Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations waross on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!

why there is no drilling stiffness in QUAD4?

Status
Not open for further replies.

jsboy

Mechanical
Feb 25, 2003
20
0
0
JP
I have been using Nastran for many years and know that there is no rotational stiffness about its normal axis to it when using QUAD element(I know QUADR has drilling stiffness). Would anyone please tell me what is a theoretical reason why a rotational stiffness is not involed in traditional shell formulation? I have read some FEM books about this but none of them cleary say this reason. I am talking about linear physics only.
 
Replies continue below

Recommended for you

Shell theory does not account for this. It's just not part of the theoretical formulation. This is similar to asking the question "why don't CHEXAs account for rotation"--same reason. (Note that I'm not being flip; this is the answer).

However, when this shell theory is applied to FEA, this mode becomes relevant and must be addressed (or the dof must be omitted).

Brad
 
It is assumed that the in-plane torsional stiffness of a shell is infinite and is therefore not required. Some codes do include this 6th freedom though.
 
Status
Not open for further replies.
Back
Top