strength of steel acording to thickness

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what is a good rule of thumb as far as the strength of steel as to its thickness? i hope i have it phrased right. like u gage wire acording to the amps u wanna tun thru it, theres gotta be a way to gage steel acording to the weight u need it to hold.....
Reply:It doesn't work that way. The shape and location of the steel has a large part to do with how much load it can carry. For example  beams are sized by depth and weight per foot. A W8x31 wouldn't carry as much as say a W 16x31, even though they contain the same amount of steel. The taller beam has the material farther from it's centerline, so it can take more weight and not bend. A truss built with the same amount of steel per foot, but that was 4 feet tall would carry even more load most likely.A truss works because the steel at the top and bottom takes the load in compression and tension. The middle part just needs to keep the top and bottom apart.Thats why engineers get paid the big bucks. Theres a bunch of complicated formulas that takes the shape of the steel into account and how far the steel in that shape is from the center line. It's posible to find some very basic tables, but usually they only cover very simple loading senarios, like if you wanted to size a beam to support joists in a house for example. More complex designs need to be worked out by hand or on specialized engineering programs..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Well, I could parrot what DSW said, because it's a pretty good answer, but I'd rather say that steel's "strength" (which I take to mean allowable stress) is imparted at the mill and fixed thereafter.  The shape allows a certain loading whilst not reaching the allowable stress of the material.  There are, in fact, many sites which will help the novice to design structures.  Also, there are many people injured and killed annually by such novice practices.  If you're designing something to hold a hanging potted plant, that's one thing.  Trailers, pressure vessels, and buildings are different beasts altogether.Yes, that is why engineers get paid the big bucks.
Reply:Nice work DSW, I think you pretty well nailed it for a basic explanation."Remember anybody could design a bridge to carry its load.It takes a skilled engineer to design a bridge that can just carry it's load safely.""The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Highly recommend you get a copy of this book,  Harbor freight sells it too.   full of specs for all the common metal size and shapes.  weight strength etc[ame="http://www.amazon.com/Pocket-Ref-4th-Thomas-Glover/dp/1885071620/ref=sr_1_1?s=books&ie=UTF8&qid=1310449738&sr=1-1"]http://www.amazon.com/Pocket-Ref-4th-Thomas-Glover/dp/1885071620/ref=sr_1_1?s=books&ie=UTF8&qid=1310449738&sr=1-1[/ame]This is a good book too.  will walk you through all of the common formulas for figuring out load, stress etc for common steel sizes and shapes used in trailer building.  when I taught HS shop class I used it a lot to show kids how math is important.  Applied Mathematics.   [ame="http://www.amazon.com/Trailers-How-Design-Build-Structure/dp/0914483323/ref=sr_1_1?s=books&ie=UTF8&qid=1310449842&sr=1-1"]http://www.amazon.com/Trailers-How-Design-Build-Structure/dp/0914483323/ref=sr_1_1?s=books&ie=UTF8&qid=1310449842&sr=1-1[/ame]Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:You obviously must know the difference between a sheet of paper and say a corrugated cardboard like a box. 1 is much more rigid due to its shape and bends. Same principle as explained above.  That being said there are all kinds of charts that show values of different types of structural steels like bar stock, angle iron, and channel iron. They can be found on the internet or most steel houses. Also some steel houses have and engineer on site you can consult with. But be warned there are many types of loads from  simple compression like a column to the more complex like torsional and cantilevered.  Give us and idea of what you are trying to figure out."Si Vis Pacem Para Bellum"Lincoln Idealarc 250 AC/DCMillermatic 251   Syncrowave 300   30A spoolgunLincoln MP210Hypertherm 45(2) LN 25(2) Lincoln Weldanpower 225 CV(4) SA200   1 short hood    SA250    SAM 400
Reply:Originally Posted by kolotYou obviously must know the difference between a sheet of paper and say a corrugated cardboard like a box. 1 is much more rigid due to its shape and bends. Same principle as explained above.  That being said there are all kinds of charts that show values of different types of structural steels like bar stock, angle iron, and channel iron. They can be found on the internet or most steel houses. Also some steel houses have and engineer on site you can consult with. But be warned there are many types of loads from  simple compression like a column to the more complex like torsional and cantilevered.  Give us and idea of what you are trying to figure out.
