rigidLink command

[from tongji]

rigidLink $type $masterNodeTag $slaveNodeTag

what are masterNodeTag and slaveNodeTag? and how to define them?
does they represent a node or a element?

Thank you!

[pejman_opensees]

This command is very similar to equalDOF command but of course there are differences. Master node and slave node are certainly nodes so are their corresponding tags. I think this command intrinsically and virtually generates an imaginary element which is of course rigid so that end nodes of this very so-called element are those master and slave nodes that we define in the command line.

[from tongji]

then what's the meaning of the following warning:
WARNING PlainHandler::handle<>-constraint matrix not identity,ignoring constraint for node 335
non-varyng assumed


THANK YOU!

[jaugalde]

What type of constraints handler are you using?

"The Plain Constraints command is used to enforce homogeneous single-point constraints, such as the case of homogeneous boundary conditions, where all boundary conditions are fixity.." from the manual.

Make sure you aren't using constraints Plain when using rigidLink. It took me a while to realize why I was getting similar error messages.

-Jose

[fmk]

with multipoint constraints other than those created using the equalDOF command you need o use Penalty, Transformation or Lagrange as your constraint handler.

[from tongji]

thank you ! yes, constraints Plain!
I'm simulating a frame under reverced-cyclic load,and now Iwant to use
"constraints Penalty $alphaSP $alphaMP"
i don't know if this command is adequate ,and how to select the "$alphaSP" and "$alphaMP"?

please help me! thank you again!

[fmk]

the factors to select depend on your model .. if they are too large you can have numerical problems in solution, too small and you do not get the constraint enforced adequately .. you have to play with it (check the disp at the nodes which you are trying to constrain).