thought you knew me for a minute, i was a locomotive engineer, any how i stopped by the steel place, gave him my Ideas, he came up with a w16x 58, he is going to call me on the price of the beams, and the subway grating, It is looking more like a flatbed trailer, some of them are rated for 80k, so at 7500 to 10000lbs is a breeze.
Building a bridge to cross stream
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LD1
Epic Contributor
I strongly reccomend you download beamboy. The beam he is going to quote you (which is probabally a W16 x 57) is WAAAY overkill and will cost $$$$. The last thing I would do is to take the advice of the person selling the material, it's just more money in his pocket if he can convince you to go twice as big as you need.
On a side note, about the technical info, I got pleanty comming as I finally got beam boy working, so bear with me.
Some background, Beams are rated for load in two ways,
1. Bending stress in KSI. Most beams are A36, which is 36ksi steel, and you are allowed a bending stress of no more than 24ksi, which has a good saftey factor built right in.
2. Deflection. L/360, which is the length in inches/360. In your case, you are allowed a deflection of up to 1.13"
I plugged some #'s into beamboy and this is what I came up with
Beam............Deflection...........Bending stress..........Max capacity
W12 x 30..........(.991)...................13.2ksi....................5700lbs
W14 x 26...........(.963)..................14.5ksi....................5800lbs
W16 x 26..........(.783)...................13.3ksi....................7200lbs
S12 x 31.8.........(1.08)...................14ksi......................5200lbs
I used a 5000 lbs point load @ 17ft (exact center). Using two beams that would give you a 10000lb bridge. Given that steel is priced by weight, I'd probabally opt for the w16 x 26, as it will be one of the cheaper ones listed and the strongest.
The beam he is quoting you will look like this
W16 x 57.........(.311)..............5.5ksi.......................18,200lbs
His beam would give you a 18 ton bridge.
And if you really want a 13 ton saftey factor, consider the W18 x 50 or the W21 x 44. Both would be a little stronger but save some $$$ due to less weight.
On a side note, about the technical info, I got pleanty comming as I finally got beam boy working, so bear with me.
Some background, Beams are rated for load in two ways,
1. Bending stress in KSI. Most beams are A36, which is 36ksi steel, and you are allowed a bending stress of no more than 24ksi, which has a good saftey factor built right in.
2. Deflection. L/360, which is the length in inches/360. In your case, you are allowed a deflection of up to 1.13"
I plugged some #'s into beamboy and this is what I came up with
Beam............Deflection...........Bending stress..........Max capacity
W12 x 30..........(.991)...................13.2ksi....................5700lbs
W14 x 26...........(.963)..................14.5ksi....................5800lbs
W16 x 26..........(.783)...................13.3ksi....................7200lbs
S12 x 31.8.........(1.08)...................14ksi......................5200lbs
I used a 5000 lbs point load @ 17ft (exact center). Using two beams that would give you a 10000lb bridge. Given that steel is priced by weight, I'd probabally opt for the w16 x 26, as it will be one of the cheaper ones listed and the strongest.
The beam he is quoting you will look like this
W16 x 57.........(.311)..............5.5ksi.......................18,200lbs
His beam would give you a 18 ton bridge.
And if you really want a 13 ton saftey factor, consider the W18 x 50 or the W21 x 44. Both would be a little stronger but save some $$$ due to less weight.
DaveOmak
Platinum Member
Knew a guy who built a bridge using a railroad flatcar. worked well.
Ld1 thanks for the info, i could not get beam boy to work on my computer, I called the guy back for a price on w16x26, he said your paying for a 35 foot beam anyway so i would cut it to size at the site. depending on price a flat bed trailer might come out cheaper?? thanks again to all
LD1
Epic Contributor
Depending on local prices in your area, usually beams cost about 75 cents per pound.
That would put two of them @ about $1300-$1400, and they would weigh about 900lbs each. Which is something to keep in mind when you are thinking about using a flatbed trailer. A couple of 900lb beams dont require near as large of equipment as a flatbed trailer that probabally weighs close to 10k
That would put two of them @ about $1300-$1400, and they would weigh about 900lbs each. Which is something to keep in mind when you are thinking about using a flatbed trailer. A couple of 900lb beams dont require near as large of equipment as a flatbed trailer that probabally weighs close to 10k
RedDirt
Gold Member
- Joined
- Dec 4, 2007
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- Northern Idaho
- Tractor
- Kubota BX23, Wards 16HP HST Garden Tractor, (previous) D2 Logging Cat
A number of years ago I built two bridges from flatbed rail cars. I believe they were 10' wide and 40+ft long. The rail cars were about $3000 delivered about 70 miles. One we picked with a juice boom (crane) and one was skidded with two D-6 Cats, one shoving and the other winching from the opposite bank. One had poured concrete abutments and on the other I used discarded/surplus highway center barriers the county was selling cheap, bedded on compacted road base then backfilled to within a foot of the top. One bridge used 4x12 pressure treated plank and on the other I used 5" thick concrete running plank (not full width because of weight).
The bottom line for the bridges were in the range of $6000 each about 20 years ago. We put loaded concrete trucks and loaded logging trucks across these bridges. The rail cars are very stout (and extremely heavy...to move and place).
I may be able to find a picture and there is a slim chance I still have sketches and calculations squirreled away somewhere. I'll look if you are interested.
The bottom line for the bridges were in the range of $6000 each about 20 years ago. We put loaded concrete trucks and loaded logging trucks across these bridges. The rail cars are very stout (and extremely heavy...to move and place).
I may be able to find a picture and there is a slim chance I still have sketches and calculations squirreled away somewhere. I'll look if you are interested.
JustGary
Silver Member
18,000 lbs is only an 18 ton bridge if he's using two of those beams, which wasn't clear if you just glance at that line. Otherwise, very useful info on beams.
I strongly recommend that you go with a number above 15,000 lbs. for your bridge. Your 7500 lb tractor will not just sit in the middle of the bridge. You'll drive it across fast enough to get some wheel bounce and other dynamics. In other words, the static load on the bridge is only 7500 lbs, but the dynamic load on the bridge is much higher since the load is moving. Stand on your bathroom scale and move your arms up and down to see what I mean.
Factor in the eventual rust, etc. and you can see why you want to start with at least a 2:1 "safety" margin. The cost of overbuilding it now is nominal compared to the cost of a failure later.
Of course, you may have found just the ticket with the railroad beams. More capacity than you can ever use at a price even I could afford!
Regards,
- Just Gary
