Connect Plate to HSS Tube 1

[dik]

Does anyone have a quick solution to attach the plate shown to the tube shown? Solution would include stability of the plate and effect of the moment from the plate on the HSS tube.

Dik

 

[skeletron]

You could try a through plate in one direction and then have welded plates in the orthogonal direction.
Check the HSS limit states using DG24 or Packer & Henderson.

Perhaps a bracket type connection. I believe CastConnex (sp?) offers this type of solution.

There are also Hollo-bolts to check out, although I'm not a huge believer. Welding the plates is tricky, but not impossible.

 

[dik]

I've been presented with this as the problem and have to verify that it can be done. I haven't found anything that looks like the type of connection. The AISC design guide example, is similar, but uses tables in the AISC manual... I'm looking for a solution that I can calculate. I could't find anything in Packer's text. He has axial loads, but not moments. I would have thought this was common... maybe not.


Dik

 

[KootK]

For fin stability, I might try strut and tie and check the diagonal as a column. For the tube walls, I second the AISC design guide. I believe Packer was involved in that too and it's about as straight forward as it's likely to get. Tell us what table you need and we'll post it here.

To what extent will the load source stabilize or destabilize the fins laterally?

 

[Lomarandil]

Could you even work in some sort of notched/cut out through plate in both directions (excuse the ASCII art below)? I suppose that depends on what diameter of HSS you have to work with, or you'd end up over-cutting the pipe slots to get the plate notches around each other

|------------------|
|    __________    |
|___/          \___|

----
just call me Lo.

 

[r13]

Have you checked AISC specification for the design of hollow structure sections? There should have solution for this (similar to pipe column connection).

 

[DrZoidberWoop]

AISC SCM 15th, Pg. 10-153: "As long as the HSS wall is not classified as a slender element, the local distortion caused by the single-plate connection will be insignificant in reducing the column strength of the HSS..... Single plate connections may be used with round HSS as long as they are non-slender under axial load (D/t<=0.11E/Fy). Yielding (plastification) off the HSS face has not been a governing limit state in physical tests. Punhcing shear/shear rupture should be checked as follows (Eq. 10-7a)."

Hope that helps. I'd check the above, the eccentric weld group, and then plate checks.

 

[dik]

I found the attached...

I've not been able to find the attachment of a thin plate to a round HSS in either the AISC referenced or Packer's book.




Dik

 

[r13]

Dik,

See p.12, example 2.2, of the linked design guide. Link

 

[r13]

Also, I think a FEM verification will be very helpful for this case.

 

[dik]

retired13: thanks... The AISC design guide example, is similar, but uses tables in the AISC manual... I'm looking for a solution that I can calculate. Does the AISC manual have a description of how they arrive at the tabular data?


Dik

 

[dik]

retired13: "Also, I think a FEM verification will be very helpful for this case." This would be OK if it were for several projects... not a single 'knock off'.

Do you know of a formula (couldn't find it in Rourks) for a cantilevered plate, loaded at the top in the stiff direction fixed at the side and at the top against rotation and translation. The top of the plate has an HP section welded to it, providing the load. It's so much stiffer than the 'fin plate' that it could easily be treated as a fixed condition.



Dik

 

[r13]

dik,

I think moment capacity check was preclude for round HSS with simple shear tab connection. I suggest the following steps to design the connection:

1. Trail select a plate size thru buckling criteria.
2. Calculate weld demand, and select weld size, thru conventional method (I don't think you need assistance from AISC table).
3. Go to paper table 2-3 (p.9) to get minimum plate thickness (t_min) per weld size selected.
4. Go to paper table 7-1 (p.79) to fine tune plate thickness and HSS wall thickness. (Please read CH7 opening statements)

This is not a straight forward method, but should work out fine, unless you have other complications.

 

[dik]

retired 13... it was items 3 and 4 that I was trying to avoid... wanting to add the info into a program that would calculate same.


Dik

 

[r13]

Dik,

Let's try this.

If you can embed the tables in the program, and require the user to input trail thickness, then ... Well you are the programer

 

[r13]

dik,

I believe you have already noticed that the guide actually ignores effects from both flexural and punching shear on the HSS, as long as the HSS wall is thinner than the shear tab, which should yield first (F_u/F_yp is a constant always > 1). This may simplify your programming quite a bit.

 

[r13]

dik,

BTY, I believe the equation and parameters in the example should be identical to the Blodgett design for eccentrically loaded weld group. Check it out, if you have access to it.

 

[dik]

retired13: Thanks very much... wish I could give you two stars...


Dik

 

[r13]

dik,

You are welcome. Glad to be helpful.

 

[r13]

dik,

Found the background material of ignore punching shear from CIDECT Design Guide 9. Link to the source,

https://www.aisc.org/technical-resources/cidect-design-guides/

Over a wide range of connections tested by Sherman (1995, 1996), only one limit state was identified for the RHS column. This was a punching shear failure related to end rotation of the beam when a thick shear plate was joined to a relatively thin-walled RHS. Two connections failed when the shear plate pulled out from the RHS wall at the top of the plate around the perimeter of the welds. A simple criterion to avoid this failure mode is to ensure that the tension resistance of the plate under axial load (per unit plate length) is less than the shear resistance of the RHS wall along two planes (per unit plate length). Thus (Sherman 1995, AISC 1997), ø1 f,p,y tp · (unit length) < 2 ø2 (0.60fc,u) tc · (unit length)

In the above inequality the left hand side, the tensile strength of the plate, is multiplied (for limit states design) by a resistance factor of ø1 = 0.9 for yielding. The right hand side of the inequality, the shear strength of the RHS wall, (for which the ultimate shear stress is taken to be 0.6 of the ultimate tensile stress), is multiplied by a resistance factor of ø2 = 0.75 for punching shear failure (AISC 1997).

Hence tp < (fc,u/fp,y) tc