natural modes frequency in each time step

[sharareh]

Hi there,
I want to have the natural modes' frequencies in each time step in the nonlinear dynamic analysis. What I have to do? (the first 2 modes are enough)
cheers,

[silvia]

i would do a loop with somethign like:

loop over:
analyze 1
eigen 2

[sharareh]

Thanks for helping m, but I still have problem. I used a loop to get the frequencies, but only the first step's frequencies are calculated and for others the following message is there:

"BandArpack Solver::Error in dgbtrf_
Warning FrequencyAlgo::Solve Current Step<>_
the eigen S0E failed in solve <>.
EigenAnalysis::analysis<>- algorithm failed"

I don't know what is the problem. Also please tell me if I want to record these frequencies in a file what the exact command is to be used.

[silvia]

the command is somethign like:

set periodFileID [open Data/Periods.m w]
puts $periodFileID Period =$Tperiod;