Analyze as Thin shell, Plate or membrane 2

[dgkhan]

I have a 0.06 inch thick plate 44 inch x 24 inch. It is supported at perimeter with HSS 2x2. I have to check how much UDL this plate can take. I am using older version of SAP. Shall I assign it as thin shell, plate or membrane or shall I analyze it manually as a thin strip (beam)

 

[hokie66]

You say you can handle the welds. So direct your attention to them. The capacity of the welds, along with the bending capacity of the frame, will determine how much load your trolley can support. But the loading configuration will also be important. The sheet (not plate) will deflect immediately upon application of load, transferring the load closer to the edges, provided the load is not fluid.

 

[dgkhan]

rb1957
Using Roarks 6th edition. I get 35 PSF or q (load per unit area). Keeping sigma ( bending stress in plate 21 ksi).
What will be the tension on ends of plate which weld and faring HSS needs to beasr.

 

[dgkhan]

Formula is sigma = Beta x q x b2 / t2
Where
Beta is .57 (for a = 44 and b= 24 inch)
q = load per unit area
b = short side = 24 inch
t = thickness of plate = 0.06 inch.
So i kept sigma as 21 ksi and got q

 

[rb1957]

35*(44/12*2) = 257 lbs ... doesn't sound like much ...

shear on the welds looks like 60 lbs each. the tension on the welds is due to the sheet reacting the pressure with in-plane tension stresses, and these would collect at the corner welds (being the only thing connecting the sheet to the rest of the world.

check with roark about the deflection in the middle of the panel, i think it'll be more than 2*thk (so i wouldn't want to apply a plate formulae, which is what i'm assuming you've pulled from roark, as you talk about bending stresses) ...

but if 257 lbs does it for you (and how you want to use this thing), it doesn't sound unreasonable ... can you imagine one or two people standing on it ?

 

[dgkhan]

Deflection is 1.25 inches. By the way the formula you referred in previous reply was also for plate?
"from roark 4th ed pg239 (flat plate solution 81), a square plate a (= sqrt(b*d)?) loaded by pressure (uniformly distributed weight) = W/bd."

 

[rb1957]

yes, you're using plate bending equations (probably says that at the beginning of the table, talking about beinding stresses certainly suggests plate). a deflection of >1" is unreasonable for 0.06" sheet (the equations collapse long before then).

i'd suggest taking a strip along the diagonal deflect it in the middle by say 0.5" and see what the tension is to support a distributed load ... this'll also show you the (tension) loading on the welds. I suspect in your case this might be alittle high.

have you built one of these things ? why not test it ? (stand on it, with a friend if you're feeling lucky!)

 

[dgkhan]

rb1957
Please see page 245 and Table on Page 246.
This table is when using ordinary elastic equations; deflection is more than half the thickness of plate. But I am having hard time to use the table. You have any wisdom for this?