38 ft. Span Bridge Over Small Creek

I'm getting a chilly feeling about this one.

It might be the scariest post I have seen on here.

"we should hire an Engineer to design it"

A 38' free span design in a creek bed is not for the uninformed.

8000 pounds ??? That design will never pass the liability stink test.

Hire a Structural Engineer to do your "estimate" for you.....please....

fire, I understand your concern, but there was a log bridge here, before and i want to replace it, so as to be able to support a car/ truck , no more than 8000 lbs. I design simple structures for residential homes, but i just want to get some opinions on this project. thanks for your reply anyway. p.s. .. I might have worded my post a little wrong. sorry about that.

Off the top of my head, I would say that your minimum is around $100,000.

That's assuming that there isn't some endangered snail, toad or microscopic organism in the water.

Put your plan on paper and get signed permission from the browngreen-shirts, otherwise they will destroy your world.

When dealing with the people that, (may), grant you permission to do this, treat every moment of contact with them as preparation for court. Document/ record every conversation down to the date and minute, along with every word spoken.

My estimate for failing to look at these people as potential enemies?

Dunno...maybe a $10 million fine and 20 years in prison.
Documentation is key.

kamarat, this creek is over private property and is off of a private road and only to access my property. how in the world do you get $100000. you don't even sound realistic. I am a contractor by trade and an architect by profession, so I am not a backward fool. I appreciate you exxxxageration, but please only answer the question asked, which is for a beam size. thank you.

I own (fairly) remote acreage too. So, I am sympathetic to your dilemma.

But liability is a real consideration, even if the injured party is trespassing.

I'm surprised you haven't asked some associates for assistance here.

I still say use a 40K# design goal.

Good luck.

Let us know how it works out.

40 feet is a very, very long span to be unsupported. I assume a support in the middle is not possible?

Your planking may weigh more than the two ton/8,000# limit. Look at the weight of 5"x9'x40 feet of concrete.

Your insurance company will be your biggest impediment and maybe also a good source of design help.

I'd design for 40,000# if I were you.

Try some of these:

WebStructural

BeamChek Structural Engineering Design Software

lyn thanks for that info. I will look into that and use the 40k number. I will check out you link. thanks

Get some professional counsel on this, the best. Any civil contractor could do an estimate on this with not much of a cost. Get their proposal. Proposals are for free.

I'd say it's more like 20k. These are old numbers, but they won't have changed much.

A 15T truck, as reported in 1944 gives the AASHTO H15-44 loading.

13.5k for moment

19.5k for shear

OR

you can use a uniform load of 480lbs/ft per lane. Then you have to add in the weight of the bridge. There are heavier loadings, this is the lightest in my notes.

Your beams need cross members at intervals for lateral stability unless the roadway can provide it. You might consider precast concrete planks with weld plates where they sit on the beams (I think 2 beams would be better than 3).

These are balloons turned loose to dazzle you. Your engineer is going to want to know about the ground for his abutments. There are many considerations for him to make before he can make a recommendation.

Wow, who would have thought to look for 2nd hand bridges. Even if a used bridge does not appeal, the pictures give your basis for a design that has been proved.

A GA from me, this was my first thought as a solution. There are many instances in Australia where old semi trailers are used as farm bridges, and one where a stolen one was used as a bridge to enable quite large loads of stolen equipment to cross a creek.

As has been said, they can support quite large loads without much alteration.

You beat me to it..GA... I've also seen flatbed railcars used for bridges, but that would be a bit overkill in this application.

If using railroad ties, the ones Home Depot sells are 7" x 9" x 8', and weigh 160lb each. So that'd add about 8,100lb (distributed) to the load the beams would have to support.

5" reinforced concrete, 8' wide, would be about 19,000lb.

You'd better decide which you're going to use pretty early in the design cycle.

I moved a lot of ties back in the 60's. Never saw any that small. They must be making smaller trains now.

A suggestion: In my part of the world used flat-bed railcars are often used to span 40 foot distances across streams and drainage ways.

