Crazy Connection
Crazy Connection
(OP)
Check out this crazy connection.....
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: Crazy Connection
RE: Crazy Connection
This happens A LOT.
ConnectEngr....thoughts?
RE: Crazy Connection
Toad:
What framing is this or did you randomly stumble on this? It looks like fin plates welded to a column flange and receiving the brace and beams. It appears to be braced frames in both directions and some sort of horizontal bracing diaphragm?
We are Virginia Tech
Go HOKIES
RE: Crazy Connection
RE: Crazy Connection
Power structures like these don't really have a diaphragm, just horizontal bracing (I think that is what you meant).
I'll tell you, and maybe I am just a dummy, but these connections are extremely difficult to design. It takes a lot of time and effort.
RE: Crazy Connection
We are Virginia Tech
Go HOKIES
RE: Crazy Connection
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Crazy Connection
Then comes connection time and they become hard to connect due to extremely high axial loads.
I really would like to hear what ConnectEngr has to say.
RE: Crazy Connection
Looking strictly at this joint, not knowing what else is going on, one could make the following suggestions:
The wide flange diagonals in the vertical braced frame could be turned with their web vertical, so that they could be connected with claw angles to the gusset, like how the horizontal member in this plane is connected.
The wide flange diagonal in the horizontal plane, connected with angles on the web, could be changed to a double angle member (or four angle), although it might be hard to achieve the required member capacity this way.
RE: Crazy Connection
Hell, with a little finesse, there is room for another 6 or 8 members to frame into that joint. CAD and FEA can do anything and everything. If you chase those loads, forces and reactions around enough, you finally lose them and can forget about them.
RE: Crazy Connection
Is that some sarcasm I sense?
Reminds me...My father used to say to his sales guys "if you chase the job long enough, you're going to catch it".
I know sometimes these connections are a necessary monster....but I have been forced into them a few times because along with our design assignments we were handed mill rolling schedules so as to say "here you go, these are the beam sizes you can use this week".
RE: Crazy Connection
We designed similar connections for a cement plant in Costa Rica, with every beam moment connected and braced vertically and horizontally. 4 moment connections and 16 brace connections at each column grid. Initially they were field welding everything. They had a beam line, but did not trust it's accuracy. Due to obvious construction delays, we were called. We convinced them to trust their beam line equipment, and introduced them to Ken Lohr and tension control bolts. The remaining 5 1/2 stories were completed faster than the first 1 1/2.
Thanks for the picture TJ. I love this stuff. I wish they all looked so fun.
More examples:
h
http://www.FerrellEngineering.com
RE: Crazy Connection
You are correct with the beam sizing. There is very little shear, so the beams a simply axial loaded struts. Beam end rotation is not an issue. But the beams are generally "column size" in depth and weight.
http://www.FerrellEngineering.com
RE: Crazy Connection
How does one handle design of a lateral system with moment connections and bracing combined? Is the bracing there for secondary forces?
IMHO, the design of these connections is very trying to say the least. Until one embarks on such a design he may not understand just how difficult it can be.
Then again, I may just be a dummy
RE: Crazy Connection
http://www.FerrellEngineering.com
RE: Crazy Connection
RE: Crazy Connection
Hg
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RE: Crazy Connection
Let the software do all the thinking. Why should an overworked and underpaid engineer, second guess a computer. "If it wasn't practical, the software wouldn't allow it". Go ahead, it wouldn't be call "optimized" if the sizes weren't the best choice. Nucor makes all those different sizes for a reason. Print out the fancy analysis, load case combinations, and the cool 3D renderings. Make um all fixed and braced. Show the envelope forces on the contract drawings. And close your eyes...
This is just more work for me. I am confident that in most cases I can design a connection for the forces and interactions. BUT, there is no guarantee that anyone will be able to afford the design, fabrication, and erection costs.
by the way...
I don't think your picture represents this type of thinking. We frequently see those connections in industrial framing with axial forces (no moments) and an open channel to the designer to discuss all options.
http://www.FerrellEngineering.com
RE: Crazy Connection
RE: Crazy Connection
I don't know if the printouts can now show the forces for the individual load cases, diagrammatically, but I bet the detailers would like it if you sent then .
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Crazy Connection
RE: Crazy Connection
I started on the drawing board as well. For most structural steel detailers the force combinations might cause more harm than good. Regretfully many detailers are facing the same computer transformation. They don't use calculators to determine angles and detail geometry. They must lay them out to scale in CAD or model them. They are rarely even taught engineering vocabulary. An even less about statics or basic engineering design. Force tables are not very helpful without a basic understanding of shear, moment , and torsion.
This said, detailing has come a long way since I had to practice with letterguides and rolling pencil.
RE: Crazy Connection
And thanks for the picture.
http://www.FerrellEngineering.com
RE: Crazy Connection
RE: Crazy Connection
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Crazy Connection
RE: Crazy Connection
I have a suspicion that the out-of-proportion number of bolts may be because of seismic detailing requirements (again, I defer to Connect here, hi-jack as required, I never really asked a question this post anyway). Same might be true for all the doubler plates.
My only complaint(from past dealings with these things) is some of the problems can be mitigated in these connections by simply choosing a different beam size. On a much simpler level, there has been times when I was doing powerhouse work (not working like a powerhouse) where I would be tasked to design connections for another engineers framing. There would be times when a simple pair of clip angles would suffice for a lightly loaded strut (pure axial) and the design engineer would have something like a heavy W10 or W12. My standard clips (3/8", 1/2", 5/8", 3/4" thick) wouldn't work on a beam of that depth but might have worked on W14. Again, just a simple example.
When I design my own steel and connections I try to use a little foresight; is this beam going to be easy to connect. Member design is mush simpler and less time consuming than connection design.
RE: Crazy Connection
Often these connections are more like a puzzle. Tracing the forces and where the components are taken, the eccentricities, and how will it be erected. This is art.
http://www.FerrellEngineering.com
RE: Crazy Connection
RE: Crazy Connection
You are referring to progressive collapse and "tie forces". This will be a requirement for many structures with the next IBC. New York adopted this requirement almost immediately after 9/11. We provided the connections for Building 7, the one that was allowed to burn until it collapsed. And one of the first rebuilt. The design requirements have been refined, but for Building 7 every beam to column was designed for a minimum axial load of 150kips.
http://www.FerrellEngineering.com
RE: Crazy Connection
By next IBC do you mean 2012?
Thanks for the warning.
RE: Crazy Connection
http://www.FerrellEngineering.com