3DRCframe-Vertical frequency/period/eigenvalue

[honestliang]

Hi，everyone.I have a problem,I know that there are commands to output horizontal period/eigenvalue/frequency. Is there a way to output vertical frequency/period or vertical eigenvalue in OpenSees?
set xDamp 0.05;
set nEigenI 1;
set nEigenJ 2;
set lambdaN [eigen [expr $nEigenJ]];
set lambdaI [lindex $lambdaN [expr $nEigenI-1]];
set lambdaJ [lindex $lambdaN [expr $nEigenJ-1]];
set omegaI [expr pow($lambdaI,0.5)];
set omegaJ [expr pow($lambdaJ,0.5)];
set alphaM [expr $xDamp*(2*$omegaI*$omegaJ)/($omegaI+$omegaJ)];
set betaKcurr [expr 2.*$xDamp/($omegaI+$omegaJ)];
rayleigh $alphaM $betaKcurr 0 0
set numModes 12
set lambda [eigen $numModes]
set period "Periods.txt"
set Periods [open $period "w"]
puts $Periods " $lambda"
close $Periods
record (We can use the above command to output the horizontal eigenvalue/period/frequency of the structure)

But how can we output vertical eigenvalue/period/frequency in OpenSees？
Thanks for your reply,believe the answers will help more people who are confused about that.

[mhscott]

There is no difference between "horizontal" and "vertical" periods. Periods are periods.

Define mass and stiffness in the vertical direction and you will get an eigenvalue that corresponds to vibration in the vertical direction.

[honestliang]

Thanks for your reply！