HSS WALL PLASTIFICATION! 4

[Ben29]

I am doing a connection design for a fabricator. The beam has an axial load of 110K on each side of a column. Fabricator wants to use a shear plate connection. The shear plate connection is failing... the limit state is HSS Wall Plastification. My question is: Can I add a plate below the beam (weld to column and beam flange) in order to help transfer the axial load along a wider area? See image below. Thanks in advance.

 

[jayrod12]

What about using a WT as your shear tab instead of just a plate? Then the WT flange would contribute to the resistance.

 

[SteelPE]

Why not do a thru plate (FYI 110k is quite large, so I am not even sure that would work)?

what is the shear on the end of the connection?

 

[sbisteel]

Slot the HSS and provide a thru plate, assuming the load does not need to go into the column.

 

[dik]

Are the bolts through the wall of the HSS? or are they behind and in the foreground? 10 bolts total ea side? Both suggestions of a ST and a through plate for 110K loading seem appropriate... and I would be looking at either solution.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dauwerda]

I like the through plate idea as it sounds/looks like the load needs to transfer through the column from one beam to the other, not get resisted by the column. The thing to check then would be buckling of the through plate when in compression.

 

[dik]

load not go into the column???

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Ben29]

The shear on the W24 is 65K, and 40K on the W18. This is part of a brace frame. The axial load is noted to be "reversible".

((yes, I know my detail above shows a W18 and plan below shows W24... I have fixed my detail, but the issue remains))

Here is plan view:

 

[DrZoidberWoop]

I would probably end up with something like this.

 

[rowingengineer]

What is the beam receiving the joists size? Type?

 

[Agent666]

Also to simplify things can you get the load case loads. You show some sort of envelope. Either that or the brace doesn't have any load in it?

Agree with others in that a through plate is the obvious answer and most direct Loadpath. If you were to put a plate at the underside as sketched, then you also need to deal with the eccentricity of the axial load, and any differences in stiffness. For example if the proposed plate was welded to the column and beam then its going to potentially be stiffer than the face fixed end plate. Load follows stiffness.

 

[BAretired]

Why not terminate the column with a cap plate below the deeper beam and connect the two beams directly?

Alternatively, use a WF instead of HSS for a column.

BA

 

[Ben29]

Question: How do I know if the axial force is meant to "pass through" the column? The EOR is showing an axial force of +/- 110K on both sides of the column. So the way I see it, that is 220K of combined axial force if I am using the through-plate connection. The depth of the beam is limiting the height of the through-plate that I can use, thereby making this connection No Good.

 

[DrZoidberWoop]

That is a question for whoever did the structural analysis. I highly doubt they intended for the axial forces to be combined. Your maximum axial force is going to be above 110 kips because of your bracing, but it would be ridiculous for the forces to be superimposed.

 

[wrxsti]

on your drawing the force on the bracing says +/- 165k though .... the beam axial should be lower than that ... if 220k was going on somewhere at the joint
it should be reflected in the bracing force

 

[Ben29]

OK - if someone could walk me through this I would be forever grateful.
1) In my model, I enter the brace force = +/-165K
2) The program automatically calculates the beam axial force based on geometry. The axial force for the beam on the right side is calculated to be +/-117.89 K. Do I need to enter in an additional 110K transfer force on top of the 117.89K? (see circled area in snip below)
4) Now, moving over to the calculation for the left side of the column, Should I enter anything in for the Beam Axial or Transfer force? (see second snip below)

 

[wrxsti]

hey what software is that looks like idea statica

 

[Ben29]

@wrxsti, It is the new Descon Plus. (I don't love it.)

 

[wrxsti]

i like the drawing section for the connection detail

even if it sucks for analysis would be very handy for that alone


cool i'm not familiar with the software but you could experiment and see what results are looking like

maybe with quick confirmation from a standard connection table from AISC

i dont believe the transfer force in this case is superimposed on the beam axial
but maybe represents how much of the axial is transferred to the column

 

[Enable]

Sorry Ben but this is a situation where only the EOR can tell you definitively. If I had to conjecture, based on the loads that you have, I would suspect the 110k is the total lateral force for the beam line that is to be transferred to the brace and you have little if any transfer forces going on once it reaches the brace bay. Everything is marked +/- and a 165K resultant brace force translates into a horizontal component that is very close to the 110K indicated.

I would call the EOR to confirm. If they can't confirm, you assume the worst and design for the brace force + an additional 110k transfer. Who knows, maybe the beam fails when you start doing that!

Here's a quote from Handbook of Steel Connections that talks about exactly this issue

For bracing connections, in addition to providing the brace force, [the EOR should] also provide the beam shear and axial transfer force. The transfer force is the axial force that must be transferred to the opposite side of the column. The transfer force is not necessarily the beam axial force that is obtained from a computer analysis of the structure...A misunderstanding of transfer forces can lead to both uneconomic and unsafe conditions.