Reply:Originally Posted by dave powelson***Below is what midGAoutdoor's plans are as of 7-8-11:i am kinda new to welding. i have welded lots before on farm impliments and such but nothing that really mattered. i have a few cert. welders that are gonna help me out with some trailer idea i have for mu business Mid-GA Outdoor. my sister os one of them. anyways. my dad has a Century 230amp welder that is AC. i usually use 7014 rods. what am i SUPPOSED do use for this AC welder? He's simply designing and building trailers; needs just 'a little bit' of help.
Reply:Originally Posted by Teljkonbetter he ask than put out some thing danger. Even if the little bit of help is a alot a bit of help.As far as weight to gauge ratio its equal to one chicken per unit from 26 to 19 one pig per guage from 18 to 9 and one cow from 8 to 1 & zero can hold a elephant. Serously though your not taking into acount the the fact that each alloy is diffrent the thickness at which it can handle the same load can change as much as .02 probalby more ( I take that # from my work others may know of greater examples). You need to go out to where your going to get the best deal on metal for your work and do a little talking with them about what they have and how to obtaine a data sheet for the product they are selling. Not to say there are not averages or standards but if you want to know what your working with thats how to go about it. Plus I doubt DOT is going to take " this trailer is rated to around such and such lbs or about such and such. This is assuming your going to get DOT involved and try to meet specs. You could just go and sell a trailer but if some guy wrecks his **** at fault of your trailer or not and finds out his insurance wont pay cause the trailer isnt up to some Goverment spec he could come after you legaly or otherwise.
Reply:Originally Posted by wboldenWe can try to help you but you are treading in dangerous waters.....
Reply:Not trying to hijack this thread, but Kolot suggested giving the details and see if someone can help.I have tried to find similar information for a simple project. On my property is a wet weather ditch for run-off that separates my main yard from the back. I have thought about putting a very simple bridge to drive my riding lawn mower across so I don't get stuck in the mud. The span is 10', the height is only about 2' (just enough to get stuck and keep my mower muddy), and it would need to be about 5' wide. Just a flat platform type is what I have in mind. Maximum weight for me and the mower would be less than 1000 pounds. I figured on decking it with 2x8's or so. I could easily put vertical supports so the maximum span would be 5'. I'm interested in what would be the smallest beam that would safely carry this. Keep in mind - THIS IS NOT FOR PUBLIC USE. And it would be too narrow for anyone thinking, "Yes, but someone will want to drive a cement mixer across it one day". Pictures of your bridge would be helpful and interesting.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:An idea how heavy your mower is would help if you want to figure a minimum size..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:try Some 8"  I beam which will fit 8x8 railroad ties between the top and bottom of the beam nicely and make for a nice bridge.   will be plenty strong for what u want it forTiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:You could also use a section of culvert pipe instead of the bridge.
Reply:Could come up with everything from a culvert pipe to a suspension bridge but if you think about it, 1000 lbs is not much. Every landscaper you know is running down the road with 2 zero turn mowers on a 16 foot trailer. Those trailers are usually 3 or 4 inch channel. You could use something that mimicks a trailer deck with two end and one center support. Keep in mind you won't be able to drive a loaded dump truck over it , but a car or pickup goes down the road for many miles on a car hauler which isn't built real heavy. I believe you stated your span would be in the area of 10 feet. Even a deck on a house if built fairly heavy and not crazy heavy will hold you and 5 or 6 of your friends drinking beer,talking in a circle. That is probably approaching 1,000 lbs. just don't try to concentrate or point load that 1,000 lbs. Do you have a state park or puplic place that has a small walk bridge, give it a good look you will find it doesn't take much.     On the original post I did not know he was building trailers, best way is to see what works and copy it, plenty of trailers to look at."Si Vis Pacem Para Bellum"Lincoln Idealarc 250 AC/DCMillermatic 251   Syncrowave 300   30A spoolgunLincoln MP210Hypertherm 45(2) LN 25(2) Lincoln Weldanpower 225 CV(4) SA200   1 short hood    SA250    SAM 400
Reply:Hey guys, thanks for the good answers. DSW- the mower weighs 478 pounds, with overall width of 52". So I'm confident the total weight would be less than 1000 pounds. I like the idea of the 8" channel and cross-ties, but seems like too much money and overkill for this application. I have considered a culvert, but I like welding more than digging and just thought it could turn into a nice look for the property and an asset if it is done right. And I will probably have to find the main support components at the scrap yard to justify the cost, so knowing the minimum helps in evaluating my options. Good points about the lawn trailers and building supports. Maybe I can model the trailer and use lighter supports by adding a top rail. That would make it more attractive, too.Again, thanks for the suggestions and I hope this helps others in calculating the correct materials.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com