mode shapes for 3D solid brick column

[saumyashah]

what if i want to have mode shapes of a solid bridge pier i have to model it as 2D with lumped masses and then find its mode shapes? or there is any other way in opensees through which i can get mode shapes of solid 3D bridge pier

[fmk]

you have to model it .. but what you can obtain with a 2d model you can obtain with a 3d model .. so if you are able to extract from 2d you should be able to do with a 3d model using the exact same commands

[saumyashah]

dear fmk

as u said i model a 3d pier and i am getting only periods but no mode shapes i am posting my script can you please check

# Units: N, m, sec
# ----------------------------
# Start of model generation
# ----------------------------
# Create ModelBuilder with 3 dimensions and 3 DOF/node
model basic -ndm 3 -ndf 3
#--define material parameters for the model


set output out_t;

file mkdir $output;



set E 30750000000;

set v 0.2;

set G [expr $E/(2*(1+$v))];

set K [expr $E/(3*(1-2*$v))];

set density 2500;
#---yield stress
set sigY 458846.814;
#---failure surface and associativity
set rho 0.617
set rhoBar 0.617
#---isotropic hardening
set Kinf 0.0
set Ko 0.0
set delta1 0.0
#---kinematic hardening
set H 0.0
set theta 1.0
#---tension softening
set delta2 0.0



#--material models
# type tag k G sigY rho rhoBar Kinf Ko delta1 delta2 H theta density
nDMaterial DruckerPrager 1 $K $G $sigY $rho $rhoBar $Kinf $Ko $delta1 $delta2 $H $theta $density
# Define geometry
;




node 1 0.00000 0.00000 0.0000
node 2 6.900 0.00000 0.0000
node 3 6.900 12.760 0.000000
node 4 0 12.760 0.000000
node 5 0 0 2.420
node 6 6.900 0 2.420
node 7 6.900 12.760 2.420
node 8 0 12.760 2.420
node 9 6.900 18.660 0.000000
node 10 0 18.660 0.000000
node 11 6.900 18.660 6.420
node 12 0 18.660 6.420


# ele Node mat
element stdBrick 1 1 2 3 4 5 6 7 8 1

element stdBrick 2 4 3 9 10 8 7 11 12 1




recorder display ShakingBeam 0 0 300 300 -wipe
prp -100 100 120.5
vup 0 1 0
display 1 0 1


# boundary conditions
fix 1 1 1 1 0 0 0
fix 2 1 1 1 0 0 0
fix 5 1 1 1 0 0 0
fix 6 1 1 1 0 0 0

# Create the analysis object
# create the analysis

#-------------------------------------------------------

system BandGeneral



# Create the constraint handler, the transformation method

constraints Transformation



# Create the DOF numberer, the reverse Cuthill-McKee algorithm

numberer RCM

for { set k 1 } { $k <= 12 } { incr k } {
recorder Node -file [format "modes/mode%i.out" $k] -nodeRange 1 12 -dof 1 2 3 "eigen $k"
}
set lambda [eigen 12];

# calculate frequencies and periods of the structure

# calculate frequencies and periods of the structure
#---------------------------------------------------
set omega {}
set f {}
set T {}
set pi 3.141593



foreach lam $lambda {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}

puts "periods are $T"

set period "modes/Periods.txt"
set Periods [open $period "w"]
foreach t $T {
puts $Periods " $t"
}