Updating model properties during time history analysis

[alima2065]

Hello everybody;
I would be appreciated if you answer my question about time history analysis. Is there any way to change some model properties (loads, materials, or some modeling parameters) during a transient analysis in a certain time step? can I use a loop to do analysis step by step and change some characteristics of the model? For example, if I put eigen command in each loop and then recall Rayleigh command, the damping will be calculated based on new coefficients and updated stiffness matrix or not? please see code blew for clarification:

for {set j 1} {$j<3995} {incr j 1} {
analyze 1 0.01
############################################################################
# Eigenvalue Analysis
############################################################################
set pi [expr 2.0*asin(1.0)]; # Definition of pi
set nEigenI 1; # mode i = 1
set nEigenJ 2; # mode j = 2
set lambdaN [eigen [expr $nEigenJ]]; # eigenvalue analysis for nEigenJ modes
set lambdaI [lindex $lambdaN [expr 0]]; # eigenvalue mode i = 1
set lambdaJ [lindex $lambdaN [expr $nEigenJ-1]]; # eigenvalue mode j = 2
set w1 [expr pow($lambdaI,0.5)]; # w1 (1st mode circular frequency)
set w2 [expr pow($lambdaJ,0.5)]; # w2 (2nd mode circular frequency)
set T1 [expr 2.0*$pi/$w1]; # 1st mode period of the structure
set T2 [expr 2.0*$pi/$w2]; # 2nd mode period of the structure
puts $Periods "$T1 $T2"

# Rayleigh Damping
calculate damping parameters
set zeta 0.02; # percentage of critical damping
set a0 [expr $zeta*2.0*$w1*$w2/($w1 + $w2)]; # mass damping coefficient based on first and second modes
set a1 [expr $zeta*2.0/($w1 + $w2)]; # stiffness damping coefficient based on first and second modes
region 1 -eleRange 1 6 -rayleigh 0.0 0.0 $a1 0.0; # assign stiffness proportional damping to frame beams & columns w/ n modifications
region 2 -node 3 4 5 6 -rayleigh $a0 0.0 0.0 0.0; # assign mass proportional damping to structure (assign to nodes with mass)

}

Thanks a lot.

[fmk]

the damping will change if the model goes nonlinear or you add or remove elements with the code you have provided.

[alima2065]

Many thanks for the reply.