2 questions about zero-length element

[xinyue]

Hi all, I've been thinking about two questions about zero-length element but couldn't find an answer myself. By any chance, could you show me some your insights? Thanks in advance!

Q1: The zero-length element consists of two nodes (m dof at each node) at the same location, which seems to introduce one redundant node (m dof) to the model. Consequently, I think in eigen analysis, the size of the eigenvector will increase by m. And the values of the two nodes in the same eigen vector should be the same. If I plan to use the eigen vectors to do modal analysis, should I eliminate the repetitive m entries from the eigen vectors?

Q2: If I apply a nodal load on one of the two nodes of a zero-length element, does this mean this load is also applied on the other node? (In other words, will it make any difference if applying nodal load on either node of a zero-length element?)

[mhscott]

Q1: You will need to use the equalDOF command to eliminate redundant degrees of freedom

Q2: Yes, in some cases it can make a difference

[selimgunay]

If you are using a zerolength element, it means that you are introducing a flexible element (can be interpreted as a spring) between the two nodes of a zerolength element. Therefore, obviously those two nodes will have different values in the eigenvectors

[xinyue]

If you are using a zerolength element, it means that you are introducing a flexible element (can be interpreted as a spring) between the two nodes of a zerolength element. Therefore, obviously those two nodes will have different values in the eigenvectors

Thank you for your explanation. It's so clear to me now!