Pushover Unload

[spratikbuff]

Hi All,

I want to push a structure till certain drift and then unload the structure till zero load. I am using the following script.

# 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 4; # node where disp is read for disp control
set IDctrlDOF 1; # degree of freedom read for disp control (1 = x displacement)
set Dmax [expr 0.02*$LCol]; # maximum displacement of pushover: 10% roof drift
set Dincr [expr 0.005]; # 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
#

## unloading till 0 load

set lambda [getTime]
integrator LoadControl [expr $lambda/10.]
analyze 10

The pushover part is completed successfully but while executing the unloading part I am getting the following error,

Warning: CTestNormUnbalance: : test() - failed to converge
after: 400 iterations
NewtnRaphson: : solveCurrentStep() -the ConvergenceTest object failed in test()
StaticANAlysis: : analyze()- the Algorithm failed at iteration: 0 with domain at load factor 26.0586
OpenSees > analyze failed, returned: -3 error flag

Please look into the script and let me know how to run it.

Thank you,
Supratik

[fmk]

either try more steps in the unloading or do stuff if the analysis fails.

[spratikbuff]

What do you mean by do stuff? What stuff i should the doing to run the analysis? Please help me.. I am stuck. I have increased the number of steps to 1000 and it still doesn't work.