I need a new BRIDGE!!!

[Rowdy Raven]

Hey folks, Happy New Year!!!

OK, here goes, to access my property I along with a couple of neighbors cross a stream via a wooden bridge that was built in 1946. This is a low water bridge that goes under with every good rain. However since the farmers who built the bridge did it right, it has never washed out.

First the details of the bridge, in the middle of this stream which is 40' from bank to bank they placed a concrete block that is 12'w x 2'h x 2'd. Then they put locust stringers from the bank to the block 3 on the left then 3 on the right from each bank for a total of 12 stringers. Then the bridge was decked with rough cut 2"x8"x12' oak. On the approach side the bridge is about 16" higher than on the egress side which is just about stream level. The water under the approach side is the deepest, being about 30" deep.

Next, this stream flows constantly and is fed by numerous smaller creeks for about 5 miles before it gets to the bridge. Then when it rains there is a tremendous amount of runoff down the stream. The bridge which has the upstream side lower than the downstream side just goes underwater with each flood and then resurfaces as the rains end. We usually end up with tree limbs, trash and what have ya on the bridge or caught in the upstream edge. The 100 year flood mark would put the bridge under about 8 feet of water. Normally a good flood will put it under about 4' of water.

The bank on the far side of the stream is very low while the bank on the approach side is somewhat higher. About 3 years ago during a sustained flood the concrete block in the stream cracked in the middle and the upstream half settled into the riverbed about a foot. Of course the bridge settled right along with it. So now when we drive across the bridge the decking boards in the middle on the upstream side are submersed.

The decking boards have come off now and it needs to be redecked for sure and really the super structure needs to be reinforced or replaced. We have talked for 10 years about what to do... but now we need to move.

We have talked about I beams, tractor-trailer flatbeds, utility poles, etc for the stringers. For the decking we have discussed rough cut locust or white oak or black gum or using Military surplus Marsden Landing Mats. We also need to substantiate the bank on the high side to keep it from eroding away.

We don't have a ton of money to put into this, but we know we need to build it withstand flooding and to be able to support the Propane truck that brings us fuel.

Well there you have it... what to do, what to do...... I am open to your ideas and technical suggestions on how best to proceed. We will try to do as much of this as possible ourselves. We have access to a couple of tractors with FELs and a backhoe. Thanks in advance for your thoughts and input!!!

 

[rsewill]

Just how much money?

 

[Tractor Seabee]

Sounds like you need to raise the lower end several feet and maybe the high end too. To make the 100 year storm and still cross that is a lot of concrete and fill at the sills and approaches. Propane truck I am guessing is at least 10 tons or more. What about dump trucks and concrete trucks in the future? They weigh a lot more. Sounds like some engineering will be required for your safety and for sure if it has to be permitted by some AHJ.

Your truck frame and bed is a good idea or maybe look into an old railroad flat car frame w/o the wheels. A guy I know did that and it worked out well setting on concrete sills. Needed a crane to set it but in less than 1/2 day he had a working bridge. Of course you would have to pick a new crossing spot and build new sills first. Probably have to pump the concrete to the far side sill.

Ron

 

[Hollow]

You can get an old 80' railroad flat car and get the foundation as far away from the creek as you need, and you can drive anything you want over it.

 

[Rowdy Raven]

I like the idea of using the railroad flatbed, the site is about 20 miles from the railway station. Located beside the old bridge is a ford that we are now using. It works well unless there has been a heavy rain. We drive our SUVs across it and have had dump trucks come through there in the past. Hopefully we could get a concrete truck across there, and back.

I have permits from the Corps of Engineers and the Wildlife Commission for the repairs. Building this as a low water bridge that we know would flood is acceptable. One of the neighbors put in a swinging foot bridge a few years back that we use during floods. It is about 150' long and is above the flood mark.