I have no idea what they are paying for the cars nor how much the transportation fees are for getting the cars form the rail yard to the site and for a crane to place them on the supports.

As for the cost of steel;

I would contact local metal recyclers to see if they have the sizes you need and what the cost is.

In this area the going price of used steel is based on weight, length, and type as well as demand and who the customer is.

My WAG for building a bridge at 40 ft. in length with used steel rated for 8,000# live loading in my area would be: $25K - $40K (Based on steel work on one of my recent projects for building an overhead pipe conveying trestle that was in 50 foot sections.)

Gondolas of the type with no ends can also be used. These are hard to find now but you might be able to locate one.

A gondola with the ends cut off can also be used. Using a gondola eliminates the need for guard rails or anything additional to keep vehicles from going over the sides and into the "drink"

One of several potential problems with using the gondolas, also flat cars somewhat, is the cost of transportation by flatbed trailer, perhaps even a lo-boy, and the rigging necessary to put them in place. Unless you have one yourself or access to one with the necessary capacity, cranes aren't cheap to rent with an operator.

http://www.therailmart.com/

http://www.therailmart.com/pages/Flat%20Car%20Order%20Form.html

http://www.sterlingrail.com/classifieds/Listings.php?type=Gondola&fsw=FS

Good Luck, Old Salt

Your 8,000 pound capacity might be a little short. This is stated elsewhere in the discussion.

Fire truck is the first thing that comes to my mind. Unless there is an easy creek ford next to your bridge (year around... consider spring runoff and winter ice), I have a feeling you should figger at least the 40,000 already suggested, maybe more.

Wow, you guy or gal, are amazing. I really appreciate everyones input. I have alot to base my decisions on. I I thank you guys for taking the time to give a reply. If anything else pops up, please add it as a reply.

Just a few thoughts. Beams come in multiple lengths of 5 foot interval. So 40 feet is generally a stocked length of bar stock.

Your looking for maximum stress in the beam to be less then the yield stress. This typically is 32Klbs/sqin. for hot rolled steel beams.

Also how much deflection do you want to limit the span to.

max stress (sigma) = MC/I (M=max moment from load and beam weight, C=1/2 distance to neutral axis, and I=2nd moment of inertia of the beam).

You want to get the lightest weight per foot, so look for the tallest beam your design can accommodate, and is available as off the shelf. Something like 21x44, 21 inches tall by 44lbs/foot length. 3 to 4 of these get into the realm of what your looking for. But the weight of the deck is something to be concerned with. As well you add in the weight of the beam. Also think of total beam weight, as you will need to have a crane or what ever method you think of to place them across the span.

44 lbs/foot @40 feet is 1760 lbs. Not too heavy, but not trivial.

As Lyn suggests design for 40Klbs point load for the live load. But also Doorman suggestion of a fire truck needs to be considered. As your rural, I'm thinking they have a tanker truck, and I have no idea how many gallons of water this carries.

Ignator, thank you very much. I needed that info, for my estimation.

38 feet is NOT a do it yourself job, hire a pro, you'll live longer

Surprised no one mentioned a precast box culvert customize it to the size you need.

Box culverts will run you about $500 per ft. I would do three 12' boxes each one is good for 15,000 lbs that's without a concrete pad being poured on top if you want. Estimated cost with everything $20-25,000. Installation would be pretty easy also. Approximately two to three days total.

As Doorman's concerns--what about fire protection? Will you have service trucks--septic, well, etc. A fire dept tanker might be the heaviest, so contact them to see what they have--and might have someday. 4000 gallons + chassis weight? Dead load? And don't forget a safety factor which some codes put on the load and some on the steel strength; we typically used 36 ksi for steel yield strength. The deck must firmly fasten to the beams in order to provide lateral support. A uniform load is easy to design, but a moving point load is important to check.

