Error in Dynamic Analysis

[bmobashe]

I am trying to model pile , pile cap and column in 2D. I got the T for static analysis but in dynamic part he gives me this type of error:

ArpackSolver::Error with _saupd info = -1
N must be positive.
WARNING DirectIntegrationAnalysis::eigen() - EigenSOE failed in solve()
missing function argument at _@_
in expression "pow(_@_,0.5)"
(parsing expression "pow(,0.5)")

Could you please help me with that?

Thanks,
Bahareh

[vesna]

You have problem with eigen analysis. The solver you are using can not solve your problem. Can you show me your mass command?

[bmobashe]

Thank you for your reply. I assigned mass only to the node on the top of the column.My mass command is:

mass 8 $mconc $mconc $mconc;

Do you think this error can happen because of using metric units?

Thanks

[vesna]

There can not be problem with units as OpenSees is unitless. There is problem with your model (not enough constraints) or with a solver. If in the eigen analysis you use default solver (-genBandArpack) than you may have a problem with your model.