I even went and looked at them, but geeze, moving them would involve alot of resorces. My neighbor wanted to winch them up ontop of his wrecker a frame and try and "drive them", but i think it would crush his wrecker like a Tonka toy. I guess it could be done with an set of axles and make a long trailer out of each one, but then swinging them into place is a 'nuther can of worms. /forums/images/graemlins/crazy.gif
Anyway, i think i would rather go your route, and be able to manage the smaller beams with a minimum of equipment, as i know that i will end up doing 90% of the work myself!
RD
I have access to a couple of old county bridge beams, but the darn things are 45' and about 3' tall. I even went and looked at them, but geeze, moving them would involve alot of resorces. My neighbor wanted to winch them up ontop of his wrecker a frame and try and "drive them", but i think it would crush his wrecker like a Tonka toy. I guess it could be done with an set of axles and make a long trailer out of each one, but then swinging them into place is a 'nuther can of worms. /forums/images/graemlins/crazy.gif
Anyway, i think i would rather go your route, and be able to manage the smaller beams with a minimum of equipment, as i know that i will end up doing 90% of the work myself!
RD
CurlyDave
Elite Member
Just out of curiosity, why did you pre-cast the abutments in your garage?
Whenever I had had a similar job to do I poured them in place using a form, which I always thought set them perfectly in the ground.
Maybe I can learn something here.
Whenever I had had a similar job to do I poured them in place using a form, which I always thought set them perfectly in the ground.
Maybe I can learn something here.
MikeD74T
Veteran Member
Motorseven, Take a look at this site. It has plans for prefab bridges up to 50' span with enough arch to solve your problem. They show two trusses but could be 3 , 4, 5 as necessary for strength/width.
http://216.104.173.251/index.html
http://216.104.173.251/index.html
