About Analyze Command

[khunglongkhelua]

Dear vesna

I ran my model through a ground motion with dt = 0.02. I put Analyze 2000 steps with dt = 0.02. Then I put Analyze 1000 steps with dt 0.04. I expected to have close result between 2 running but it is not. In your example here http://opensees.berkeley.edu/wiki/index ... ver_Column the results are quite the same when I changed the Analyze from 3995 0.01 to 7990 0.005 . Is it because I did sth wrong in my model or sometimes the results could be much different and we should choose time step of the analyze coincide with dt of the ground motion ? I can send you my model if needed.

Thanks a lot.

[vesna]

You have an error somewhere in your model. If your model is as simple as mine you can post it and I will take a look.

[rasoulazadi]

hi dear vena
in pushover analysis how we determine the number of steps ? for example
set LBuilding 24.5;
set IDctrlNode 73;
set IDctrlDOF 1;
set Dmax [expr 0.02*$LBuilding ]; # maximum displacement of pushover. push to 10% drift.
set Dincr [expr 0.0001*$LBuilding ]; # displacement increment. you want this to be small, but not too small to slow analysis

# -- STATIC PUSHOVER/CYCLIC ANALYSIS

# create load pattern for lateral pushover load coefficient when using linear load pattern
pattern Plain 4 Linear {
load 23 [expr (676+0.2*294)*9*45*4.5] 0.0 0.0
load 33 [expr (676+0.2*294)*9*45*8.5] 0.0 0.0
load 43 [expr (676+0.2*294)*9*45*12.5] 0.0 0.0
load 53 [expr (676+0.2*294)*9*45*16.5] 0.0 0.0
load 63 [expr (676+0.2*294)*9*45*20.5] 0.0 0.0
load 73 [expr (768+0.2*294)*9*45*24.5] 0.0 0.0
}


set g 9.81
set x 1
#set txt [open 1.tcl w+]
# set s "pattern Plain [expr $y+1000] Linear { load $y$x [expr int([lindex $FStory [expr $y-1]])] 0 0 0 0 0 }"
#puts $txt "$s"
; # end load pattern



# ----------- set up analysis parameters
set Tol 1.0e-8; # convergence tolerance for test
source LibAnalysisStaticParameters.tcl; # constraintsHandler,DOFnumberer,system-ofequations,convergenceTest,solutionAlgorithm,integrator

# --------------------------------- perform Static Pushover Analysis
set Nsteps [expr int($Dmax/$Dincr)]; # number of pushover analysis steps


set ok [analyze $Nsteps]; # this will return zero if no convergence problems were encountered
puts " [analyze 2]"
set fmt1 "%s Pushover analysis: CtrlNode %.3i, dof %.1i, Disp=%.4f %s"; # format for screen/file output of DONE/PROBLEM analysis
if {$ok != 0} {
# if analysis fails, we try some other stuff, performance is slower inside this loop
set Dstep 0.0;
set ok 0
set i 0;
while {$Dstep <= 1.0 && $ok == 0} {
set i [expr $i+1];
set controlDisp [nodeDisp $IDctrlNode $IDctrlDOF ]
set Dstep [expr $controlDisp/$Dmax ]
set ok [analyze 1 ]

if {$ok != 0} {
puts "\n Try ModifiedNewton algorithm... \n"
algorithm ModifiedNewton -initial
test EnergyIncr 1.0e-6 1000 0
set ok [analyze 1]
algorithm $algorithmTypeStatic
if {$ok == 0} {
puts "\n ... ModifiedNewton succeed \n"
}
}

if {$ok != 0} {
puts "\n Trying Newton with Initial Tangent ... \n"
algorithm Newton -initial
test EnergyIncr 1.0e-6 1000 0
set ok [analyze 1]
algorithm $algorithmTypeStatic
if {$ok == 0} {
puts "\n ... Newton with Initial Tangent succeed \n"
}
}

if {$ok != 0} {
puts "\n Try KrylovNewton algorithm... \n"
algorithm KrylovNewton -initial
test EnergyIncr 1.0e-6 1000 0
set ok [analyze 1]
algorithm $algorithmTypeStatic
if {$ok == 0} {
puts "\n ... ModifiedNewton succeed \n"
}
}

if {$ok != 0} {
puts "\n Trying NewtonWithLineSearch ... \n"
algorithm NewtonLineSearch 0.8
test EnergyIncr 1.0e-6 1000 0
set ok [analyze 1]
algorithm $algorithmTypeStatic
if {$ok == 0} {
puts "\n ... NewtonWithLineSearch succeed \n"
}
}

if {$ok != 0} {
puts "\n Trying Broyden ... \n"
algorithm Broyden 8
test EnergyIncr 1.0e-6 1000 0
set ok [analyze 1 ]
algorithm $algorithmTypeStatic
if {$ok == 0} {
puts "\n ... Broyden succeed \n"
}

}


}; # end while loop
}; # end if ok !0

# -----------------------------------------------------------------------------------------------------
if {$ok != 0 } {
puts "PROBLEM"
} else {
puts "DONE"
}
in which part of this determined the analysis step ?
thanks

[vesna]

Number of steps depends on your target displacement and displacement increment. e.g., if you want to push your building up to displacement of 10 and your disp. increment is 0.01 you will need 1000 steps of analysis to reach your target displacement.

[khunglongkhelua]

Dear vesna

Can I send you my model through email? Thanks a lot.

[rasoulazadi]

hi
tanks a lot for replay
my problem is that if we do not use from ANALYZE command in pushover analysis how many step will done for this analyse
tanks

[vesna]

khunglongkhelua,

If the model is not too big post it here. Otherwise send it to my e-mail.

[vesna]

rasoulazadi,

Dmax/Dincr = numSteps

[rasoulazadi]

hi dear vesna
tanks a lot i find out my problem
set ok [analyze $nstep]
tanks

[rasoulazadi]

hi dear
what is difference between this two command ?
set fee1{1} 1
set fee1 1
tanks

[vesna]

I do not know if the first one works at all, but the second one assigns 1 to fee1.