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Leesburg, Ohio | We are replacing an old bridge this summer on one of our farms. The span is 25 feet. I need to know what size beams to use on what spacing to make it safe for loaded semis to cross.
We have taken loaded semis across it for years with no problems, but when replacing the wood bridge plank deck last year, we discovered the web on the end of many of the beams was rusted away. Made be a bit leery of crossing with heavy loads.
Right now it has W16x36 beams (nominal size 16"x7"x7/16"flangex5/16"web, weight 36lbs./ft). They are spaced 2' on center, and X-braced every 8-10', and about 2' on each end of the beams rest on a level concrete abutment. The open span is 25', but the beams are almost 29' long, including the length that rests on the abutments. The deck is 3"x10" rough-sawn oak bridge plank. It is 20' wide, so it takes two ten foot plank to make up the width of the deck. One half of the bridge width (the west 10' lane) has a center pier supporting the beams, but I will probably use the same size beams all across the entire width.
The current design lets the heavy plank spread the wheel loads partially to adjacent beams.
Every search I do on the web just takes me to more search engines, or beam calculators that cost $40 or more to download.
Where can I find loading charts?
Edited by KDD 6/14/2017 21:36
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MN | When trying to size beams, I have had good luck calling bridge builders or used steel yards. They usually have an old dude around there that has been around forever that can tell you what a beam will hold, or what beam will fit your bill. Other than that, you can get an engineer to figure it out and stamp the drawing for some piece of mind. |
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SEON | From one of my old college books. It's been 30 yrs so don't ask too many tough questions LOL. I bet these old books are available on eBay.
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Leesburg, Ohio | OK, thanks, but I will need some help getting from your book to "will a bridge made of W16x36 beams on 2' centers and 25' span support 90,000 pounds?"
I'm not an engineer. Again, thanks! |
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SEON | KDD - 6/14/2017 22:53
OK, thanks, but I will need some help getting from your book to "will a bridge made of W16x36 beams on 2' centers and 25' span support 90,000 pounds?"
I'm not an engineer. Again, thanks!
Does it really need to support 90k? What are the axle weights and spacings that will be on the 25 ft span at one time?
Also, you've been driving across those beams for years? Why not use the same size?
It sounds like the current design uses a center pier on one lane of the bridge, presumably reducing the span from 25 ft to 12 ft? I'm guessing that's the loaded lane.
I might give some thought to repairing the existing rusty webs if it's possible.
Just some things to consider.
.
Edited by rank 6/15/2017 00:12
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SW Ohio | Ken I am no engineer but Dad was. Our bridge spans 30' with the beams 32', we redid it the 80's with used 14" x 32#???, six beams for 16' width, 3x4 lumber on top 16' long. Turned out the beams came from a burnt building and were not perfectly straight, this led to the boards flexing with each other on every pass of a truck, put a 1/4" steel plate over the center 8' but after many years the boards kinda disintegrated. We (without Dad, he was gone) redid it again a few years back, bought four new 14W36 beams ( a little more than the old ones that dad said were twice what was really needed) and regular treated 4x4's, added a full steel plate over that just for overkill. The bent beams never failed but were rusting badly in places, had no cross connections except one 2x2 angle in center span at the bottom, this model had one load over it that grossed 130,000 on a 40' tandem flatbed (don't ask). This whole project replaced the bridge that I grew up with, it was 32x 14 with only four 10" by not very heavy beams in the middle and 10" C channels on the sides, covered with 3x10's and a three inch layer of blacktop on top of that. We would ship out maybe a couple semi loads a year but the tandem milk truck went over it every other day. When the webs of those 10" beams had light showing through them was when we decided to replace the whole thing, it never failed but was getting scary.