How correct you are! I was fire chief locally. Several years ago we had a welding shop/barn fully involved on a rural road. Problem was there was a narrow light weight bridge on the 1/4 mile driveway up to it and the residence. Couldn't get any class A's across it, nor tenders with water. Could only get mini-pumpers and brush trucks across the bridge. Owner said fuel oil trucks used it but we weren't about to drop an engine in the drink. 30-50,000# of fire truck is more than it could take. A 4,000 gal tender is 33,200 lbs of just the water alone!

Used the mini pumpers for exposures and control brands. Finally put the structure fire out by pumping from the swimming pool with utility pumps to the mini-pumpers and the brush trucks. The residence would have gone up if we didn't use CAFS for the exposure several times.

Good Luck, Old Salt

Not speaking for the OP, but no one has established the need for a fire truck to cross the bridge.

I have 40 acres that has no buildings, but great fishing and picnic spots.

To get there you must ford a creek. No one goes there if the creek is flooded.

Simple.

Also, since a log bridge sufficed before, who's to say?

Yes, OP hasn't stated a need for fire trucks but also hasn't stated that there is no need for them. He has said that vehicles will cross the bridge so there is one need for fire equipment to put out vehicle fires on the other side of the bridge. Other possibilities are lightning strikes, brush fires, etc.

Structures are still a possibility since he hasn't stated that there are none. Many things are possible that he hasn't eliminated.

Good Luck, Old Salt

Need or no need. Built it, and they will come.

Frankly, if any government agency finds out, DNR (Dept. Of Natural Resources) or EPA to name a few, they will demand where is the environmental impact study and such. Not to mention the local town assessor.

This sounds like a large project.

You beat me to it with that. Maybe the bridge is for a handy route and there are other ways on to the property for heavier traffic.

You well need a min of 4 beams. W24x160 or 200. Spaced at 3-0. You will meed to weld Diagonal bracing at 5-0 spacing or bolted diagonals too. Must have a concrete beating at the abutment ends. No need for support in middle. Camber the 38-0 beams About 3" should do it. Cost is about 1.50 per # of steel. I might be high on that cost. Check with a stuctural engineer 1st. I'm just suggesting this for now. Need two rows of Nelson studs on top of beams for concrete. No paint needed if you use A588 weathering steel or drill holes in top of beam and anchor with carriage bolts.

38 ft span. 8000 lbs. The I-Beams would be enormous. Consider a truss bridge. A competent engineer from a local engineering firm would be able to provide some preliminary designs and cost estimates for a reasonable fee.

You sound like you are in the business. There is a company called con/span bridge systems that we have used for projects in our area.
Might be worth a call to get an estimate from them.
con-span.com

After read all the great responses, I was thinking that maybe, i can conbine a few ideas that were listed here. Seems to me that 4- w24x44 with a flat bed trailer on top of that for a double support might be the way to go for me. Of course i will do all the checks and balances. The building dept says that they do not handle any bridges, so they gave me the number of the agency that handles these matters, and they said that so long as i am not touching the creek area, that they do not need to give me a permit and that i should try to put the new bridge, where the old log bridge used to be. The insurance company said that they have no requirement for bridges. So i guess i am almost in the clear.

Do us a favor. Take and post pictures here. Both before, during and after.

Good luck and Merry Christmas.

If you live in a rural area, then most likely you are served by a Volunteer Fired Dept.. Now, if your house is on fire, then how are they to cross over that bridge of your with a pumper truck and a tanker truck? A 8,000# Live Load is very insufficient.

A bridge or culverts need to be designed for at least a AASHTO HS-20-44 Live loading. Also, you should consider a wider bridge, not 9 feet. I would suggest at least 12 foot travel lane to accommodate fire trucks and movers if you should need to relocate. Precast reinforced concrete box culverts will undoubtedly be your cheapest option IF the local water commission permits disturbance of the stream bed and banks.

5-inch concrete slab is wholly insufficient to support truck wheel loads. Plan on having a bridge wearing slab thickness around 12-inches, unless you're able to install precast-prestressed hollow core concrete planks with a concrete topping.

