Deal All,
I have modeled a simple 3D 1-floor, 4-columns RC building with fiber sections and nonlinear beamcolumn elements, incorporating elastic torsional stiffness in each fiber command like this ##section Fiber $secTag <-GJ $GJ> {...##
and using a section aggregator for every fiber section in order to account for shear interaction.
I performed an Eigen Analysis and what I get is very unreasonable natural periods of about 117 sec!
I can't see where the error is in the model. Could anybody give me some help here?
This is my code:
model BasicBuilder -ndm 3 -ndf 6
node 1 0 0 0
node 2 6 0 0
node 3 0 5 0
node 4 6 5 0
node 5 0 0 4.73
node 6 0 5 4.73
node 7 6 0 4.73
node 8 6 5 4.73
node 9 3 2.5 4.73
mass 9 116.947598394147 116.947598394147 0.001 0.001 0.001 594.483625170247
rigidDiaphragm 3 9 5 6 7 8
fix 1 1 1 1 1 1 1
fix 2 1 1 1 1 1 1
fix 3 1 1 1 1 1 1
fix 4 1 1 1 1 1 1
fix 9 0 0 1 1 1 0
geomTransf Linear 1 0 1 0
geomTransf Linear 2 0 0 -1
#Materials#
uniaxialMaterial Concrete01 1 -20000 -0.002 -4000 -0.00621052631578947
uniaxialMaterial Steel01 2 500000 200000000 0.01
# confined concrete for C1 #
uniaxialMaterial Concrete01 3 -20000.85953975 -0.002000085953975 -4000 -0.00810097375551405
# confined concrete for C2 #
uniaxialMaterial Concrete01 4 -20000.85953975 -0.002000085953975 -4000 -0.00810097375551405
# confined concrete for C3 #
uniaxialMaterial Concrete01 5 -20000.85953975 -0.002000085953975 -4000 -0.00810097375551405
# confined concrete for C4 #
uniaxialMaterial Concrete01 6 -20000.85953975 -0.002000085953975 -4000 -0.00810097375551405
# For shear section aggregator
uniaxialMaterial Elastic 7 2013083.33
uniaxialMaterial Elastic 8 1258177.083
#Fiber section for Column C1 #
section Fiber 1 -GJ 66146.1902222223 {
layer straight 2 2 0.000314159265358979 -0.205 0.155 0.205 0.155
layer straight 2 2 0.000314159265358979 -0.205 -0.155 0.205 -0.155
patch rect 3 8 8 -0.205 -0.155 0.205 0.155
patch rect 1 8 2 -0.25 0.155 0.25 0.2
patch rect 1 8 2 -0.25 -0.2 0.25 -0.155
patch rect 1 2 8 -0.25 -0.155 -0.205 0.155
patch rect 1 2 8 0.205 -0.155 0.25 0.155
}
# section Aggregator $secTag $matTag1 $dof1 $matTag2 $dof2 ....... <-section $sectionTag>
section Aggregator 21 7 Vy -section 1
#Fiber section for Column C2 #
section Fiber 2 -GJ 66146.1902222223 {
layer straight 2 2 0.000314159265358979 -0.205 0.155 0.205 0.155
layer straight 2 2 0.000314159265358979 -0.205 -0.155 0.205 -0.155
patch rect 4 8 8 -0.205 -0.155 0.205 0.155
patch rect 1 8 2 -0.25 0.155 0.25 0.2
patch rect 1 8 2 -0.25 -0.2 0.25 -0.155
patch rect 1 2 8 -0.25 -0.155 -0.205 0.155
patch rect 1 2 8 0.205 -0.155 0.25 0.155
}
section Aggregator 22 7 Vy -section 2
#Fiber section for Column C3 #
section Fiber 3 -GJ 66146.1902222223 {
layer straight 2 2 0.000314159265358979 -0.205 0.155 0.205 0.155
layer straight 2 2 0.000314159265358979 -0.205 -0.155 0.205 -0.155
patch rect 5 8 8 -0.205 -0.155 0.205 0.155
patch rect 1 8 2 -0.25 0.155 0.25 0.2
patch rect 1 8 2 -0.25 -0.2 0.25 -0.155
patch rect 1 2 8 -0.25 -0.155 -0.205 0.155
patch rect 1 2 8 0.205 -0.155 0.25 0.155
}
section Aggregator 23 7 Vy -section 3
#Fiber section for Column C4 #
section Fiber 4 -GJ 66146.1902222223 {
layer straight 2 2 0.000314159265358979 -0.205 0.155 0.205 0.155
layer straight 2 2 0.000314159265358979 -0.205 -0.155 0.205 -0.155
patch rect 6 8 8 -0.205 -0.155 0.205 0.155
patch rect 1 8 2 -0.25 0.155 0.25 0.2
patch rect 1 8 2 -0.25 -0.2 0.25 -0.155
patch rect 1 2 8 -0.25 -0.155 -0.205 0.155
patch rect 1 2 8 0.205 -0.155 0.25 0.155
}
section Aggregator 24 7 Vy -section 4
#Fiber sections for beam B1 #
