2 sequence earthquake analysis

[vesna]

You need to analyze your model for larger number of analysis steps to make sure that after an earthquake it goes through the free vibrations. Following an earthquake I usually do analysis with a high damping to damp the free vibrations as soon as posible. Here I am posting the script that can do any number of earthquakes in a sequence but as an example I am only doing two analysis:

#---------------------------------------------
# Define Time Series
#---------------------------------------------
set dt [list 0.01 0.005];
set nPtE [list 25920 26400 ];

timeSeries Path 1 -dt [lindex $dt 0] -filePath GroundMotions/EQ1.dat -factor $g
timeSeries Path 2 -dt [lindex $dt 1] -filePath GroundMotions/EQ2.dat -factor $g

source LibAnalysisDynamicParameters.tcl; # constraintsHandler,DOFnumberer,system-ofequations,convergenceTest,solutionAlgorithm,integrator

set dir 1; #direction of ground motion
set noEq 2; #number of earthquakes

for { set i 1 } { $i < [expr $noEq +1] } { incr i } {
# Earthquake analysis

#Define damping
set eigenval [eigen 1]
set freq [expr $eigenval**0.5]
set dampRatio 0.02
rayleigh 0. 0. 0. [expr 2.*$dampRatio/$freq]

#define the uniform excitation
set tagTs $i
set patternTag [expr $i+10]
pattern UniformExcitation $patternTag $dir -accel $tagTs

source Recorders.tcl

#perform analysis
set DtAnalysis [lindex $dt [expr $i-1]]
set nPt [lindex $nPtE [expr $i-1]]
set TmaxAnalysis [expr $nPt*$DtAnalysis]
set ok [analyze $nPt $DtAnalysis]

source Convergence.tcl

#free vibrations with 5 times bigger damping ratio
rayleigh 0. 0. 0. [expr 5.*2.*$dampRatio/$freq]
analyze 1000 $DtAnalysis

loadConst -time 0.0

remove recorders
puts "Time hisotry #$i is done!"
}

[andreascj]

Thanks Vesna,

But how did you make sure that the 5 times larger damping that you are defining only damps out the free vibration part not the whole response history?

[vesna]

It can not damp the whole history as it is assigned to the model after the time history analysis.

[andreascj]

But your a"analyze 1000 $DtAnalysis" appears after the 5 times larger damping.

Thanks.

[vesna]

This referes to the free vibrations following the ground motion.

[andreascj]

Sorry, but where do you analyze for the rest of the ground motion? I mean, are there two "analyze" in the model?

Thanks.

[vesna]

if you read the code carefully you will find the first "analyze" command in the line before "source Convergence.tcl"

[andreascj]

Thanks Vesna, got it.