Wide Flange Beam (forces on web)

[ringerA]

Where do I start? I have a wide flange beam with a rectangular cut out in the center of the web. I am putting a jacking cylinder inside the cut out that will push the beam apart longitudinally. I just need some generic calculations to find the Su under a predetermined load.

Note: the beam is plenty long so longitudinally there is plenty of meat on both sides of the cut out.

 

[J1D]

Give more detail of cut-out dimension, size of the beam and loading. Modeling a 3-D wide flange beam with plate elements may help you find out local stress. In addition, there should be some maximum web cut-out limit.

 

[ringerA]

The beam is a W36x300x15'-0"
flanges = 1.25"x16.5"
web = .75"
flange to flange(inside) = 33.625"
beam = 15'
Cut Out = 16"x9'-0"

Loading is a unique case. A 400TON jacking cylinder will be placed in the cut out and will basically be pushing the beam apart as it extends longitudinally. I really just need a quick generic way to find out if the beam will support the load. I am really just concerned with how the beam itself will act. The ends of the cut out will be thoroughly reinforced.

 

[VirtualEngineer]

You could calculate the section properties of the left over "T" sections. Treat them as beams with fixed ends.

I dont think they will take 400 tons without failing.

Regards,

JPJ

 

[VirtualEngineer]

I just noticed that you said the forces are along the longituinal axis of the beam.

The two "T" Sections will probably fail in tension.

Regards,

JPJ

 

[rday]

Well

Quick calc.

neglect remaing web for simplicity
assume beam loaded through centroid

Total flange area of W36x300 = 55.96 sq in
Tension force = 400Tx2000lb/T = 800,000 lb

Axial stress=Tension force/flange area = 14,296 psi

assume the W shape conforms to ASTM A529 grade 42

Minimum Yield Stress = 42,000 psi
Ultimate Tensile Stress = 60,000 psi

You decide if the shape will support the load.

However, I think the webs (even reinforced) will cripple and fail before the flanges fail in tension. Of course the reinforcing is an unknown to me.

Rik

 

[dozer]

ringerA,

Just out of curiosity, what is this for? BTW, I agree with rday. Do you have access to a FEA program? If not, you could check web crippling/yielding using section K (I think, I'm at home and don't have it handy) of the AISC Manual of Steel Construction, 9th ed. That's the ASD edition, there's also a LRFD edition.

 

[J1D]

RingerA

I guess the wide flange is to be used as a loading frame(?) This web opening is extra long, but fortunately it is not used as a beam.

The calculation shows the total uniform stress is not bad (as rday calculated, but the total remaining sectional area is only 54.46 sq.in based on dimensions given by you. Futher, if the beam is designated as W36x300, according to AISC, the flange thickness is 1.68", web thickness is 0.945", which give a total remaining area of 72.368 sq.in). However, you need to consider web crippling and local stress concentration, etc. One of the approaches to help local high stress at the corners is to weld horizontal reinforcing bars at top and bottom along the opening, particular at the corners

 

[ringerA]

Thanks alot for the help guys.
Dozer,
The beam is going to be used to test two 400Ton hydraulic jacking cylinders. They will be stacked and while one extends the other will retract. We have several of these that have been sitting for a few years and we had to come up with a way to test them before we sent them out to field.
P.S. I don't have any FEA software but I wish I did.

 

[kkoloj]

AISC has a series of informative short "design guides" called STEEL NOTES or something like that. One of the "design guides" deals with both square and circular openings in wide flange beams. Basically there are a series of equations and charts to use to determine if the net section will work for a given loading. It it does not work then, as J1D mentioned, you can weld horizontal plates at the top and bottom of the opening (this "fix" is also addressed in the STEEL NOTES).

I have used them, but it has been a while. If you can't find it, let me know.

 

[rday]

Am I reading the problem wrong?

I am thinking the W-shape will be loaded axially in tension from within the cutout (see ringerA's second post).

If this is the case, I don't think AISC's Design Guide 2 (the one kkoloj refers to) will help much. I think it is intended for shapes loaded as beams not columns. But I would have to check.

Also, in this case horizontal (aligned with flanges) reinforcing wouldn't seem to have much effect as your not looking to increase the section modulus around the opening to resist bending.

I still think the webs will be the failure point.

So are you testing the cylinders? Let us know how it goes.

Rik

 

[LPPE]

Maybe I'm reading the problem wrong, but sounds to me like you're cutting out the web of a piece of W36x300. Then, placing a 100 ton jack in the opening to test the jack.

If thats the case, I would look at the remaining piece of web and flange as a T with the web in compression. My guess is that it would buckle under 100 ton load, and you'll be left with a warped useless piece of W36.

If you draw the remaining T section in ACAD, you can get section properties that way also.

 

[ghghghgh]

I think you would want to weld a longitudinal stiffener to the web at mid height on both sides of the web and cut out to ensure buckling does not occur. Then, from the above calcs, it looks like the section could develop the force to test your jack.