Bridge Questions

[timbatrader]

One way I have seen old steel bridges up graded is to pour a concrete deck on top of the steel frame if the deck is attached rigid via a lot welded attachments the deck becomes the top cord of the beam in compression the steel the bottom in tension. The depth of the beam is quite a bit bigger =stronger I have seen bridges rated 10 ton go up to forty ton using this method

 

[EddieWalker]

This is one of those things that sounds easy, but requires a profesional knowledge of soild, erosion and water flow. The span is easy, what is complicated is figuring out the minimum size footings that you need to support the bridge under worse case weather situations. How deep, how wide, how tall and what materials to use, along with how it needs to be anchored and held together.

Just because you find a bridge that already exists does not mean you can just install it where and how you want. If you don't get the footings right, it will fail on you.

This isn't a do it yourselfer and it is very much not something that you can get advice on how to do online without anybody know and being familiar with your exact location and conditions.

If you are going to do this, talk to several engineers and listen to what they tell you.

Good luck,
Eddie

 

[CurlyDave]

You definitely need a structural engineer. Possibly also a soils engineer to get the footings right.

It is false economy to try to do without this.

The engineer may well pay for himself by suggesting a more economical way to make the bridge.

Once you have the plans, you can build it yourself, but go over every step before starting and have periodic inspections by the engineer.

 

[timbatrader]

I am in the process of building a 36-meter bridge replacing a ford access to my house while I agree you need an engineer before finalizing your design. I recommend you use all means possible to research possible options. Most engineers will suggest the standard proven designs. Often there are other options using second hand spans and reinforcing the excessing abutments etc. that the engineer can do the calculations to confirm and can be cheaper/better These options are things the engineer would not offer to you unless you do the research first

 

[tkappeler]

Check out these two threads here.

just-another-bridge-project.html

and I need a new bridge. This one was very detailed into the costs, considerations, alternatives, etc.

Get the engineer involved.

 

[tlj87]

Thank you all for your responses so far! I learn a lot from this forum and I thought it would be neat to throw this idea out for discussion and see what others have to say.

I do plan hiring an engineer and obtaining all necessary permits, etc. This is one of those projects where it needs to be done once and done right. I am under 30, so this bridge needs to hold up for some time.

**
The concrete low water crossings look nice, but I am not sure that this would be ideal for year-round access in this case as it would not raise the level at which a car crosses enough to justify the cost.

Large culverts, particularly concrete box culverts (vs. steel/plastic pipes and gravel), may be a viable option. High enough to still be able to cross the stream during 90% of the time, but able to allow water to flow-over if a severe flood occurs without washing out.

An elevated steel structure (similar to, but more substantial than what we currently have) might be the way to go if an existing bridge (i.e. flatcar) was brought in and properly placed and secured. Otherwise, a new steel structure may be prohibitively expensive? Perhaps the only option?!

 

[Ken45101]

You also need to know maximum flow for the creek. 1-3 times a year, the creek goes over our bridge. The county engineer did a calculation for me and said that we really needed twice the capacity. Fortunately for us, our old bridge is solid and dumping rip rap and covering it with concrete has protected it.

Down the road a piece, a guy put in nice solid concrete piers and had a semi flat bed trailer body set on the piers. He built up the approaches to it. The first good storm washed out the approaches and shifted the flat bed a couple of feet. The next good storm washed it out entirely. The flat bed is buried a couple of hundred feet downstream with just the tip of it sticking out. The concrete piers are still in place. It's been that way for five years now.

 

[DKCDKC]

I have two crossings on my heavy stream. One is a ****, which is more than you want. T'other is simply a few culverts in the stream with concrete encasing their ends and stone in the middle. High water goes over w/o damage. Lasts forever - and costs relatively little. And you can do a lot of the work with your tractor.

 

[MotorSeven]

I'd let the foot bridge remain & use large culverts covered with concrete for vehicles. Culverts will be the cheapest and easiest to build & done right they look pretty cool.

Keep in mind if/when you have such a big flood that it floods that field you will have no approach to a raised traditional type bridge anyway. We have a creek to cross to our place, 35' bank to bank. The country replaced our old steel I-beam bridge with a new concrete one a few years ago. The pasture will go under water 2-3' deep one one side so we just have to sit back and wait until the water recedes, usually half a day or so.

 

[Kyle241]

I agree with the culverts and covered with concrete. Having a bridge built sounds great and will look cool but I think very expensive. Would like to see how you get on with this project so if you can keep us updated, that would be appreciated!