Nonlinear secant stiffness matrix

[vesna]

Yes, define Rayleigh command within analysis loop and update the coefficient for each time step of analysis. Something like this:

set ok 0;
set controlTime 0.0;
set dt2 0.005
set dampRatio 0.02
while {$controlTime < $TmaxAnalysis && $ok == 0} {
set lambda [eigen 1]
if {$lambda <= 0} {
set T 0.0
} else {
set T [expr (2.*$pi)/sqrt($lambda)]
}
set betaK [expr 2.*$dampRatio*$T/(2.*$pi)];
rayleigh 0. 0. 0. $betaK
set ok [analyze 1 $dt2]
if {$ok != 0} {
test NormDispIncr 1.e-6 2000
algorithm Newton –initial
set ok [analyze 1 $dt2]
test NormDispIncr 1.0e-6 10
algorithm Newton
}
set controlTime [getTime]
}

[mnazari]

Thanks, I will try that.