8 inch I-beam - how much will it hold?

One of the projects involves both re-doing the garage and lifting a ford 4-cyl motor out of a car. There's a fellow selling an I-beam locally, 13
feet long, 8 inches deep, 4 inches wide (no web thickness specified). This would span the garage nicely - could I rely on it to not bend if I hook up a hoist to the centre and lift that motor? Supported on the ends only...
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thickness
to
I don't have my blue manual handy, but unless that thing is a brake- formed sheet metal beam, it'll probably handle the car, engine and all. In that size, it's gotta run at least 11-lb per foot.
Your assignment is to get the beam mounted in such a way so that it cannot twist _at_all_ when loaded. Probably the best way to do that is to weld the ends to some substantially larger mounting plates onto which A-frame legs would attach.
Get a trolley for that size beam, and you'd have a nice gantry crane.
LLoyd
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On Wed, 18 Mar 2009 07:32:24 -0500, Lloyd E. Sponenburgh wrote:

My father once arrived at a house fire driving the fire truck. The house was located across a stream from the road, with an obviously owner-built bridge between him and the house. So he set his right-seat guy out to take a look to see if the bridge was sturdy enough.
"Wow! It's got 12 inch I-beams under there!"
Well, that's gotta be stout enough for ten fire trucks, right? So off he goes, and in the middle of the stream the bridge sags badly. It's still passable, but it's obviously ruined.
After the fire he goes and looks at the bridge. There are the 12" I- beams -- on their sides, by design.
--
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There's one born every minute, Tim Paul
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...
I have this exact beam in my garage. I have a trolley for it with a one ton hand "rolling chain" hoist. Very handy.
Karl
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On Wed, 18 Mar 2009 11:57:21 GMT, _

There are at least 3 standard wide-flange beams that fit that description, running from 10 to 15 pounds per foot. It'd be irresponsible to make a firm recommendation based on incomplete information, but I think it's unlikely you'd have any problems lifting a 4 cylinder engine with a W8x10 (the lightest of the standards) wide flange beam spanning 13 feet as long as you use a little common sense.
--
Ned Simmons

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On Wed, 18 Mar 2009 11:57:21 +0000, _ wrote:

There are engineering tables for that sort of thing. I don't know where the right place to look is, but that's all been reduced to "look it up and run a couple of numbers".
As Lloyd pointed out, mount that sucker so it absolutely positively cannot turn on it's side or fall off of it's supports.
--
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wrote:

The tables are in the AISC Steel Construction Manual, but first you need to know which table or chart to use and how to apply it appropriately. There's lots of jargon and abbreviations in the data that the user needs to interpret and then determine whether any of it is relevant to the case at hand.
For example, the charts and tables assume a factor of safety for structural applications which is much lower than the practice for overhead lifting.

That's a good start. <g>
--
Ned Simmons

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Ned: Baumeister and Marks Standard Handbook for Mechanical Engineer that I have just about ground into unreadable by repeated usage, and I'm not a mechanical engineer, has a table 2 on page 5-32 that shows a simply supported beam which means the ends are only restricted vertically and not welded into a vertical column max deflection is:
f (W* (5* L^3))/(384* E*I) W= weight applied to center of beam in pounds L= length in inches E= 29* 10^6 if it is steel I = the moment of inertia of the I beam section. Note the way to calculate this is found on page 5-38 of the same book. The drawing is a bit messy but the I factor does depend on the web thickness. It is a no brainer if you have the picture from page 5-38 and all the dimensions from the I- beam
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On Wed, 18 Mar 2009 18:25:43 -0700, Stuart Fields wrote:

f
The moment of inertia may depend on web thickness, but you'll find it doesn't depend _much_ on web thickness.
--
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wrote:

And that's a perfect example of the hazards of putting too much faith in handbook tables. Look beyond Table 2 and you'll see a section "Maximum Safe Load on Steel Beams." It deals with load reductions for beams without lateral bracing, which is quite likely what the OP has in mind. That's also one of the factors I alluded to that's in the AISC charts, and it's easy to miss there as well unless you know to look for it.
BTW, the deflection formula you gave is for a uniformly distributed load, not a concentrated load like a hoist at the middle of a span would apply. And in any case, the deflection isn't going to tell you whether the beam is adequate to support a given load.
Was it Rumsfeld who said it's the stuff you don't know you don't know that's the most worrisome?
--
Ned Simmons

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Oops! Ned you are right. I grabbed the wrong beam condition. BTW I designed a sail boat trailer for a full keel sail boat using the deflections as the limiting condition for obvious reasons. Also a spiral staircase, a hydraulic engine hoist and a building addition, and a helicopter trailer modification. As well as the deflection calcs for a 30' non standard I beam with both distributed and concentrated loads. All had some safety factors added and all have been in use for some time with no failures to perform. With all that said, the table 4 on page 5-35 does have an easier to use formula for safe loads. Given that the ends of the I beam are restricted from rolling or departing from their location, I fail to see that using deflection, and keeping it small, doesn't yield a safe condition. This technique was used on the building addition, as well as the 30' non standard I beam with the concurrance of a P.E.
Stu Fields
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Well, I certainly hope you don't build things that I have to use with your methods. I ran some calcs on standard 12" A36 steel I beams. Using the published yield strength (the point where it bends and takes a set) http://www.matweb.com/index.aspx search on A36
of 36,000 psi, I can get deflections in the 1/240 range. This is the equivalent of NO factor of safety.
These calcs assume multiple beams that are cross braced and do not include any derating to account for mid space twisting

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wrote:

Is that titled "Approximate Safe Loads in Pounds on Steel Beams?" (I'm looking at the 5th edition, which I suspect is older than yours.) Note that this is an approximation, and uses a very conservative value for allowable stress. It'd be interesting to compare results from that table to the AISC code.

Here's an example: Take the OP's 8" beam (let's assume it's a W8x13) and set it up as a simply supported beam 5 feet long and apply a 12 ton point load at the middle. It'll deflect .090", which is less than 1/600 of the span, but the stress in the flanges will be over the yield of A36 steel, and about 1.6 times the allowable stress.
Make the beam even shorter and you'll get to a point where shear rather than bending stress is the limitation on loading.

Quite often deflection *is* the controlling factor. Presumably your PE evaluated the design and signed off on your deflection calculations as appropriate in that instance. He might not have agreed if the beam was unbraced or being used for overhead hoisting.
--
Ned Simmons

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Rule of thumb is that for wood beams you do the deflection calc first, then the strength calc since wood has a relatively low modulus of elasticity. Steel is the opposite, you figure the strength first since that is likely the limiting factor.

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I could be wrong but are rule of thumb in my head is a beam should only deflect 1" over 360" of lenght.
Made up beams must be constrained so they don't twist.
Stay inside that, life is good if I didn't blow it.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
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That rule is for beams supporting sheetrock walls, so they don't crack. More deflection is allowed otherwise.
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Wes wrote:

My shop / hangar was made with 4" square pipe posts and 10" purlin thirty feet long - unsupported. But I never hung much weight from them.
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them.
Some time, look up the dead/live load capabilities of a 3-1/2" x 12" lam-beam. You'd be amazed.
Consider, they use them to span garage door openings (supporting roof structures) up to 22'.
LLoyd
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On Wed, 18 Mar 2009 19:49:44 -0500, Lloyd E. Sponenburgh wrote:

The I-beam is $75.
I know sort-of about the laminated beams; put a pair of 'em in the kitchen where someone had taken out a wall 40 years ago. The single 2x10 they put in had sagged about 2" in the middle...didn't help that on one end it was notched to about 3" height to sit on the top plate - not a stud; and one the other about 1/2 inch was on a stud, that was all.
When I saw the state it was in one of the first things I did was tell the teenager not to do any jumping on the floor in the room above - not that he had, but he's a teenager, they're unpredictable.
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