AISC Section J10.2 and J10.3
AISC Section J10.2 and J10.3
(OP)
I am looking over AISC Sections J10.2 and J10.3 of the 13th edition manual. I would be using these sections to check the requirements of a column used in a beam/column moment connection. At the end of each section the AISC recommends a pair of transverse stiffeners or a doubler plate be used to increase the strength of the column web. How do you determine which is better to use, stiffeners or doubler plate?
From talking to fabricators I realize that stiffeners a a much more cost effective solution. Based upon this information, I assume that the AISC allows a doubler in the odd case that a connection does not need stiffeners but needs a doubler (so why use both). Is this correct?
From talking to fabricators I realize that stiffeners a a much more cost effective solution. Based upon this information, I assume that the AISC allows a doubler in the odd case that a connection does not need stiffeners but needs a doubler (so why use both). Is this correct?






RE: AISC Section J10.2 and J10.3
When you guys pose your questions the way you have, without attaching the few pages of AISC, Ed.13, which you are looking at, you stand a good chance of eliminating answer/comments from some of the people you might most like to hear from. It seems more and more common here on E-Tips that people ask about formula (J10-3.a.7, sub. 3.g) without even mentioning the basic subject matter, not exactly your case here. And, many people with some knowledge of the matter, may not have that Ed. 13 in hand, so they will tend not to participate. If you don't have the time to ask your question in a complete way (un-lazy way?), why should we go out and buy the book to participate? I think there have been several other thread on this general topic in the past.
In any case, it seems that you've answered your own question by talking with some fabricators. You want to get those concentrated forces into the entire member, actually distributed to both flanges through the web, without buckling its web, acting as a flat plate. And, you want to do this in the most economical way for the fabricator, as long as your analysis justifies that particular approach. There may be instances when one or the other approach is the better detail, although not the least expensive. Obviously, increasing the web thickness will reduce the likelihood of web buckling while transmitting the flange forces from the beam to the column. But, the web doubler pl. is tougher to fit and weld properly.
RE: AISC Section J10.2 and J10.3
RE: AISC Section J10.2 and J10.3
I worded the problem the way that it was to try and eliminate the people who are unfamiliar with the AISC 13th edition manual. I also don't want to photocopy/scan 5 pages out of my AISC manual as I am not a large shop and that would take some time to complete. The material also has a copyright.
Sail,
We are pretty much thinking the same thing. Stiffeners whenever possible and doubler when they are required for shear. I have thought about using a diagonal stiffener as you have suggested however, I though that would make a mess out of the weak axis shear connection so I have never bothered investigating the possibility further.
RE: AISC Section J10.2 and J10.3
RE: AISC Section J10.2 and J10.3
This is more of a bit of research for a potential project. I would need to design some connections for a fabricator. The EOR is requiring that the connection be designed for the full moment that the connection could see (column or beam strength). Changing column sizes around would not work since the column being used are W8x67's (plus this would mess around with frame stiffness). This would required a section size change which might not be architecturally acceptable.
RE: AISC Section J10.2 and J10.3
RE: AISC Section J10.2 and J10.3
Actually the system was designed using R=3.5. I don't think there is much difference in this instance between designing with R=3.5 of R=3 but I am not the EOR and I have begun to send the information up the proper channels to see if something could be done (not likely with R=3.5). FYI, this is something that is done all the time and causes many problems for fabricators. On the same job I am to design the simple beam connections for 2x the reaction I would get using the uniform load tables.
When I told the fabricator about the doublers he asked if there was any way for him to know if they were needed prior to bidding the project. I said sure, I have a spreadsheet that performs the column strength calculations for me..... however I'm not sure it is wise to include the cost of the doublers in your proposal unless you have the ear of the client or are an incredible salesman as others may not be including doublers in their proposals.
Looking back at my spreadsheet I was just wondering when to use a doubler or a stiffener. It appears as the following (as I see it anyway)
Flange Local Bending :stiffener
Web Local Yielding, Web Crippling, Web Compression Buckling: stiffener or doubler
Web Panel Zone Shear: doubler
RE: AISC Section J10.2 and J10.3
It looks like you have Ordinary Steel Moment Frames with R=3.5. Make sure you meet the detailing requirements of AISC 349 as well as the AISC 360. AISC 349 requires the connection to not just be designed for the full moment strength of the beam but 1.1*Ry*Mp, which may be significantly more (see clause 11.2a).
I'd also recommend that you check out AISC Design Guide 13 which has some examples of stiffener design.
The use of some of the other requirements you mentioned (2 times the uniform load capaicity for shear connections) indicate that the EOR may not be super familiar with current steel design practices. This may be an opportunity for you to suggest some ways to increase efficiency and save everyone some money.
RE: AISC Section J10.2 and J10.3
RE: AISC Section J10.2 and J10.3
I understand the detailing difference..... but the difference in base shear would only be 16% increase (3.5/3-1). Again, I'm not sure if the structure could qualify using R=3 but if it was switched around I don't think there would be that much difference.
RE: AISC Section J10.2 and J10.3