Believe it or not, municipalities around the country ans Canada do remove old bridges and sell them. You may be able to procure one for a decent price, but be prepared to spend a good amount of money having it transported to your location, as well as rehabilitating the structural steel. Don't forget that you need to provide structurally sufficient reinforced concrete abutments and foundations to support the bridge superstructure! These must also be designed to to resist "scouring" by the flowing water in the stream bed, especially during flood events.

Yes, obtain the services of a licensed Structural Engineer who is experienced in bridge design and the permitting process. Talk to one before you go off on your own willy-nilly, otherwise you're begging for trouble and several major RESTARTS that will cost you even more $$$..

Not to throw cold water on your plans but you really should ask a structural engineer this question. It is not as simple as designing for an 8000 LB load. Bridges are designed with bridge cycles in mind. i.e. a car weighing 8000 lbs going 30 MPH loads the bridge a lot more than a static 8000 LB weight. Usual factors for a live load are +70% and there may even be a surcharge of 50% over that for impact. A car traveling at 30 MPH covers 44 feet per second therefore the instantaneous load on the center of the bridge is an impact load. So a bridge that is designed for an 8000 lb load is actually sized for 8000 * 1.7 *1.5 = 20,400 LBs. And the bridge cycles should be over 10,000.

The road to the bridge is an easment road, only 10 feet wide, so i am limited to one lane 9 feet wide max. The area defore the bridge is a limited small 8 foot wide road perpendicular to the easement road., which is why i would like to go with large light beams with railroad ties or a trailer bed on top. The trailer bed should carry its own weight.

. Jim I am planning to build it myself. Thanks gor the advice.

Picture a trailer with a 60,000lb bulldozer on it, remove the dozer, rear wheels, and truck pulling it, and I believe you might have your bridge. (might have to stack a dirt ramp on each end) your local house moving company might place it for you at a reasonable cost. Place a sign at each end regarding 'use at your own risk', depending on where you are, you might have to state this in multiple languages. I rail flatcar can carry 2 loaded 40' trailers no problem, I think that's much more than you need. you should be able to find a 40' flat for a reasonable fee, I can buy a roadworthy 40' flat here in Colorado for < $4000. The trailer bed will carry it's own weight plus...check the rating. Serviceable 40'er's with steel frames are being scrapped for 56'er's made of aluminum. Cut the ends of a van(enclosed trailer) off and you'd have a covered bridge.

Expanding on #43, thank you geraldpaxton, the following are sites which may be informative and/or sources of the units for a flat car bridge:

http://flatcar-bridge-for-sale.com/bridge-advantages/

http://www.arkansasbusiness.com/article/47580/camden-company-recycles-railcars-into-affordable-bridges

This next one is 155 pages of technical information, "Use of railroad flat cars for low- volume road bridges". Very easy to understand.

http://publications.iowa.gov/11691/1/tr421.pdf

http://www.therailmart.com/

http://www.prsx.com/index.html

http://www.sterlingrail.com/classifieds/index.php

http://www.jimdobbasinc.com/parts-and-materials/used-railroad-flatcars

Hope these help.

Good Luck, Old Salt

Are you renting a crane. At 8-10 ' wide your going to have issues with using it. More than likely you'll need two one on each end. Plus you'll need space to put the stabilizers out. Another thing you will need is concrete abutments on both side you're are taking about a lot of weight being handled at both ends from the trailer and pad whether railroad ties, steel plate, concrete, etc.

This is one of the main reasons why those of us with construction experience are stressing getting an engineer involved. There are way to many factors involved for a due it yourself project.

If the water commission has dictated to him that there be no "stream disturbance", then how's he to get a crane across the stream? Just saying.

You are correct on many accounts. The bridge is too narrow. The weigh is tremendous. He'll need adequate abutments with equally robust footings.

He's got so much on his plate and he doesn't realize it (yet).

I'm purposely staying out of this thread, 'cause peeps don't really realize the complexities of bridge design and construction.....they'll get burned for some very poor suggestions here.

I agree with you 100%. Just trying to stress like you and several other posters that this isn't going to be an simple go buy a trailer frame or some beams and just slap it in. It's going to take a lot more input from an engineer with knowledge of this location and project.

