dyi engineering! how 2 figure load?
i know ,hire a engineer ,but i made a post about my garage the other day and everybody thought i ought to reinforce the ridge beam [so i can remove the rafter ties]so i’m thinking a steel i beam,but need to figure some loads and what size beam i need.so heres what i got ,24×24 garage, 4/12 roof . i’m thinking i figure load by sq footage [600] x25lbs a sg ft [i will double check that with city]=15,000 lbs. divide that by 2 because the outside walls carry half the weight =7500lbs. is that what this ridge beam needs to carry? i checked on a paralam they said i need a 3.5x 16 .i would rather use steel if possible,just trying to see how big a beam it will take. thanks larry
hand me the chainsaw, i need to trim the casing just a hair.
Replies
just curious - why not use the paralam?
well i may find out different but the price on the paralam is 575.00,last time ibought a large ibeam was awhile back but i.m thinking i could buy a used beam for 1/2 that.hand me the chainsaw, i need to trim the casing just a hair.
The advantage of the paralam is that you can easily attach the rafters to the paralam using fabricated hangers designed for rafter attachment using joist hanger nails. If you use a steel beam, you will have to come up with a method of positively attaching the rafters to the beam and attaching the end posts to the ends of the beam before removing the cross ties.
While your at the city double checking on the loading, be sure to find out what you need to factor in for wind load. It varies by region.
Have a look here for a way to combine the strength of steel with the nailing convenience of wood:
http://betterheader.com/default.asp
-- J.S.
I am curious, does the lumber used with the betterheader shrink smaller than the plate? Does the lumber shrink or is it already dried sufficiently? Or do they make the plate slightly smaller to allow for wood drying and shrinking?
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
From the pictures it looks like the wood's a little proud of the steel. You could contact them thru their web site.
-- J.S.
OK, I thought maybe you had some experiences with using them and could comment.
Anyone here ever used them and could comment about the wood sections shrinking or not shrinking?
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
I saw an article in a trade journal about some guy using the betterheader. I thought it was the most ridiculous how to article ever written. The guy was proud to be struggling to install a heavy built up header on a remod, instead of easily installing them one piece at a time.
I'm not opposed to buying the header from better header, but in that particular case, buying it knocked down makes sense. Instead, the guy created a monstor for himself, then acted like he invented sliced bread!
blue
575!
Thats makes trusses look like a better option.
I paid $100 for 2 - 3x3x1/4 20' angles recently - steel is high.
Treat every person you meet like you will know them the rest of your life - you just might!
The moment created is 45,000ft.lbs which requires a W10x39 or a W12x40.
Disclaimer: Not an engineer blah blah blah.
you know i've beenlooking for a place to park my bobcat,with a beam like that i just need to build some ramps. larryhand me the chainsaw, i need to trim the casing just a hair.
I don't understand--you supplied the raw numbers, I converted them to a load moment and looked up beam sizes in my steel manual. That's the size you need to carry that load. I've spec'd similar size beams on lots of design jobs and they are reasonably sized. Often they get installed with a boom truck or a genie lift or two.
ok maybe i don't know nothing about nothing,oh wait thats all ready been proven!lol i don't rally understand what you mean by a 45,000 moment,is that some figure for load? and are you serious that you are saying this needs a 10wide by 39 tall i beam? thanks larryhand me the chainsaw, i need to trim the casing just a hair.
ref for beam nomenclature:
http://www.engineersedge.com/standard_material/Steel_ibeam_properties.htm
all you would really need are:
W8x18 for A36 steel
W8X10 for A513 steel
Or, off the top of my head with a 'disclaimer', just 3 ea 2x12s with a 1/2" plow steel cable over an inverted 15" kingpost at the middle and tightened with a big turnbuckle - end terminations to match.
well it's 9 in the morning ,and i've already learned something, so the rest of the day i can just coast...... thats interesting that the 2nd # is your weight. yesterday i found a used beam,i call it a h beam but anyway it stands 12" with the flanges 10" wide. steel place told me it weighed about 55lbs per foot.hows that sound to use ? sounds to me after reading here that it is a little overkill ,but not much. price on it was .20 cents a pound,looks like about 275.oo for it.thanks larryhand me the chainsaw, i need to trim the casing just a hair.
What's an "h beam "?
Archaic ingles for wideflange (WF).
