Sizing of Steel I-Beams for Bridge

   / Sizing of Steel I-Beams for Bridge #1  

DocHeb

Veteran Member
Joined
May 24, 2001
Messages
2,384
Location
Michigan
Tractor
New Holland TC40D Supersteer
I've read all the "Building a Bridge" posts for the past two years. I know about telephone poles, railroad rails, culverts, and flatbed trailer frames being used as bridges for tractors to drive across. I know about floodplain, erosion, and footing problems. What I don't know is how to size the steel I-beams. The local distributor won't answer my question regarding sizing since he feels that would make him the designer of the bridge, causing him to assume more responsibility than he'd like. He knows I don't know what I'm doing /forums/images/graemlins/grin.gif.

What I'm looking for is two steel I-beams to span 16 feet between supports. These would be parallel and about 50" apart, giving the main support directly under my tractor's tires. The rest of the deck would be filled in with 3" thick ash boards - a very neat and low profile bridge. This bridge covers a small creek, and there are really no flooding concerns - but the bridge must "look nice" per the resident aesthetician.

There will be no need for car or truck traffic as this is on a back portion of the property. The question - what size steel beams are required to allow for for the dynamic load of a 5000 lb tractor/implement driving across /forums/images/graemlins/confused.gif

All suggestions would be accepted as what they are - free advice! /forums/images/graemlins/grin.gif ( i.e. I wouldn't hold any of the TBN engineers responsible for their design's structural integrity).
 
   / Sizing of Steel I-Beams for Bridge #2  
<font color="blue">( dynamic load of a 5000 lb tractor/implement driving across )</font>

Need some more numbers... what's the dead load weight?

I can possibly help with the "static" load numbers... /forums/images/graemlins/smile.gif
 
   / Sizing of Steel I-Beams for Bridge #3  
We've built quite a few for trucks, tractors, etc. We've never had any problem and always used the 12" tall I-beams. I would use these as you would never have to worry. If they support a 16k tractor they would support most anything you would need it sounds like. We just dig them flush into the ground and then you can drill your holes to put your boards on.
 
   / Sizing of Steel I-Beams for Bridge
  • Thread Starter
#4  
Now you've done it - you've exposed that fact that I really don't know the difference/significance between static and dynamic loads! /forums/images/graemlins/grin.gif I just figured that a moving load required a bit more "fudge" in the calculations.

I guess the static load would be ~5000 lbs for the tractor, plus the weight of the beams & decking? (As a physian I'd prefer to not use the term "dead" load.)
 
   / Sizing of Steel I-Beams for Bridge
  • Thread Starter
#5  
Your suggestion reflects the approach that I've generally used in the past - just make it big! I was looking to keep the size of the beams down to a minimum in hopes to decrease weight and cost.
 
   / Sizing of Steel I-Beams for Bridge #6  
If someone has a program to determine beam size -- I'd be happy to learn what size beams I would need to span 40' and support a fire and cement truck (loaded).

I am not having much luck locating anyone who can help me design my bridge. I guess I'll just try and design it on my own, and then have the MDE (Maryland Department of the Environment) tell me what is lacking in my design. /forums/images/graemlins/confused.gif
 
   / Sizing of Steel I-Beams for Bridge #7  
Dave:

For a 40 foot span and the use you have stated it will end up having to have a stamp of approval from a certified individual. Best just farm it out.

Egon
 
   / Sizing of Steel I-Beams for Bridge #8  
Gatorboy,

I just took 3 42' long and 14" tall ones out of an old barn that I was restoring. They had taken out alot of the rotted posts underneath that was holding the floor up and put those beams across to hold it up. I regularly drove my 4430 and baler, mower conditioner, disc etc. in there with no problems. My dumptruck I put in there this winter while I was rebuilding the motor and no problems there either. I will give my brother a call and see what he says for sure it should be. He's a construction engineer and should know.
 
   / Sizing of Steel I-Beams for Bridge #9  
I can remember drivin' two shires and a loaded wagon of hay across a couple of 100 lb. railroad rails, set up just like Cowboy Doc described. I don't imagine the span was over 10 feet though, and I doubt even those big horses outweighed your tractor. Our 4" oak planks were not fastened to the rails, and once in a while we had to go downstream to find them. /forums/images/graemlins/tongue.gif
 
 
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