 

[MarkV]

Wow, that sounds like a big and expensive project. Around here what I would be concerned about is fire trucks. If the fire department is called and doesn't feel like you have a certified bridge they will sit and watch the house burn down. I can't really blame them. Well if your insurance company finds out the fire department will not cross the bridge they drop you and if you have a mortgage, without insurance, they get very unhappy. I would also wonder what happens if there is a fire and the bridge is 4' underwater because of flooding.

Good luck and I hope you will keep us posted as you decide on a plan.

MarkV

PS. Sometime back someone on the forum bought a steel bridge from the county and had it set by crane on there property. The advantage was the bridge already had a weight limit set by engineers.

 

[MG1867]

Maybe a mobile home frame? If it would work it could be towed easy enough. Just a thought and It may not work.

 

[SHORT KID]

A mobile home frame wouldn't do much in that span I don't think. It would need a lot of reenforcing. The entry and exit should be raised and some structural beams laid with rough sawn planking put on. Some dredging upstream may be of benifit also. Good luck.
short kid

 

[Tor Arne]

What about an old flatbed trailer, easy to carry sturdy frame complete deck simply remove the axles when you get it in place.

 

[Jerry/MT]

Hey folks, Happy New Year!!!

OK, here goes, to access my property I along with a couple of neighbors cross a stream via a wooden bridge that was built in 1946. This is a low water bridge that goes under with every good rain. However since the farmers who built the bridge did it right, it has never washed out.

First the details of the bridge, in the middle of this stream which is 40' from bank to bank they placed a concrete block that is 12'w x 2'h x 2'd. Then they put locust stringers from the bank to the block 3 on the left then 3 on the right from each bank for a total of 12 stringers. Then the bridge was decked with rough cut 2"x8"x12' oak. On the approach side the bridge is about 16" higher than on the egress side which is just about stream level. The water under the approach side is the deepest, being about 30" deep.

Next, this stream flows constantly and is fed by numerous smaller creeks for about 5 miles before it gets to the bridge. Then when it rains there is a tremendous amount of runoff down the stream. The bridge which has the upstream side lower than the downstream side just goes underwater with each flood and then resurfaces as the rains end. We usually end up with tree limbs, trash and what have ya on the bridge or caught in the upstream edge. The 100 year flood mark would put the bridge under about 8 feet of water. Normally a good flood will put it under about 4' of water.

The bank on the far side of the stream is very low while the bank on the approach side is somewhat higher. About 3 years ago during a sustained flood the concrete block in the stream cracked in the middle and the upstream half settled into the riverbed about a foot. Of course the bridge settled right along with it. So now when we drive across the bridge the decking boards in the middle on the upstream side are submersed.

The decking boards have come off now and it needs to be redecked for sure and really the super structure needs to be reinforced or replaced. We have talked for 10 years about what to do... but now we need to move.

We have talked about I beams, tractor-trailer flatbeds, utility poles, etc for the stringers. For the decking we have discussed rough cut locust or white oak or black gum or using Military surplus Marsden Landing Mats. We also need to substantiate the bank on the high side to keep it from eroding away.

We don't have a ton of money to put into this, but we know we need to build it withstand flooding and to be able to support the Propane truck that brings us fuel.

Well there you have it... what to do, what to do...... I am open to your ideas and technical suggestions on how best to proceed. We will try to do as much of this as possible ourselves. We have access to a couple of tractors with FELs and a backhoe. Thanks in advance for your thoughts and input!!!

If it were me, I'd set the bridge so that it would not go under water. going underwater is what got you into the situation you're in. The drag from the water generates large forces that act in the direction that the normal bridge structure is the weakest-lateral bending.
Spend your money on raising the concrete abutments so this can't happen and use a railroad flat car for a bridge deck. You can then regrade the approaches to the new bridge deck height. As the population increases and more land is put in too housing, roads , etc , run off increases and these "100 year flood events" happen more often. To minimize the risk in loosing the bridge again that's what I would recommend. It will be cheaper than replacing the bridge in few years.