Diagonal tension of rectangular plate with a central unstiffened hole

[StevenKatzeff]

Hi,

Can anybody help me to find some information on diagonal tension analysis of a rectangular plate with a central unstiffened hole(s).

 

[ishvaaag]

You have equations in

Gide to Stability Design Criteria for Metal Structures 4th edition
edited by Theodore V. Galambos
around p.115

The same, 5th edition, around p. 151

I once posted some worksheets doing this tasks and other related to web openings but are not available anymore since it seems was against the forum policy.

Best wishes

 

[StevenKatzeff]

Thanks ishvaaq, is there a possible way for me to look at those worksheets? Until I take that book out from the library, can you tell me whether assuming an effective thickness of the panel without a hole and applying the Bruhn diagonal tension analysis will work?

 

[ishvaaag]

http://books.google.es/books?id=W_a...esult&ct=result&resnum=1#v=onepage&q=&f=false

This opens the book right more or less where wanted.

Respect the availability of the worksheets (Mathcad's) I think I posted most of them at the Collaboratory of Mathcad 2000, but I think presently public access to such site is not public anymore after Mathsoft's purchase by PTC.

I may however give a try to your specific case and see how well it fits the worksheets and see what are the results, and comment.

Those not based in Galambos' I think I based on a pair of articles on AISC's web openings steel design guide 2, 1st edition, which must be readily available.

 

[StevenKatzeff]

Ok, lets say a panel 508mm by 189mm with two central unstiffened holes of 76 mm each 200mm apart. Thickness of the panel is 3mm and the boundary conditions are: short side fully clamped, one long side clamped, one simply supported. The applied shear is 250 N/mm.
Let me know if this is enough info.

Regards,

Steven

 

[ishvaaag]

From your description I think the web opening approach from the guide will be less applicable; anyway will look. Of what you are giving to me and checking the implementation of Galambos IV I have, I am finding as of now that on the one hand we have not one ciruclar opening but two, and even simulating them as a rectangle (what is overly conservative, surely too much) the conditions that I have described in the worksheet, that exactly match I think those given in the book do not conform to your restraint. I also precise to know if the 200 mm are between hole centers or closer quadrant points. As well, since 3 mm thick, I understand the applied (factored) shear stress is 250/3=83.33 N/mm2.

With just the 4 sides supported that would give (for the long rectangle having the circles within and 200 mm between centers) a 3.95 check where we would need to have at much 1.

We are not done. Since the procedure to get the applicable critical shear stress with holes is a function of that without holes by the Galambos' quoted formulation, we may still find such stress with your proper constraints looking elsewhere; I will.

Also, some 3D model able to enter in the postbuckling strength would give the thing; those elastic, not as you pretend. Let's continue looking.

We may have

 

[StevenKatzeff]

Hi ishvaaaq,

To answer your questions, I have already obtained the shear buckling allowable with centre unstiffened holes using Fokker TH3.906. You are right, the applied shear stress is 83.3 N/mm^2. So it is clear that the panel should buckle under these conditions.
My question is:
What analysis can be done now to determine how the shear is distributed to the surrounding structure and whether diagonal tension analysis as per Bruhn is in fact applicable. I do not understand what you mean by 3.95 check, but I have not gone through Galambos yet.
Definitely FE analysis should be done.

 

[ishvaaag]

Well, I assumed Fy=260 MPa and then the applied shear stress to the shear critical stress with the holes so modeled gives ratio 3.95 in the above described conditions. Of Bruhn I can't say since (as always, and more here where so many of many fields are present) I am not particularly an expert and just try to answer what my path through my studies and practice have permitted to learn.

After reviewing somewhat the book and papers I have (UBC on aluminum, plate buckling os naval structures and eurocode steel for buildings between them) I don't find readily nor a case with your constraints, less the exact kind of geometry, then I also think that if available a FEM analysis will be the more sound approach.