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LindaBPolk, the beam I was studying is a rectangular beam, which is a part of a fixed suport portal frame. The section of the beam is uniform i.e. no reinforcement is used.

I used nonlinearBeamColumn element.

Hi,
I was studying the stresses in the sections of a beam. The stress-strain outputs changes with the number of subdivisions ( fibers ) in the section.
How can I know at what number of subdivisions ( fibers ) the outputs will be correct ?

Thanks.
The stress-strain outputs changes with the number of subdivisions ( fibers ) in the section.
How can I know at what number of subdivisions ( fibers ) the outputs will be correct ?

Hi,
I tried to get the stress across a section of a beam using element recorder ( stress-strain response ). The beam is a rectangular one. So, the C.G. is at midpoint along the depth. Hence , at the midpoint along the depth of the section the stress should be zero. But, in the output it is not coming zero. Why is it so ?

Hi,

I used dispBeamColumn element for all the members of a fixed suppport portal frame. In the results the member end moments are coming correct, but the section forces at the integration points of the beam are coming wrong ( wrong in the sense that the values of bending moments at all the sections along the beam are coming out same ). Can anyone tell me the reason for this ? I'm a beginner in Opensees. Please help me out.
The example is as below-

# Basic units are newton, metre and second
wipe ;
model BasicBuilder -ndm 2 -ndf 3;
set dataDir Data;
file mkdir $dataDir;
set GMdir "GMfiles";

node 1 0 0
node 2 0 4
node 3 2 4
node 4 2 0

fix 1 1 1 1
fix 2 0 0 0
fix 3 0 0 0
fix 4 1 1 1

uniaxialMaterial Elastic 1 200000000000

# moment of inertia of the beam is double that of the columns

section Fiber 1 {
patch quad 1 6 8 -0.15 -0.1 -0.15 0.1 0.15 0.1 0.15 -0.1
}

section Fiber 2 {
patch quad 1 6 8 -0.189 -0.1 -0.189 0.1 0.189 0.1 0.189 -0.1
}

geomTransf Linear 1 ;

element dispBeamColumn 1 1 2 5 1 1;
element dispBeamColumn 2 2 3 5 2 1
element dispBeamColumn 3 3 4 5 1 1

recorder Node -file $dataDir/DFree.out -time -node 2 3 -dof 1 2 3 disp;
recorder Node -file $dataDir/DBase.out -time -node 1 4 -dof 1 2 3 disp;
recorder Node -file $dataDir/RBase.out -time -node 1 4 -dof 1 2 3 reaction;
recorder Drift -file $dataDir/Drift.out -time -iNode 1 4 -jNode 2 3 -dof 1 -perpDirn 2 ;
recorder Element -file $dataDir/FCol.out -time -ele 1 3 globalForce;
recorder Element -file $dataDir/FBeam.out -time -ele 2 globalForce;
recorder Element -file $dataDir/ForceColSec1.out -time -ele 1 3 section 1 force;
recorder Element -file $dataDir/ForceColSec2.out -time -ele 1 3 section 2 force
recorder Element -file $dataDir/ForceColSec3.out -time -ele 1 3 section 3 force
recorder Element -file $dataDir/ForceColSec4.out -time -ele 1 3 section 4 force
recorder Element -file $dataDir/ForceColSec5.out -time -ele 1 3 section 5 force;
recorder Element -file $dataDir/DefoColSec1.out -time -ele 1 3 section 1 deformation
recorder Element -file $dataDir/DefoColSec2.out -time -ele 1 3 section 2 deformation
recorder Element -file $dataDir/DefoColSec3.out -time -ele 1 3 section 3 deformation
recorder Element -file $dataDir/DefoColSec4.out -time -ele 1 3 section 4 deformation
recorder Element -file $dataDir/DefoColSec5.out -time -ele 1 3 section 5 deformation;
recorder Element -file $dataDir/ForceBeamSec1.out -time -ele 2 section 1 force;
recorder Element -file $dataDir/ForceBeamSec2.out -time -ele 2 section 2 force
recorder Element -file $dataDir/ForceBeamSec3.out -time -ele 2 section 3 force
recorder Element -file $dataDir/ForceBeamSec4.out -time -ele 2 section 4 force
recorder Element -file $dataDir/ForceBeamSec5.out -time -ele 2 section 5 force;
recorder Element -file $dataDir/DefoBeamSec1.out -time -ele 2 section 1 deformation;
recorder Element -file $dataDir/DefoBeamSec2.out -time -ele 2 section 2 deformation;
recorder Element -file $dataDir/DefoBeamSec3.out -time -ele 2 section 3 deformation;
recorder Element -file $dataDir/DefoBeamSec4.out -time -ele 2 section 4 deformation;
recorder Element -file $dataDir/DefoBeamSec5.out -time -ele 2 section 5 deformation;

pattern Plain 1 Linear {
eleLoad -ele 2 -type -beamUniform -20000
eleLoad -ele 1 -type -beamPoint -6000 .75
eleLoad -ele 3 -type -beamPoint -6000 .25
}

constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 6 ;
algorithm Newton;
integrator LoadControl .1;
analysis Static;
analyze 10;
loadConst -time 0.0
puts "Model Built"


Please let me know where should I make the change so that I get the section forces correctly.

