ShellMITC4, ShellNL, Non-Flat Shell Element

[KenLuu]

Hi everyone,

I have some question regarding shell elements developed in OpenSees. As I know the shell elements are based on the concept of non-flat (or curved, or degenerated) shell element, which was first proposed by Ahmad et al. 1970. As I understand that this type of shell element requires us to define the normal vector V3i at each node. This vector plays an important role in determining the local coordinate at each node of the element. However, I don't see any command to define the vector V3i when using ShellMITC4 as well as ShellNL. My question is whether the vector V3i is considered in the code of the shell element, or the element is a another type, not the type I mentioned?

Thank you very much!

[vesna]

Under references for the two shell elements you are mentioning you will find the papers that describe the theory they are based on. You can also look at the source code to understand their implementation: http://opensees.berkeley.edu/WebSVN/lis ... c5ca8312e2