EGGACTLY!!!!!!!

"Eggactly", eh? Please explain that "word".

Just trying to be a little funny. It's the same as "exactly", but with some eastern upstate NY accent thrown in...

Just a tip. When asking for an estimate, or a ball park figure you may get a very high figure. Legislation here says that any estimate MUST NOT BE EXCEEDED in the final price. There was a practice of builders/contractors giving low estimates to win the job and then charging a lot more at the completion often causing projects to fall over. This legislation means a ball park figure will be high to cover the unexpected and will often contain the rider that it will 'probably be cheaper than this'. But it never is.

So I am saying, get some firm quotes. Unless your country/state doesn't have this sort of law.

Jim

Pennyworth. Sounds an interesting project, how about:
1. Asking the local council how they would tackle it? They may supply design and or materials.
2. There are lots of load / deflection tables on the web for guidance. Google I-beam loading etc.
3. Have you thought about expansion? Heat could push the bridge along a bit. :-)
4. Be careful of using old truck bodies. They have a life span and may have suffered considerable flexing.(fatigue.)
5. Have you considered slide off barriers? Protection for rain ice or snow.
6. Duty of care for visitors. Get acceptance for public liability.
7. A central support if possible would save a fortune in materials?
8. Possibility for suspension bridge?
9. Reconsider your design several times, preferably with a scale model.

Just a few thoughts, good luck. jt.

I've got a disease that keeps transforming me into capital cities... it's starting to Hanoi me now....!

I'm addicted to placebos. I'd give them up, but it wouldn't make any difference.....

Anyone who says onions are the only veg. that make you cry has never been hit in the face with a turnip...!

Another possible material for the bridge is the glue laminated wooden beam (Glulam). These are pine or spruce boards, such as 2x4, 2x6, 2bys, that are laminated together on the long sides and ends to provide a much larger and stronger beam than the same size solid wood beam.

One example is the Anthony Power Beam.

http://www.anthonyforest.com/pdfs/GlulamBrochure.pdf

http://www.anthonyforest.com/pdfs/PowerBeamBrochure.pdf

They are also available in pressure treated

http://www.anthonyforest.com/treatedbeams.shtml

They have several online calculators that can be used for ball park $ figures. Distributors will often make calculations for you. What ever you do make sure you have an appropriate engineer do the design and oversee construction for you.

I have seen these used for numerous long foot bridges and vehicle bridges.

http://www.dot.state.mn.us/bridge/pdf/insp/USFS-TimberBridgeManual/em7700_8_chapter07.pdf

http://www.westernwoodstructures.com/

http://www.woodcenter.org/docs/groen96a.pdf

This type would certainly be more expensive than the previously mentioned flat bed trailer but worth a look. They are also available with special configurations such as arches, long spans for churches, etc. They can also be laminated by you. I did this once by gluing arches for a 25' bridge to accommodate people and a medium size garden tractor. Caution though, it takes a lot of time to make the template, find suitable lumber, glue and laminate the lumber, and finding "friends" to help you with this. The cost of the beer alone is much more than you would ever budget for!

Good Luck, Old Salt

chilly2264, Good luck with the project.

By now, you have probably discovered a trait flaw of this forum that is epidemic.

We make assumptions. We never quit giving advice, no matter how little we know of the facts.

But, there are some really smart people here.

I'm usually one of the very first to admonish new comers to "seek professional help".

But, I know that if I needed to build a bridge I'd ask here, too.

I think you will do OK.

Just send pictures.

thanks everyone, i appreciate all the comments.. I really do. I still have not purchased the property and i am trying to decide if I should buy it. I was thinking to build a temp, bridge with a flat bed, and then I wanted to use 40' used conc. slabs, that was used on a highway bridge. the only problem i will have is taking the beams to the area of the bridge. so i am doing my research to see what I do. The property is beautiful, but I have to decide which way to go. This is why I thank everyone with negative and possitive input.

