Yield Line Mechanism of a Flush End-Plate moment connection. 2

[Mikce]

I'm sorry for my bad English.
I'm working in Vietnam and I'm familiar with TCVN (Vietnamese standards). When it comes to flush end-plate moment connection, TCVN doesn't have any formulas to calculate the end plate thickness.
We are involving in a project with a foreign client, they utilize the AISC 360 standard. I've read this document for a while, but I can't get the hang of it(especially the Yield line method).
I'm designing a flush end-plate moment connection from I-beam to I-beam by 16 bolts (as images I attached). I've had read the AISC Design guide 16 as well, but I can't understand the formula for calculation of Yield line. This flush end plate connection is sustained only to a moment of 450 kNm in value.
I assume the neutral axis would separate the plate into 2 equal regions, compressive region, and tensile region.
Could anyone tell me how to deduce the formula for yield line pattern of this case, please?
I just wanna check whether the end plate has adequate thickness according to AISC 360 (I design the connection according to TCVN, current end plate thickness is 12 millimeters).

Thank you so much, I profoundly appreciate your help!

 

[Mikce]

https://files.engineering.com/getfi...-c61c-4534-a97c-78209eefdac6&file=Capture.PNG

 

[JoshPlumSE]

I believe you mean the AISC 360 standard.

Compression side:
There is not compression yield line for the compression side. The theory is that on the compression side, the beam flange pushes directly against the plate which pushes directly against the column flange. So, the end plate bolts don't participate (except to resist vertical beam shear).

Tension side:
The tension flange force gets into the plate (through the weld), then it has to transfer from the plate to the bolts. That's where the yield line concepts come into play. In your case, I would ignore the bolts closes to the mid-depth of the member (between the two stiffeners) and of course ignore (for yield line) the bolts on the compression side. That would mean that you've got a 6 bolt flush stiffened end plate. This arrangement isn't given in any of the literature that I know of. Though you could probably derive it if you wanted to.

That's reasonably close to the the formula for 4 bolt flush stiffened end plate given in table 3-5 of the design guide. Conservatively you could use the design guide formula and ignore the h3 bolts. You could also look up some of the reference papers (Sumner and Murray) cited in the design guide to get a better idea about how to derive the formula.

 

[Mikce]

Yes, I mean AISC 360, my bad though.
Thanks for your kindness, JoshPlum.

 

[BAretired]

I assume the neutral axis would separate the plate into 2 equal regions, compressive region, and tensile region.

I'm not so sure about that assumption. I don't have the properties of an I-Beam designation I-1200x250x8x12 but I'm guessing it's a Welded Wide Flange with a depth of 1200mm, flange width of 250mm, web thickness of 8mm and flange thickness of 12mm.

450 kN-m is a small moment for such a large section, so it may be conservative to assume the N.A. in the middle, but I think it would tend to shift toward the compression side of the beam which means that more of the bolts, probably all of the bolts would be in tension as the beam rotates around the compression flange.

BA

 

[Istructeuk]

May I ask whether this beam is a part of a moment-frame or a braced-frame?

 

[Mikce]

I'm not so sure about that assumption. I don't have the properties of an I-Beam designation I-1200x250x8x12 but I'm guessing it's a Welded Wide Flange with a depth of 1200mm, flange width of 250mm, web thickness of 8mm and flange thickness of 12mm.

450 kN-m is a small moment for such a large section, so it may be conservative to assume the N.A. in the middle, but I think it would tend to shift toward the compression side of the beam which means that more of the bolts, probably all of the bolts would be in tension as the beam rotates around the compression flange.

Sorry for my late responding.
Yes BAretired, it is a Welded Wide Flange with a depth of 1200mm, flange width of 250mm, web thickness of 8mm and flange thickness of 12mm.
Initially, I have the same idea with you, I assume all the bolts (except for bolts in compressive region) would be in tension. The N.A is above the compressive region (1:6 - 1:7)h1.
AISC also mentions about this case, but the formulas are used for moment connection between I-beam and column. As the connection is sustained only to moment, we can calculate the equivalent moment in end plate, then we can deduce the end plate thickness (using theory of Krishnamurthy, Hendrick and Murray).

 

[Mikce]

May I ask whether this beam is a part of a moment-frame or a braced-frame?

It is a part of a moment-frame, Istructeuk.

 

[Istructeuk]

By saying this beam is a part of a moment-frame I’m assuming it is a multi-storey moment frame rather than a PEMB single-storey portal frame.

If so, saving thickness of end plate isn’t a good idea because Type 1 FR (Thick end plate, smaller diameter) is always suggested and preferred, so 12mm thk. endplate doesn’t seem good enough for 1200mm deep beam. You may also consider welding design of 60% of section capacity in both moment and shear instead of 450kNm. Besides, is it allowed any slippage? AISC does not require preloaded bolts for end plate connection but consider the whole frame behaviour (load reversal, vibration, seismic…), preloaded-bolts may be required in some cases.

Last but not least, if the beam splice location isn’t close to any out-of-plane retrained points, P-Delta effect would be investigated for this beam since it is a part of a moment-frame.

However, for PEMB, you may ignore the notes above because it is generally relaxed in term of strength, stiffness and continuity requirements.

Cheers,