Pushover Analysis Help

[spratikbuff]

Hi,

I want to do a pushover analysis upto a certain drift level. After that I want to unload the structure till zero load and do eigen value analysis at that point. Can anyone suggest me the procedure to do this analysis.

Thank you,
Supratik.

[fmk]

#pushover
integrator LoadControl or DisplacementControl
set drift 0.; set targetDrift 0.;
while {$drift < $targetDrift} {
analyze 1;
set drift [expr [nodeDisp $topNode 1]/$Height]
}

#unload
set loadFactor [getTime]
set dLambda [expr -$loadFactor/($numStep * 1.)]
integrator loadControl $dLambda
for {set i 0; $i<$numStep; incr i 1} {
analyze 1
}

#eigenvalues
puts [eigen $numMode]

[spratikbuff]

I am getting an error while running the unload part...

wrong # args: should be for "start test next command"

while executing
for {set i 0; $i<$numStep; incr i 1} {
analyze 1

Is the unload part related to the pushover part. I am using my own code for pushover analysis but not able to unload till zero load. I am attaching my pushover code. Please help me with the unloading part.


############################################################################
# Pushover Analysis #
############################################################################


# assign lateral loads and create load pattern

set lat1 0.33; # force on each frame node in Floor 1
set lat2 0.66; # force on each frame node in Floor 2
set lat3 1.00; # force on each frame node in Floor 3

pattern Plain 200 Linear {
load 4 $lat1 0.0 0.0;
load 5 $lat1 0.0 0.0;
load 6 $lat1 0.0 0.0;
load 7 $lat2 0.0 0.0;
load 8 $lat2 0.0 0.0;
load 9 $lat2 0.0 0.0;
load 10 $lat3 0.0 0.0;
load 11 $lat3 0.0 0.0;
load 12 $lat3 0.0 0.0;
}

# display deformed shape:
set ViewScale 10;
DisplayModel2D DeformedShape $ViewScale ; # display deformed shape, the scaling factor needs to be adjusted for each model

# displacement parameters
set IDctrlNode 10; # node where disp is read for disp control
set IDctrlDOF 1; # degree of freedom read for disp control (1 = x displacement)
set Dmax [expr 0.01*3*$LCol]; # maximum displacement of pushover: 10% roof drift
set Dincr [expr 0.05]; # displacement increment

# analysis commands
constraints Plain; # how it handles boundary conditions
numberer RCM; # renumber dof's to minimize band-width (optimization)
system BandGeneral; # how to store and solve the system of equations in the analysis (large model: try UmfPack)
test NormUnbalance 1.0e-6 400; # tolerance, max iterations
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
integrator DisplacementControl $IDctrlNode $IDctrlDOF $Dincr; # use displacement-controlled analysis
analysis Static; # define type of analysis: static for pushover
set Nsteps [expr int($Dmax/$Dincr)];# number of pushover analysis steps
set ok [analyze $Nsteps]; # this will return zero if no convergence problems were encountered
puts "Pushover complete"; # display this message in the command window
#

Thank You,
Supratik