Maybe you can look at some prefab bridges.

http://www.cnbailey.com/products/Single-Row-Single-Layer-Reinforced-Triple-Row-1654787.html

<bye>

I can't help musing that building the original log bridge was doubtless a damn sight simpler and probably involved no calculations, consultations or paperwork....

Just sayin'

Del

(scampers off to hide in secret cat nest....)

and if someone fell off it, or through it, the only thing said would have been "dumb ass"

We now have no personal responsibility(if we do something stupid), must carry 'insurance' (in case someone else does something stupid), our fine government decrees we pay fee's so everyone gets a piece of the action before, while, and after it is constructed ...the simplest thing might be to knock a spot of the bank down( being careful not to spill into the creek) and just 'ford' the creek when necessary.

I remember on this very site, under the 'What is it', a picture of a large trailer house that fell through a bridge in a similar circumstance, and a posting of where it sits today,.... they just removed the bridge.

Bailey bridges were developed by the British during the first part of WW2. They needed a bridge that could be transported on trucks (trucks were much smaller 75 years ago) but allow tanks to use it. A English man named Bailey developed it and it was a huge success. It was used in the European theater for crossing river that the bridge had been bombed out or blown up. One of the best things about them is that only a few needed anything to set them on at the shore ends. Most of them could be set up at night and be in operation by dawn. Now they can be assembled mostly without large machinery such as cranes, etc. They were assembled on the shore progressively and pushed across the body of water or swamps.

As others have mentioned, they are now used as temporary bridges mostly since they are more expensive than conventional bridges but they are much cheaper when the whole economic situation of the area is considered due to a loss of a bridge. I have seen several assembled, a very interesting thing to watch.

http://en.wikipedia.org/wiki/Bailey_bridge

http://www.baileybridge.com/

Good Luck, Old Salt

There's an animated video here, it's a bit over long but you can scroll through the middle bit. There's also links on the same page to other bridge building stuff.

Now that we've got you softened up, we'll rent (not sell) you the Brooklyn Bridge!

LMAO!!!!!! I can sell ya the George Washington Bridge as well....it's slightly younger than the Brooklyn Bridge.

If you use bar joists or castellated beams, you may be able to set them by hand with a few friends. Both have load tables for sizing. Be sure to use bridging between the beams, especially at mid-span. If a crane is comparatively convenient, and a pre-caster is not too far away, use a concrete double Tee.

So, no need for a fire truck to cross the bridge?

http://pages.jh.edu/~virtlab/bridge/truss.htm

I had a similar problem and my solution was to install two rail platforms side by side

with adequate foundations each end this installation has endured fire trucks excavators fuel deliveries cement trucks

You only need a crane on one side for installation and your footings can be installed with a concrete pump also from one side

A simple hint is to build foundations to allow floodwater to not wash away on the lee side when the creek bed banks are compromised

So... has this project been done?? I was thinking to build a bridge in my property as well and found this forum. These conversations are already more than four years old though.... chilly2264 can you please let me know if you have started/finished the project or just gave up??

Don't be silly. Consult a qualified Structural Engineer to design this bridge.

The <...cost...> is a function of location, material availability and price, delivery, operative mobilisation, supervision, plant and equipment hire, accommodation and demobilisation.

At the moment, the forum doesn't even know which country this is in, and couldn't possibly provide anything useful against a specification, if anyone could call it that, of only six sentences.

Why a <...bridge...>, though? Why can't the <...small creek...> be forded instead?

As a professional structural engineer, I have designed this stuff for 50 years.

Find your nearest hollow core prestressed concrete slab manufacturer to get a quote for the longest span deepest most tension-steel slab they make, which is probably 40 feet long. 8000 pounds on a 10-foot wheel base (4000 per axle) as the design load with a 3 inch topping. They can probably recommend a crane company and a concrete contractor that can run some numbers for you.

Here's a guy I've been following for years...he's my hero....He owns a bunch of land in upstate NY in the mountains and runs a property maintenance business...He builds roads cuts trees and any other thing that comes along...here he is building a bridge like you describe...

Andrew Camarata...