eigen comand and damping

vsuarez · Post by **vsuarez** » Mon Aug 22, 2005 5:41 pm

I am trying to perform a time history analysis over a SDOF system with stiffness proportional damping, and I get the following error message:

BandArpackSolver::Error with _saupd info = -9999
Could not build an Arnoldi factorization.IPARAM(5) returns the size of the curre
nt Arnoldi
factorization. The user is advised to check thatenough workspace and array stora
ge has been allocated.
Warning FrequencyAlgo::solveCurrentStep() - the EigenSOE failed in solve().
EigenAnalysis::analyze() - algorithm failed

Can anybody help me, please?

silvia · Post by **silvia** » Mon Aug 22, 2005 6:00 pm

sorry, this is a little problem with the eigensolver,

please view the following post:
http://opensees.berkeley.edu/community/ ... .php?t=384

and let me know if the add'l mass fixes your problem.

vsuarez · Post by **vsuarez** » Tue Aug 23, 2005 10:04 am

Yes, the problem went away when I added mass to the other DOF in the node. Thanks a lot.

Now, with regard to damping: I am not sure how to specify tangent stiffness proportional damping using the Rayleigh command. Should I use $betaK or $betaKcomm ?

Regards,

Vinicio

silvia · Post by **silvia** » Thu Aug 25, 2005 8:21 am

it depends on which tangent you want to be proportional to. the committed one? the initial (typical, i think) or the one at the step? it all depends on your model.