short version, you really need an engineer to calculate the sizes, it is not something found in a table. That said it sounds like your old ones were big enough, just replace with similar ( and throw some cheap paint on them!) |
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central - east central Minnesota - | KDD - 6/14/2017 21:35 We are replacing an old bridge this summer on one of our farms. The span is 25 feet. I need to know what size beams to use on what spacing to make it safe for loaded semis to cross. We have taken loaded semis across it for years with no problems, but when replacing the wood bridge plank deck last year, we discovered the web on the end of many of the beams was rusted away. Made be a bit leery of crossing with heavy loads. Right now it has W16x36 beams (nominal size 16"x7"x7/16"flangex5/16"web, weight 36lbs./ft). They are spaced 2' on center, and X-braced every 8-10', and about 2' on each end of the beams rest on a level concrete abutment. The open span is 25', but the beams are almost 29' long, including the length that rests on the abutments. The deck is 3"x10" rough-sawn oak bridge plank. It is 20' wide, so it takes two ten foot plank to make up the width of the deck. One half of the bridge width (the west 10' lane) has a center pier supporting the beams, but I will probably use the same size beams all across the entire width. The current design lets the heavy plank spread the wheel loads partially to adjacent beams. Every search I do on the web just takes me to more search engines, or beam calculators that cost $40 or more to download. Where can I find loading charts? Ya, I think you maybe over thinking it too . . . . . Use what has been working, then add one more beam in the wheel tracks (each side of truck wheel track). Brace it so all beams work together and deck it as such also. It wouldn't hurt to have some tie's across the bottom of the beams, in addition to the X-braceing. The decking on top is what transfers weight to other beams. Farmer engineering would simple add an additional beam in the wheel tracks . . . . .. |
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| Call Gale at Champion Bridge Co. in Wilmington. I've always found them to be very helpful. |
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NC Iowa | Here is a bridge already built. It was used in a house moving project and no longer needed. My neighbor is an engineer and designed it. If you want I can get you his contact information.
https://masoncity.craigslist.org/hvo/6166004551.html
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MN | I do know from talking to an engineer, and the 70 yo owner of a beam salvage yard, for a beam to support my house, that a W10x50 will support 60k on a 20ft span. I would think that W16x36 on 2' centers would be more than enough to support 90k. Not to mention if you're talking 90k on a semi, you wouldn't have the full weight in the center of the bridge, well, ever. |
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Southern Alberta Canada | Here all the brides that size have been replaced with culverts. Might be worth looking into? |
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Sac & Story county IA | We had a place about that size that needed to be crossed by trucks. We used a multi plate culvert. Working good 30 years later. |
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Leesburg, Ohio | So, thanks for all the replies!
To answer a few points brought up:
No, a culvert is not what we need in this instance. It would need to be multiple huge culverts, and I think the expense of those and hiring the install would be prohibitive. Would probably require at least two parallel box culverts at least 12' square.
I don't absolutely require 90,000 pound capacity for loaded semis to cross, but it would be nice (but not absolutely necessary) if we could take a loaded grain cart across. 60,000 pounds of grain on a 36000 pound cart with 6-10,000 pounds of tongue weight on the tractor equals about 90,000 pounds on the cart axle. Our present cart is on tracks, so that make it less of a point load, but a wheeled cart would be close to that load, and either way, it is all on the bridge at once.
In all likelihood, we will use similar beams to what is there now. I did think about welding in some plates in the rusted-out sections of the webs, but really prefer replacement, and it would take a lot of clean-up of rust and scale to be effective.
The rusted out web ends has come from mud and cow manure sifting through the deck and accumulating on the top of the 2' thick concrete abutments where the beams rest. This is in a pasture, and the cattle drag mud and manure onto the bridge as they cross it several times a day. I have thought about pouring a concrete deck on top if we replace it, and never have to replace rotten planks again. Any suggestions for that?
I am talking to Martin's Farm supply in PA about the project. They apparently do these project all the time, and have a good supply of used beams, and the knowledge/experience to size it and weld the deck framing together, and deliver it. We will see what they have to say. I also have a good friend that is an engineer, so I may run it by him as well.
Again, thanks for the suggestions so far! |
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mowrystown ohio sw ohio | Ken you may be able to talk to someone at champion bridge in willington and they may be able to fix you up with the steel. Years ago I used them on help on building a dumpbed. And they had some cutoffs of steel that saved me some bucks |
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Where to find a steel bridge beam load chart?
