The OpenSees Community

1. I suggest you refer to a text book or google "rayleigh damping":

https://www.orcina.com/webhelp/OrcaFlex ... idance.htm
https://www.usbr.gov/ssle/damsafety/Tec ... -07-03.pdf

2. It cannot, from reading the text book or above links you should understand why.

you can issue the eigen command any time you want .. if what you want is to change the rayleigh values after each analysis step you can put the calculations above inside an analysis loop that only does 1 step at a time .. thohj you might leave out the puts if in a loop as this will kill perforrmance .. any you might also check the eigen command works if your model has potential to become unstable.

while {$currentTime < $tFinal} {
# Eigen Analysis
rayleigh ......
analyze 1
}

note: the rayleigh values are for model at end of last converged step and not any trial steps.

create multiple load patterns, e.g. some for earthquake and some for wind, before the same analyze command.

the file contains the fluctuating values of the wind load in a specific direction. in a pattern you are providing reference loads. the actula load applied at a node at any time is equal to the load factor from the time series (in your case the load you want applied pecified in your file) multipled by the reference load .. so you would place a 1.0 in direction of load and a 0.0 for all other dof directions.

i.e. if want load applied in 1 dof direction load and you have a 6 dof problem:

load 86914 1.0 0.0 0.0 0.0 0.0 0.0

or if you want it applied in 2 dof direction:

load 86914 0.0 1.0 0.0 0.0 0.0 0.0

1. it is the basic stiffness method.
2. the standard K matrix (assuming you are not trying to use the penalty method to enforce constraints)
3. those large values are there I presume to get some rigid constraint enforced. In reality the terms only need to be a few orders of mag larger than
the coefficients in the stiffness matrix from other elements. You can either quickly calculate what these terms are or start small and increase the values until you are comfortable that the constraint you want is being reasonably enforced.

another option is just to, if possible, add an MP_Contraint to replace the constraint you are trying to enforce numerically. This way, assuming you are not using the Penalty method to enforce the constraints, no large numbers are needed in the tangent and the size of the tangent matrix is also reduced (which typically increases solving times)

put the elements in different regionas and assign different damping values to the different regions

i.e. end of file should look like the following with the loadConst added:

analyze 1
puts "##### STAGE 1 - finished #####";

loadConst -time 0.0

pattern Plain 2 Linear { load 1 0 -1000 0 0 0 0 }

analyze 1
puts "##### STAGE 2 - finished #####";

here is another example in our git repo
https://github.com/OpenSees/OpenSees/bl ... ays/j1.tcl

you could try another modelbuilder provided just for testing material .. here is an example i used awhile back

model UniaxialMaterialTest
uniaxialMaterial Elastic 1 3000
uniaxialMaterial MinMax 2 1 -min -0.001
uniaxialMaterial MinMax 3 1 -max 0.001
uniaxialMaterial MinMax 4 1 -min -0.001 -max 0.001

set strains {0.00 0.0005 0.001 0.002 0.001 0.0005 0.0 -0.0005 -0.0001
-0.002 0.0}

proc doStrains {matTag strains} {
puts "\n Testing $matTag"
uniaxialTest $matTag
foreach strain $strains {
strainUniaxialTest $strain
set stress [stressUniaxialTest]
set tangent [tangUniaxialTest]
puts "strain: $strain stress: $stress tangent: $tangent"
}
}
doStrains 2 $strains
doStrains 3 $strains
doStrains 4 $strains

post the script so i can see how you are modeling the elements

checking this works

the results are different because the element is "CURRENTLY" (i.e I might change this) just printing forces based on end moments and element length .. the recorder is reporting element forces which are determined from basic forces transformed by the geometric transformation .. for your example you are seeing differences due to PDelta .. if you set the transformation for the columns Linear the numbers should match.

create a load pattern with a single load on the node you wish to apply the load to .. the load actually applied during the transient analysis will be the value of the load at the node (the pseudo load) TIMES the load factor obtained from the time series.

these materials cause problems .. i have some newer materials for modeling walls .. you might even try forgetting the beam elements with these .. here is some code copied from an example put together by Dr. Petrone

# Concrete
# Parameters for the new concrete model
set E [expr 36900e6*$Pa] ;#elastic modulus
set nu 0.2 ;#Poisson ratio
set fc [expr 56.0e6*$Pa] ;#compressive yield strength
set ft [expr 5.0e6*$Pa] ;#tensile yield strength
set Ap 0.1 ;#damage material data
set An 1.5 ;#damage material data
set Bn 0.75 ;#damage material data
set Beta 0.4

nDMaterial PlasticDamageConcretePlaneStress 10 $E $nu $ft $fc $Beta $Ap $An $Bn; #Boundaries
nDMaterial PlasticDamageConcretePlaneStress 11 $E $nu $ft $fc $Beta $Ap $An $Bn; #Web

#NONLINEAR BIDIRECTIONAL Steel
# STEEL
set Steel 2
set Fy [expr 457.5e+6*$Pa]
set E [expr 200000e+6*$Pa]
set b 0.011042
set R0 20.0
set CR1 0.925
set CR2 0.15
set a1 0.0
set a2 55.0
set a3 0.0
set a4 55.0
#uniaxialMaterial Steel02 $Steel $Fy $E $b $R0 $CR1 $CR2 $a1 $a2 $a3 $a4

#uniaxialMaterial Steel4 $Steel $Fy $E -kin $b 20 0.9 0.15
#uniaxialMaterial Steel02 $Steel $Fy $E $b $R0 $CR1 $CR2 $a1 $a2 $a3 $a4
uniaxialMaterial Steel01 $Steel $Fy $E $b $a1 $a2 $a3 $a4


nDMaterial PlaneStressRebarMaterial 12 $Steel 0; #vertical
nDMaterial PlaneStressRebarMaterial 13 $Steel 90; #horizontal

# define SECTION
set t [expr 6.*2.54*0.01]; #in m

nDMaterial PlaneStressLayeredMaterial 1 3 10 $t 12 [expr $t*.0278] 13 [expr $t*.0278];# Boundaries
nDMaterial PlaneStressLayeredMaterial 2 3 11 $t 12 [expr $t*.00367*1.0] 13 [expr $t*.00367*1.0];#Web FACTOR 1.3


for {set j 0} {$j < $numX} {incr j 1} {
if {$j < $numEdge || $j >= [expr $numX-$numEdge]} {
element quad $eleTag $iNode $jNode $kNode $lNode 1.0 PlaneStress 1
} else {
element quad $eleTag $iNode $jNode $kNode $lNode 1.0 PlaneStress 2
}