Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 37
  1. #11
    Veteran Member
    Join Date
    Jan 2002
    Posts
    1,927
    Location
    Home-1+ acres New Hope, TX / 24 acres-Fannin County
    Tractor
    JD 950

    Default Re: Sizing of Steel I-Beams for Bridge

    Chris-I have been looking to do the same thing with a 30' span over a creek. I found a book on structural design that gives some tables to do some calculations. The basic formula is W=(1795*A*D)/L where W is the greatest safe load in pounds in the middle of an I beam, A is the cross sectional area of the I beam in sq. in., D is the depth of the I beam in inches, L is the length of the beam in feet. Here are some typical I beam numbers;
    8" I beam (18.4 lb/ft) A = 5.34
    10" I beam (25.4 lb/ft) A = 7.38
    12" I beam (31.8 lb/ft) A = 9.26
    (these are the lightest weight beams for each height. you can get heavier beams with greater A)
    If you run the numbers for a length of 16', then you see the greatest safe load in the center for;
    8" = 4792 lbs
    10" = 8279 lbs
    12" = 12466 lbs
    That load would be any materials that went into building the bridge plus any weight you put on the bridge.
    I am not a structural engineer so I am not sure what all else should be considered. But it is a starting point. I am still working on it.

  2. #12
    Veteran Member
    Join Date
    Mar 2002
    Posts
    1,482

    Default Re: Sizing of Steel I-Beams for Bridge

    Just be careful when someone mentions using a 12" or 16" or whatever denomination I-beam, because depth is only one factor for the beam.

    I-beams come in (at least) three different sections: The regular I-beam that has a relatively narrow flange section (i.e. about 4" for a 10" tall beam); these are called "S" beams - S meaning Standard. The next is a wide flange section (about 10" flange for a 10" tall beam); these are called "W" beams - W meaning Wide Flange; There are also "M" beams which look like wide flange beams but are actually used for vertical pilings - I really don't know what the difference is.

    W-beams will span a much greater distance and support a much larger weight than their respective S-beam counterparts.
    Another big factor is WPF or weight per foot; all steel beams are available in many different weights per foot, reflecting relative strength and span ability; of course, there are common and uncommon weights, common being cheaper.

    What you want to do can certainly be done, but just be careful because a steel beam is not a steel beam is not a steel beam.

  3. #13
    Elite Member Gatorboy's Avatar
    Join Date
    Aug 2001
    Posts
    3,106
    Location
    Bel Air, MD
    Tractor
    Kubota M8950, Bobcat 873 SSL & Kubota ZD-331

    Default Re: Sizing of Steel I-Beams for Bridge

    Bill,

    Thanks for that link -- there is alot of useful information to be had.

  4. #14

    Join Date
    Jul 2001
    Posts
    735
    Location
    Southern Maryland
    Tractor
    Ford 1220, John Deere 770, Case 580E and Allmand TLB-35

    Default Re: Sizing of Steel I-Beams for Bridge

    These guys Corps of engineers are supposed to be the ultimate authority on bridges. Send them an email and see what kind of response they give you. Not sure if MDE will be more help or hindrance. While you're designing, how about one like the attachment?
    Attached Images Attached Images

  5. #15
    Elite Member Gatorboy's Avatar
    Join Date
    Aug 2001
    Posts
    3,106
    Location
    Bel Air, MD
    Tractor
    Kubota M8950, Bobcat 873 SSL & Kubota ZD-331

    Default Re: Sizing of Steel I-Beams for Bridge

    I am staying away from the Army Corps of Engineers (ACE). They are the ultimate DELAY and RED TAPE machine.

    One thing I have learned is to design a bridge that doesn't touch the water -- that way the ACE doesn't get involved. From what I hear, getting a permit from the MDE is a cakewalk over getting one from the ACE. In addition, if I design it myself to be built by myself, the MDE is more lenient than if some Engineering firm submitted the plans.

    I guess when I get to that stage, I'll let you all know how I make out.

  6. #16
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
    Posts
    19,314
    Location
    Nova Scotia, Canada

    Default Re: Sizing of Steel I-Beams for Bridge

    Usually The section modulus required for the beam choice will determine the type of beam chozen or specifically designed.

    Egon

  7. #17
    Platinum Member
    Join Date
    Nov 2001
    Posts
    889
    Location
    Green Bay, WI
    Tractor
    Kubota F2400, Kubota F2100, Farmtrac 360, Tool Cat

    Default Re: Sizing of Steel I-Beams for Bridge

    Is hiring a licensed Structural Engineer considered a bad thing? [img]/forums/images/graemlins/blush.gif[/img] [img]/forums/images/graemlins/blush.gif[/img] [img]/forums/images/graemlins/blush.gif[/img]

    Someone with a bigger tractor may also wish to use your bridge someday

    Considering the importance of this structure, soundness and safety should be worth a few dollars. There are many details that if not accounted for properly will severely limit the best of intentions.

    Good Luck

    Yooper Dave

  8. #18
    Super Member
    Join Date
    Apr 2000
    Posts
    5,673
    Location
    Cedartown, Ga and N. Ga mountains
    Tractor
    1998 Kubota B21, 2005 Kubota L39

    Default Re: Sizing of Steel I-Beams for Bridge

    DocHeb,

    Here is a low-tech way of thinking about it. For a short span like 16' and the 5000 lbs weight limit you mentioned take a look at a 12,000 lbs equipment trailer. Seems to me that the one I was looking at was built with 6" channel so I would sure think an 8" I beam would be more than enough.

    MarkV

  9. #19
    Silver Member
    Join Date
    Sep 2002
    Posts
    204

    Default Re: Sizing of Steel I-Beams for Bridge

    Obviously engineers have their place just like attorneys, but I don't want to spend the money to hire a structural engineer for a small utility bridge. As a biologist I work with a lot of engineers when permitting stream crossing structures for the state and most of them aren't cheap. When I was looking into designing a small bridge, the engineering costs were more than the materials for the bridge. This was to be a simple short span bridge to drive my pickup and tractor across.

    I know there are a lot of variables involved in bridge design work, but I really don't believe that it's that difficult to design a small utility bridge. Most of the bridges folks are talking about are short single spans that don't involve piers or piling or high traffic volumes, etc. I also think most of us don't want to just guess on a design, and we'd like to use sound design principles to design a bridge. When I've asked engineers in the past about this, I always get the run around about all the variables and safety ought to be worth hiring an engineer, etc.

    I don't mean to imply that anyone can build a bridge and I'd be the first one to hire an engineer for any bridge that is used for anything but a low volume, light load bridge crossing. It just seems to me that simple bridges like this are a matter of determining the varibles and plugging them into known formulas.

    "I'm not an engineer, but I did stay at a Holiday Inn once"

  10. #20
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
    Posts
    19,314
    Location
    Nova Scotia, Canada

    Default Re: Sizing of Steel I-Beams for Bridge

    When designing something like a bridge always Put "Third Party Liability" at the top of the priority list.

    Egon

Page 2 of 4 FirstFirst 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© 2016 TractorByNet.com. TractorByNet is a registered trademark of IMC Digital Universe, Inc. Other trademarks on this page are the property of their respective owners.