Bevel cutting W-section steel beam at support 1

[Montreal.eng.]

Hello, I have a customer that is asking if it's possible to bevel cut a steel beam in order for them to recess a W8x31 beam into their attic. In my opinion if the cut doesn't go beyond the support width it doesn't weaken the beam in shear nor in bearing. The load on the beam isn't immense, It carries some of the roof and attic load, the steel beam and columns was at the request of the client that works for a steel company.

I just want to make sure that I'm analysing this correctly.
Also, since the top of the beam will be popping into the attic, I will have to ensure top lateral bracing at supports. Do you guys have any efficient way to do this? Is a

The sketches below are written in french (If the name isn't obvious enough I'm from Montreal, Quebec)
Poutre = beam
colonne = column
Solive - Joist
Toit = Roof

Thank you in advance,

 

[KootK]

I'm not saying your wrong, I've just never thought of it this way before.

I could be wrong. It happens at least quarterly according to my records.

What if the same beam/column setup, but a single beam framing in at the center? What if the same setup, but a single beam framing in 2.5' from one end only? Now I'm not so sure.

I do love me a good thought experiment ala Einstein. Lab work is for the weak minded.

First off, the whole setup could be prone to a rigid body rotation about a vertical axis passing through that one beam. We'll assume that's dealt with.

Secondly, I still contend that we're in compliance with J.7 BUT we are duty bound to check the two half spans as cantilevers effectively. What is a no brainer for rotational restraint at 4' oc becomes worth of more study when it's a single point of rotational restraint.

 

[KootK]

I'd check the beam as a coped beam (3" cope, 7" length) to get the approximate capacity at the end.

That's clever. I can't think of anything better.

 

[KootK]

This is something that I'd forgotten about. Unframed beam full depth stiffeners are actually full web depth stiffeners. Which basically makes them partial depth in the sense that I've been thinking of them.

The more that I read this paragraph, the more tham I'm starting to see it the other way. It's like the panda that eats, shoots, and leaves... and then gets incarcerated.

Full-depth stiffeners are required at the unframed ends of beams and girders where those beam and girder ends are not otherwise restrained to avoid twisting about their longitudinal axis.

Viewed like that, I think that I'm coming around.

 

[phamENG]

I'm guessing that's from 360-16? I really do need to buy the new book.

 

[KootK]

It is indeed from 360-16. I gather that some combination of fiscal restraint and morality regarding intellectual property prevents you from having a copy of the new book. Even if you don't have a copy of the good book, surely you've got the commandments which are freely available: Link

 

[canwesteng]

I could have sworn there used to be some way to assess these unstiffened ends in the commentary of 360 before but I might be losing it. In any case I think to default to always using stiffeners at unframed ends is overkill, since there is certainly some rotational restraint without them.

 

[WinelandV]

canwesteng,

I checked my 13th edition commentary, and it only has the first sentence of the paragraph that KootK posted. If there was a procedure, it must be in something pre-2005.

 

[KootK]

I could have sworn there used to be some way to assess these unstiffened ends in the commentary of 360 before but I might be losing it.

I believe that procedure to be the sideway buckling check. WArose and I have had a least two intense discussions on this topic and that is, in large measure, what informs my current thinking. I was only able to dig up one of those threads quickly: Link

 

[KootK]

Back to the forensic potential, this collapse in British Columbia was essentially caused by the lack of stiffeners over a column facilitating a side-sway buckling failure in a OWSJ system. I'm certainly in favor of including stiffeners which would serve as cheap insurance in the many situations in which it makes sense to do so. While I do believe that one can calc their way out of stiffeners in many cases, I also feel that it's usually not worth the trouble / uncertainty design side.

 

[WinelandV]

KootK, if that is the case (that you can check assess the unstiffened end via J10.4), why not just write J10.7 to say

"At the unframed end of beams, check sidesway web buckling. Use full web-depth stiffeners if req'd."

I'm not saying you're wrong, just that it seems odd to include J10.7 if you can just check the end using J10.4.

 

[KootK]

I see your point, of course. However, in my travels, I've encountered several instances in which codes / standard provisions have been ambiguous and/or poorly coordinated internally. Heck, I remember an issue coming up here once where we reached out to AISC and it turned out that AISC itself didn't really understand the origins of a provision because the one guy that spearheaded it had died. Seriously. Here, I'm not even sure that I agree with your guys' interpretations of "unframed" or "restrained against twisting about a longitudinal axis". You've shifted my needle some but, with that kind of uncertainty in play, I'm hesitant to read too much into semantics.

 

[TLHS]

Back to the forensic potential, this collapse in British Columbia was essentially caused by the lack of stiffeners over a column facilitating a side-sway buckling failure in a OWSJ system. I'm certainly in favor of including stiffeners which would serve as cheap insurance in the many situations in which it makes sense to do so. While I do believe that one can calc their way out of stiffeners in many cases, I also feel that it's usually not worth the trouble / uncertainty design side.

I've got to dig through my miscellaneous papers and track down the partial insurance investigation file I have that relates to some of this. I have a connection to an engineer who worked on that side of things and I ended up with it at one point. It's been so long since I looked at it, that I don't even remember if there was anything interesting in it.