design of plate elements

[senthil83]

I need to design a duct plate which is subjected to a internal pressure of about 500mmWC.

while doing the plate design as per roarks formula, i found diffcult in choosing which end condition to be used

for expample, if i want to design a duct plate of 2500X3000mm x 5 thk subjected to internal pressure of 500mmWc.
and the plate is stitch welded on all four edges to a primary structural members.

The end condition i considered is fixed on all four edges for finding the spzcing of stiffener in the plate.I don't know whether it is to be considered as simply supported?

But since the stiffener are used to break the size of plate, the design of plate inbetween stiffeners are to be considered simply supported or fixed end condition?

Please calrify.

thanks

 

[BAretired]

To be conservative, consider plate simply supported at all edges and at all stiffeners.

BA

 

[dhengr]

Check with the American Society of Mechanical Engineers (ASME), American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE), maybe some power plant duct design engineering groups, and other similar engineering groups for design guides, literature and standards on duct design. Duct design is pretty well standardized and I’ll bet there are some very good design guides out there which would be most helpful to you.

I would make the plate edges somewhere btwn. fixed and pinned for there own design and nearer pinned for mid span plate design. And, I suspect you end up involved in some true thin plate/shell design considerations too. I would make the edge welds light continuous welds for two reasons. For one thing stitch welding will have you blowing stuff all over the place; and stitch welding requires much layout and inspection work, is slower welding, and all the weld starts and stops are potential stress raisers, in a vibrating plate environment. The plates are continuous over intermediate stiffeners.