A contributor over at JLC has posted a nice writeup on figuring beam size given loading. Classic structural design 101. He is using steel as examples, but you can apply it to LVS and PSLs. Worth a looksee, and worth the 6pp of paper to print it on for your files.
Edited 12/17/2006 9:14 am ET by Gene_Davis
Edited 12/17/2006 10:37 am ET by Gene_Davis
what i call a h beam is when the top and bottom flanges are extra wide. the used beam that i found is 12" high with 10" flanges. what i call a i beam would have about a 5-6" flange. thats my termanalogy,and it's worth a whole lot less than you paid for it! larryhand me the chainsaw, i need to trim the casing just a hair.
What you call an H beam is more commonly called a wide flange I beam. What you call and I beam is actually called an S section- a way to remember that is that it is more slender than a wide flange. A wide flange has flat flanges- an S section has beveled flanges like a C channel. S sections are often used for columns. Personally I prefer hollow structural steel ("box" tubing and round tubing) for columns.
About the cost- scrap steel costs are very varied from place to place. $0.20/pound for used steel in good condition is fairly reasonable around here. New stuff is selling wholesale at ~$0.60/pound. And I'd rather have $375 worth of used steel in my workshop than $375 worth of new engineered lumber- especially since you can put your chain fall hoist off the beam and make use of it that way. I did the same in my own shop and it's very handy.
i am unfamiler with the s channel term,in fact now that you tell me that i would have to say that the 10" beam i found is a s channel. i had noticed that the flanges tapered out to the edge instead of maintaining the same thickness the width of the web. not that i knew alot about steel beams but i sure have been educated with this post.around here 20-25 cents a pound is what everybody is getting for there used stuff. the 12" that i found is 25 a pound and its 25' long so not much waste.chart says it should weigh about 53-60lbs a foot,should come in at 375. or so.i think i'll get down there after xmas and pick it up. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
http://www.efunda.com/math/areas/RolledSteelBeamsS.cfm
This site gives a table where you can get the properties of various sizes of S sections (slender I beams), wide flanges, channels etc.
You should be able to measure the dimensions of your piece of steel and figure out which section it is. Once you know, Junkhound can do the calc for you if he's so inclined and let you know an approximate load limit for your chain fall hoist etc.
with that table i nailed down the weight of the beams,think i'll stick with the 12x53 beam.they are all to heavy to lift in place so i might as well go a little extra and be able to use the hoist if i want to. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
An H beam has a flange width and beam depth which are approximately the same. A WF beam can have the flange width very different from the beam depth.
"What's an "h beam "?"
An "I" beam that's fallen over.
(-:
Q: What do you call a musician without a girlfriend?
A: Homeless.
An "I" beam that's fallen over
<g> Needs a "life alert" beeper, obviously . . .
Hmm, more than a tad 'cheeky' to use "fallen over" in a structural thread, n'est ces pas?Occupational hazard of my occupation not being around (sorry Bubba)
There's always a clown... :-)
Actually I was afraid I was going to be told for a fourth time what an H beam is :-)
Here's a place to download the "Residential Steel Beam and Column Load/Span Table"
http://www.toolbase.biz/Design-Construction-Guides/Exterior-Walls/steel-beam-column-load
This link lists the dimentions of all things steel, but this particular page is for wide flange I beams:
http://www.metalreference.com/19%20HR%20Beam,%20W%20shapes.htm
Beer was created so carpenters wouldn't rule the world.
great site,i'm going to print that off and go measuring beams,see what i can find.thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Wow! What a link!
Architectural Metal Samples Home PageSamT
Now if I could just remember that I am a businessman with a hammer and not a craftsman with a business....."anonymous". . .segundo <!----><!---->
junkhound, well i've been out beating the bushes for a ibeam.in your post you said a 8x18 would be suffient. heres what iv'e found. one 10" ,4 5/8 flange figures out to weigh about 25lbs a foot, cost is 200.00. second one is a 12" tall 10" flange 53lbs a foot cost on it will be 375.00. as always one thing leads to another ,i got to thinking,if i got a ibeam i could hang a hoist from it to unload crap out of trailer.max would be 750lbs. now does that really screw with things or would either one of these work. i don't mind spending the extra money if it allows me to do this. now you know why i go by over budget,lol thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Put in the 12 inch beam.
You can hang about an extra metric ton (2200#) from the middle of it with no problem. A little more if there is not a foot of snow on the roof to start with. .
