why do you specify lateral load in Push Analysis...

[laura83]

why do you specify lateral load in pushover analysis if you impose a displacement control, infact the results don't change if i insert 200 N or 200000N as lateral load.
Why?
Which operation does lateral load suffer in this analysis?
Why does Rbase is constant even if I change the value of lateral load?

[silvia]

the lateral load you assign defines the distribution of the lateral loads. OpenSees will slowly apply a factor of that load and will iterate on that factor until it reaches the displacement you want.
hence, the absolute value of that load does not matter.

[laura83]

it' clear.
but i want to apply a horizontal force at free node for see the displamente of this , so I create a load lateral in this way:
but which does convergence test I must use in this particular case?

# lateral load
pattern Plain 200 Linear {
load 2 2670260 0.0 0.0 0.0 0.0 0.0
}


constraints Plain; # how it handles boundary conditions
numberer Plain; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral; # how to store and solve the system of equations in the analysis
set Tol 1.e-8; # Convergence Test: tolerance
set maxNumIter 6; # Convergence Test: maximum number of iterations that will be performed before "failure to converge" is returned
set printFlag 0; # Convergence Test: flag used to print information on convergence (optional) # 1: print information on each step;
set TestType EnergyIncr; # Convergence-test type
test $TestType $Tol $maxNumIter $printFlag;
test NormDispIncr $Tol 6 ; # determine if convergence has been achieved at the end of an iteration step
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
integrator LoadControl 0.1 1 0.1 0.1; # determine the next time step for an analysis
analysis Static; # define type of analysis static or transient
analyze 10; # apply gravity

loadConst -time 0.0

puts " analisi"

[silvia]

the convergence test is independent of the load, in a way.
i always like to check energy because it takes both load and displacement into account.

[laura83]

is it right?
# lateral load
pattern Plain 200 Linear {
load 2 2670260 0.0 0.0 0.0 0.0 0.0
}


constraints Plain; # how it handles boundary conditions
numberer Plain; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral; # how to store and solve the system of equations in the analysis
set Tol 1.e-8; # Convergence Test: tolerance
set maxNumIter 6; # Convergence Test: maximum number of iterations that will be performed before "failure to converge" is returned
set printFlag 0; # Convergence Test: flag used to print information on convergence (optional) # 1: print information on each step;
set TestType EnergyIncr; # Convergence-test type
test $TestType $Tol $maxNumIter $printFlag;
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
set Nstepload 10;
set Dload [expr 1./$Nstepload];
integrator LoadControl $Dload; # determine the next time step for an analysis
analysis Static; # define type of analysis static or transient
analyze 10; # apply gravity

loadConst -time 0.0

puts " analisi"

[silvia]

please look at example 3 in the examples manual for the pushover analysis script.