Steel I beam Load/applications

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Old 03-27-11, 09:51 AM
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Steel I beam Load/applications

Steel I beam Load/applications

Hi,
I am trying to find a simple answer to a complex question about which steel beams to buy. I have searched many sites; this one, in previous posts, has come the closest to answering my question, but not quite an answer I can use. I hope someone has either a link to a simple table that predicts center load by span by beam types, or knows of another approach, short of hiring an engineer.
I have an old bridge site with intact concrete abutments. I need to build a bridge suitable for a logging operation. The bridge will need a center load capacity in a 14 ft span of 10,000 lb and/or a full-length load capacity of 20,000 lb. As I will use two beams, each beam needs a center load capacity of 5,000 lb or 10,000 full length, whichever is the more demanding specification. I realize I am designing a static load for a potentially dynamic application, but I am including a significant margin of error.
I anticipate using 2 W10X12 or W12X14 steel beams.
Anyone know of an approach?
Thank you,
Chris
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Old 03-27-11, 10:45 AM
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Sorry, but this IS a question that only an engineer, specifically a Civil Engineer, can answer. Even if your bridge is on private land and will be used only by people of your choosing there are laws and regulations that must be followed. I know that I sure wouldn't the responsibility of failure on my shoulders and I AM an engineer.
 
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Old 03-27-11, 01:13 PM
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load capacities

Hi,
I appreciate your concerns.
Perhaps a question that smacks a little less of liability would be:
How can I find out the center load and full span load capacities of a W10X12 and a W12X14 steel beam in a 14” span?
Chris
 
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Old 03-27-11, 01:29 PM
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I wish I could help but that is outside my area of expertise and frankly I don't have a clue.

Good luck!
 
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Old 03-27-11, 05:01 PM
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Thank you again for your thoughts.
I have built several timber bridges of varying spans. They have supported a 10,000 lb (smallish) John Deere excavator. The operator got out, looked underneath and confidently proceeded across. However, when he exceeded a few miles an hour, an un-nerving “bounce” started to occur.
The woods up here (northern NH) are filled with logging road bridges. I always peek under when I come across them to see how they are made. Often they are just oak trunks decked with 4X6s. The abutments are one or two larger tree trunks set perpendicular to the road. Some, like the one I want to build, are a combination of wood and two or four I-beams. One logger I know has a railroad car deck that he places as needed. At 50 feet, it spans many wetland and most open water obstacles.
I am lucky, at this location, to start with ancient, but solid, concrete abutments and a short (14') span. There was a bridge here in the 1950’s. A few of the local people, my age or older, remember the bridge. A usable bridge at this location would keep the logging operation out of my paddock, where my current high capacity bridge is located.
I know I can build a timber bridge, but I can’t help but wonder if a steel or steel and timber bridge would make a cost-effective, more permanent solution.
Chris
 
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Old 03-27-11, 06:00 PM
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I've only been in New Hampshire once and that was just to look at the autumn leaves. I know that in sue-happy and (over) regulated Washington state an amateur-built bridge that was anything more than just a small footbridge over a mud puddle would be torn down by the authorities within a week.

I wish you well.
 
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Old 04-26-11, 07:44 AM
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Update

Update. It turns out there are pre-designed bridges available for specific spans. The state of Maine has some. I now am looking at their 18’ (open crossing up to 15’) version. These bridges come in pieces as “kits”. Isaacson Structural Steel, Inc. in Berlin New Hampshire builds them and has a library of suitable designs. These bridges are designed to carry a loaded logging truck, which can weigh up to 100,000 lb. For a great discussion with design specifications for a variety of solutions see
http://www.mlep.org/documents/tempst...tlandcross.pdf
Chris
 
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Old 04-26-11, 12:21 PM
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I am a Structural Steel Estimator for a fab shop here in MI. Being in sales i have seen and heard it all, but a question for you...are you planning on erecting the steel? What exactly are you planning on driving over the bridge or do you want an over kill for "whatever/whenever"? Whats the snow load in your area because we are not just talking live load here, we are also talking dead load. What do you plan on using to span from beam to beam (what the vehicles are actually driving on)? Flat bridge I hope, not cambered? How is the steel going to be attached to the "footings"???? Bearing plate that the beam will sit on and be welded to? Epoxy Anchored to the footing? Anchor bolts in the footings and hole in the flange of the beam to be bolted to? How long do you plan on this bridge lasting??? If its just to get your tractor over a creak to mowe your field and not going to cover the steel I would suggest the beams galvanized. You could also use Tube/Rectangular steel.

I am not an engineer nor do I have the letters after my name but like mentioned before you really need an engineer to tell you what you can use...once you answer all the questions I am asking. You dont want to have "bouncing" like mentioned earlier either.

Just an FYI...a W12x14 @ 16' will have a deflection of .46" just from its own weight. A 10x12 @ 16' is .30".
 
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Old 04-26-11, 01:36 PM
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Hi Krss144,
I have a timber lot on the far side of a brook from the road. Originally I was planning on building a bridge to accommodate the skidders (about 20,000 lbs) and load the logging trucks in a field, roadside of the brook. From what I can tell, a bridge that can accommodate the logging truck (100,000 lbs) isn't going to cost that much more. The 100,000 lbs bridge would accommodate any future use I might have for my land.
This "Maine" design uses 14 X 22 beams bolted together with strapping at three locations. It is designed to be assembled on site. The specified decking is 8 X 8 timber. The plans specify concrete abutments 18' wide, which is exactly what is there already. They show no anchoring.
My "bouncing" bridge is 12 X 12 timbers decked with 4 X 6s. It is a longer span. I just drive very slowly.
Mostly I was updating just to suggest anyone with a similar problem try contacting a company that builds bridges. They seem to already have designs. Also the web site I mention in the previous post has numerous solutions including pre-stress concrete bridges and the old "rail road car" 50' solution, although they suggest a re-enforcing technique. The article lists venders and prices (probably some what out of date) for many of these solutions.
Thank you for your interest,
Chris
 
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Old 04-26-11, 02:09 PM
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Steel bridge beams

Steel bridge beams
In case there is someone who might not know (it had to be explained to me), steel beams seem to be specified by a letter and two numbers. A W10 X 12 beam is an I beam (the W), 10 inches tall, which weighs 12 lbs per foot.
 
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Old 04-26-11, 05:34 PM
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Chris,

Thanks for that link.
I went through what you are except on a much smaller scale.

My "bridge" spans fifty feet but is only four feet wide for foot traffic and the occasional snowmobile or quad.
I am perfectly understanding and respectful of the engineering trade and feel they are right in protecting us from ourselves!

For my final design I took advice from a welder friend that gave me a pile of short steel rafters with a twenty four inch web.
Wound up with a pretty solid structure and a surprise test when my friends showed up and parked three quads, two dirt bikes and their riders on it!
 
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