truss connection
truss connection
(OP)
the steel fabricator wants to use the attached detail for the gusset plate connections of a large truss. The web member loads range in magnitude from 60K to 550K, and the chord forces max out at 1700K. Something about this set up has me worried and wanted to see others thoughts on this. The chord flanges are 1.75" thick as well, and they are coming up with 1/2" gussets to full pen weld to them. Assuming they design it properly, taking into account offsets of the connection from the work point, are there other concerns for this connection? My gut says no to this, but maybe I am over-reacting.






RE: truss connection
Mike McCann, PE, SE (WA)
RE: truss connection
as with mike, overlap the gusset and the chord flange, outer face is more obvious, but the inner works if they want a flush outside; use packers if needed. some more bolts would be a nice touch.
Quando Omni Flunkus Moritati
RE: truss connection
A sketch of the truss and its supports might help.
BA
RE: truss connection
1) Member fit up as BA mentioned.
2) I'd think that it would be difficult to align the gusset plates to be nearly vertical.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: truss connection
From the AISC website:
For people who need technical assistance, innovative solutions, or tools to make structural steel design even easier, the Steel Solutions Center is your #1 source of information for structural steel.
Contact the Steel Solutions Center at 866.ASK.AISC
or solutions@aisc.org
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: truss connection
RE: truss connection
RE: truss connection
Also, how did you expect them to fabricate the truss/connection? I would have expected the connection to have plates that covered the flanges of the chord, similar to those indicated by msquared. Is that what is shown on your drawings?
RE: truss connection
Caution: Avoid welding on jumbo sections in tension to avoid lamellar tearing. I cannot remember the (Jumbo sections) Group Number, since I am retired and gave away all my books.
RE: truss connection
RE: truss connection
@ Jike: Can you elaborate upon your jumbo section lamellar tearing comment? I've not heard of that before. Beyond a certain thickness of material, does cross grain tearing become an issue in all directions?
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: truss connection
The moment would be generated from the free body diagram of the gusset - at least in a 2 web member configuration, at the interface of the gusset to the flange there is a moment since that plane is offset from the work point. At least that's what I see when I look at it kinda like the uniform force method. I am not well versed in that, so maybe I am looking at it wrong.
jike - is there a reference you have for the lamellar tearing?
RE: truss connection
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: truss connection
The issue with Lamellar tearing is with the weld detail and if you create constraint in the weld.
The AISC manual has some examples of bad details (see section on welds - Part 8 in the Thirteenth Edition).
Your detail is a plate end to plate end detail so this shouldn't be an issue.
Also - it is usually only an issue with plate thicknesses larger than perhaps 1 1/4".
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: truss connection
The two diagonals could be shop welded instead of field bolted. If it is a parallel chord truss, the vertical member carries no load and could either be omitted or attached with nominal bolting.
The bottom chord splice must be designed for 1700K tension and is best located to miss web members.
BA
RE: truss connection
I don’t know what size the top chord is, but the flanges look pretty thick. Punching or drilling holes through it might be difficult.
And as has been mentioned, the fit-up challenges are the same if the gusset is welded as shown or if it’s connected across the flanges of the top chord.