UG-36(a)(1): Twisting moment of elliptical opening 1

[InspectorByDay]

Question:

Per UG-36(a)(1):

"When the long dimension of an elliptical or obround opening exceeds twice the short dimensions, the reinforcement across the short dimensions shall be increased as necessary to provide against excessive distortion due to twisting moment."

What is the twisting moment being referred to in this?

How/does Compress account for this twisting moment?

Any info would be greatly appreciated. Not sure if this problem is to be approached as a torsional moment from external loads or if it is referring to moments from internal pressure.

 

[TomBarsh]

The twisting moment occurs due to the action of the shell under internal pressure (this is somewhat resisted simply by the presence of the nozzle neck and its moment of inertia). The Code gives no direction on how to analyze this. COMPRESS will report a Deficiency message "UG-36(a)(1): More analysis is required. Additional reinforcement may be necessary as the long opening dimension exceeds twice the short dimension."

For such cases you may wish to use the FEA function built-into COMPRESS to analyze the nozzle and shell.

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Tom Barsh
Codeware Technical Support

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