Take a look at HF for some low cost ($100) electric overhead winches, hang one off a flange wheel trolley from the bottom of that beam and you'll be the envy of the neighborhood - very handy - you can probably even rig up the winch to start with to help get the beam in place.
Or, to put in simpler terms, W10x39 means a beam that is 10" tall and weighs 39 pounds per linear foot.
The moment created is 45,000ft.lbs which requires a W10x39 or a W12x40.
Disclaimer: Not an engineer blah blah blah.
Ya sure do need the disclaimer with numbers like that.
You're right. I forgot a step in figuring the moment. The beam size sounded right because the beams I've sized always have significant snow load or live load. Oh well, get what you pay for. Thus the disclaimer.
BTW, I do have a degree in engineering, but work as a designer and carpenter. Guess I should stick with that!
Think of it this way. Each rafter bears on the structural ridge at the top, and on the wallplate at the bottom, and the loads transferred down at each end are equal.
Therefore your ridge is carrying half of your total roof load. The walls carry the rest.
Using your loading of 25 psf, and the tributary area (that is a whole 'nuther topic) of 12 w x 24 l, your ridge beam is carrying 7,200 lbs, or a uniform loading of 7200/24 = 300 lbs per foot.
You can go right to the TrusJoist (now called I-Level) site and find out the size of their Parallam or Microlam will handle this. I'll go there now. Since you said 25 psf, I am presuming that is a snow loading plus your dead loading.
. . . . . . . . .
OK, I'm back. Took me a couple minutes.
You need either a two-ply LVL, sized 3.5 x 16 (that's two 1.75 boards) or a one-piece Parallam at 2-11/16 x 18. If your total loading (LL + DL) is greater than 25 psf, we'll need to go back to the tables.
Now, why didn't you just order trusses?
this garage is a cheaply built garage thats only 4 years old,was here when i bought the place.i posted last week about raising the rafter ties and everybody freaked out at how it was built and suggested i stregthen it up a little. so this is the direction i'm leaning now. thanks for taking the time out to run the #'s for me. larryhand me the chainsaw, i need to trim the casing just a hair.
I read the other thread. By adding a ridge beam you will be able to raise the ceiling joists, but you still have the issue of the significantly undersized 2x4 rafters. And, I assume you have to figure the additional load from the ridge beam on the header over the big garage door. Swapping that out aught to be fun. Almost as fun as sliding a 1000# steel beam under the existing ridge board - if that is what you are planning on doing... And, if you sister up the rafters too, more fun getting the new ones in place too. And for what? To save 24 sheets of sheathing and 6 squares of shingles? Looks to me like by modifying this roof you will essentially be putting some Grey Poupon and garnish on a sh!t sandwich. So in the end you will still have a sandwich that tastes like sh!t. Bon appetit!!!
Either that, or get rid of the poorly constructed roof, and install trusses or a correctly built stick built roof structure, and have a nice day. Probably take about 1/2 the time too...
mark i'm not in complete disagreement with you,if this was a house or some nicely built shop,i think your right,but as you put it this isn't prime rib,it's a cheaply built garage with vinyl siding-bolgona sandwhich. your right in that whatever i put up there will go up against the present 2x8 ridge board,so i don't have to struggle with attaching the rafters. the header across the 16' door i would leave,then stack a triple 2x12 on the top of that [i already have them]so no real tearout on header. as far as time factor goes with a fork lift i can put the beam in place quicker than i can tear off the roof,and can do the inside framing during the winter. if i was to tear off the roof i would have to wait till spring now. so what i have is a balogna sandwhich,with mustard,still just a crappy sandwich,but with some flavor.lol larryhand me the chainsaw, i need to trim the casing just a hair.
This may have already been caught by now, but I doubt you load should be figured as 25#/ft
because typical dead load is normally 15# and minimal live loaad is typically 15# in southern climates, ranging to more like 40 in average locations and way beyond that in mountain high snow areas.
I'm thinking you ment 25# live load so add the 15# dead load to that
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This is the most civil and informative discussion on structure I can remember on this discussion board. Is it because its close to Christmas?
They tell me diamonds are found in mud
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I have mud for sale, that may or may not contain diamonds. :-)
Hope you had a good Christmas and new year!
Beer was created so carpenters wouldn't rule the world.
here's Mud in your eye!;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!