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Deflections in Plates

Deflections in Plates

Deflections in Plates

(OP)
I am analyzing the top of a 144" long, 36" wide, and 10 gage thick rectangular steel tank as shown in the attached sketch.  There are 2-1/2" deep by 34" long stiffeners evenly spaced and welded to the underside of the plate.  The edge restraints prevent vertical movement and movement parallel to the edge, but allow movement perpendicular to the edge.  The top plate is loaded with a 3 psi upward load.  The results show much larger stresses and deflections between the last stiffener and the restrained end of the plate.  This does not make sense, but I do not know what the problem is.  
Any thoughts?
 

RE: Deflections in Plates

(OP)
I am analyzing the top of a 144" long, 36" wide, and 10 gage thick rectangular steel tank as shown in the attached sketch.  There are 2-1/2" deep by 34" long stiffeners evenly spaced and welded to the underside of the plate.  The edge restraints prevent vertical movement and movement parallel to the edge, but allow movement perpendicular to the edge.  The top plate is loaded with a 3 psi upward load.  The results show much larger stresses and deflections between the last stiffener and the restrained end of the plate.  This does not make sense, but I do not know what the problem is.  
Any thoughts?
 

RE: Deflections in Plates

You may have better success asking this question in the Cosmosforum: http://www.eng-tips.com/threadminder.cfm?pid=1183

That being said.  Does your FEA package allow for non-linear FEA?  Thin plates with large deflections are non-linear problems and are more complex than linear static analysis.

If you don't have access to a non-linear FEA package.  You might have some success with traditional hand calcs based on Timoshenko's Theory of Plates and Shells.  You may be able to find the formulas online.
 

-Dustin
Professional Engineer
Certified SolidWorks Professional
Certified COSMOSWorks Designer Specialist
Certified SolidWorks Advanced Sheet Metal Specialist
 

RE: Deflections in Plates

Looks like a boundary condition error.  Make sure that your boundaries are symmetric.  Actually why don't you use quarter symmetry and reduce your problem size?  I hope this helps.

Rob Stupplebeen

RE: Deflections in Plates

(OP)
Thanks guys.

The problems may be due to my inexperience with SolidWorks Simulation.

Shaggy PE: I did post it on the other forum.  Thanks.  The version of simulation we see does not have nonlinear analysis, but it does have large deflection capability.

stupplebeen: Used the same boundary condition for oppossite sides.  Tired symmetry but Simulation crashed.

RE: Deflections in Plates

Is the boundary condition simply supported or cantilevered?  If it simply supported, I could see the deflections being larger in the end regions than the interior ones.

Eric

RE: Deflections in Plates

(OP)
EEnd:

All the edges have the same retraint but the deflections in the two end regions are not the same.  The deflections in one of the end regions is more than double the other.

RE: Deflections in Plates

2X! It looks like boundary condition error.  Could you better explain your BCs?  You did not apply BCs as you really wanted.

Best regards,

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