section Fiber 5 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 6 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 7 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
#Fiber sections for beam B2 #
section Fiber 8 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 9 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 10 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
#Fiber sections for beam B3 #
section Fiber 11 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 12 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 13 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
#Fiber sections for beam B4 #
section Fiber 14 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 15 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
section Fiber 16 -GJ 21606.5300835504 {
layer straight 2 2 0.0002 0.083 -0.208 -0.083 -0.208
layer straight 2 2 0.0002 -0.083 0.208 0.083 0.208
patch rect 1 8 8 0.083 0.208 -0.083 -0.208
patch rect 1 8 2 0.125 0.25 -0.125 0.208
patch rect 1 8 2 0.125 -0.208 -0.125 -0.25
patch rect 1 2 8 0.125 0.208 0.083 -0.208
patch rect 1 2 8 -0.083 0.208 -0.125 -0.208
}
#Beam elements#
element nonlinearBeamColumn 1 5 6 4 -sections 5 6 6 7 2
element nonlinearBeamColumn 2 5 7 4 -sections 8 9 9 10 2
element nonlinearBeamColumn 3 7 8 4 -sections 11 12 12 13 2
element nonlinearBeamColumn 4 6 8 4 -sections 14 15 15 16 2
#Column elements#
element nonlinearBeamColumn 5 1 5 4 21 1
element nonlinearBeamColumn 6 2 7 4 22 1
element nonlinearBeamColumn 7 3 6 4 23 1
element nonlinearBeamColumn 8 4 8 4 24 1
set lambda [eigen -fullGenLapack 3]
set omega {}
set f {}
set T {}
set pi 3.14159265359
foreach lam $lambda {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}
Huge periods for fiber model w/ shear & torsion interaction
Moderators: silvia, selimgunay, Moderators
Re: Huge periods for fiber model w/ shear & torsion interact
did you try with elastic materials before the nonlinear ones .. if same problem, use elastic elements to see if you got your section definitions correct. if different prolem, see what happens without the aggregator.
Re: Huge periods for fiber model w/ shear & torsion interact
fmk wrote:
> did you try with elastic materials before the nonlinear ones .. if same
> problem, use elastic elements to see if you got your section definitions
> correct. if different prolem, see what happens without the aggregator.
Dear fmk, thank you for your reply.
I checked the fiber section definitions, they are perfectly correct.
I tried using double section aggregator to account for shear and torsion
#section Aggregator $secaggTag $shearMat Vy $TorMat T -section $secTag
and it works fine.
So it seems that there is an incombatibility between the direct torsional stiffness <-GJ > command and the section aggregator command that gives unreasonable results for fiber-based elements.
If anyone else could confirm this, I would appreciate it.
> did you try with elastic materials before the nonlinear ones .. if same
> problem, use elastic elements to see if you got your section definitions
> correct. if different prolem, see what happens without the aggregator.
Dear fmk, thank you for your reply.
I checked the fiber section definitions, they are perfectly correct.
I tried using double section aggregator to account for shear and torsion
#section Aggregator $secaggTag $shearMat Vy $TorMat T -section $secTag
and it works fine.
So it seems that there is an incombatibility between the direct torsional stiffness <-GJ > command and the section aggregator command that gives unreasonable results for fiber-based elements.
If anyone else could confirm this, I would appreciate it.