The example is as below-

# Basic units are newton, metre and second
wipe ;
model BasicBuilder -ndm 2 -ndf 3;
set dataDir Data;
file mkdir $dataDir;
set GMdir "GMfiles";

node 1 0 0
node 2 0 4
node 3 2 4
node 4 2 0

fix 1 1 1 1
fix 2 0 0 0
fix 3 0 0 0
fix 4 1 1 1

uniaxialMaterial Elastic 1 200000000000

# moment of inertia of the beam is double that of the columns

section Fiber 1 {
patch quad 1 6 8 -0.15 -0.1 -0.15 0.1 0.15 0.1 0.15 -0.1
}

section Fiber 2 {
patch quad 1 6 8 -0.189 -0.1 -0.189 0.1 0.189 0.1 0.189 -0.1
}

geomTransf Linear 1 ;

element dispBeamColumn 1 1 2 5 1 1;
element dispBeamColumn 2 2 3 5 2 1
element dispBeamColumn 3 3 4 5 1 1

recorder Node -file $dataDir/DFree.out -time -node 2 3 -dof 1 2 3 disp;
recorder Node -file $dataDir/DBase.out -time -node 1 4 -dof 1 2 3 disp;
recorder Node -file $dataDir/RBase.out -time -node 1 4 -dof 1 2 3 reaction;
recorder Drift -file $dataDir/Drift.out -time -iNode 1 4 -jNode 2 3 -dof 1 -perpDirn 2 ;
recorder Element -file $dataDir/FCol.out -time -ele 1 3 globalForce;
recorder Element -file $dataDir/FBeam.out -time -ele 2 globalForce;
recorder Element -file $dataDir/ForceColSec1.out -time -ele 1 3 section 1 force;
recorder Element -file $dataDir/ForceColSec2.out -time -ele 1 3 section 2 force
recorder Element -file $dataDir/ForceColSec3.out -time -ele 1 3 section 3 force
recorder Element -file $dataDir/ForceColSec4.out -time -ele 1 3 section 4 force
recorder Element -file $dataDir/ForceColSec5.out -time -ele 1 3 section 5 force;
recorder Element -file $dataDir/DefoColSec1.out -time -ele 1 3 section 1 deformation
recorder Element -file $dataDir/DefoColSec2.out -time -ele 1 3 section 2 deformation
recorder Element -file $dataDir/DefoColSec3.out -time -ele 1 3 section 3 deformation
recorder Element -file $dataDir/DefoColSec4.out -time -ele 1 3 section 4 deformation
recorder Element -file $dataDir/DefoColSec5.out -time -ele 1 3 section 5 deformation;
recorder Element -file $dataDir/ForceBeamSec1.out -time -ele 2 section 1 force;
recorder Element -file $dataDir/ForceBeamSec2.out -time -ele 2 section 2 force
recorder Element -file $dataDir/ForceBeamSec3.out -time -ele 2 section 3 force
recorder Element -file $dataDir/ForceBeamSec4.out -time -ele 2 section 4 force
recorder Element -file $dataDir/ForceBeamSec5.out -time -ele 2 section 5 force;
recorder Element -file $dataDir/DefoBeamSec1.out -time -ele 2 section 1 deformation;
recorder Element -file $dataDir/DefoBeamSec2.out -time -ele 2 section 2 deformation;
recorder Element -file $dataDir/DefoBeamSec3.out -time -ele 2 section 3 deformation;
recorder Element -file $dataDir/DefoBeamSec4.out -time -ele 2 section 4 deformation;
recorder Element -file $dataDir/DefoBeamSec5.out -time -ele 2 section 5 deformation;

pattern Plain 1 Linear {
eleLoad -ele 2 -type -beamUniform -20000
eleLoad -ele 1 -type -beamPoint -6000 .75
eleLoad -ele 3 -type -beamPoint -6000 .25
}

constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 6 ;
algorithm Newton;
integrator LoadControl .1;
analysis Static;
analyze 10;
loadConst -time 0.0
puts "Model Built"


Please let me know where should I make the change so that I get the section forces correctly.

Hi,
I used dispBeamColumn element for all the members of a fixed suppport portal frame. In the results the member end moments are coming correct, but the section forces at the integration points of the beam are coming wrong ( wrong in the sense that the values of bending moments at all the sections are coming out same ). Can anyone tell me the reason for this ? I'm a beginner in Opensees. Please help.

The example is as below-

# Basic units are newton, metre and second
wipe ;
model BasicBuilder -ndm 2 -ndf 3;
set dataDir Data;
file mkdir $dataDir;
set GMdir "GMfiles";

node 1 0 0
node 2 0 4
node 3 2 4
node 4 2 0

fix 1 1 1 1
fix 2 0 0 0
fix 3 0 0 0
fix 4 1 1 1

uniaxialMaterial Elastic 1 200000000000

# moment of inertia of the beam is double that of the columns

section Fiber 1 {
patch quad 1 6 8 -0.15 -0.1 -0.15 0.1 0.15 0.1 0.15 -0.1
}

section Fiber 2 {
patch quad 1 6 8 -0.189 -0.1 -0.189 0.1 0.189 0.1 0.189 -0.1
}

geomTransf Linear 1 ;

element dispBeamColumn 1 1 2 5 1 1;
element dispBeamColumn 2 2 3 5 2 1
element dispBeamColumn 3 3 4 5 1 1

recorder Node -file $dataDir/DFree.out -time -node 2 3 -dof 1 2 3 disp;
recorder Node -file $dataDir/DBase.out -time -node 1 4 -dof 1 2 3 disp;
recorder Node -file $dataDir/RBase.out -time -node 1 4 -dof 1 2 3 reaction;
recorder Drift -file $dataDir/Drift.out -time -iNode 1 4 -jNode 2 3 -dof 1 -perpDirn 2 ;
recorder Element -file $dataDir/FCol.out -time -ele 1 3 globalForce;
recorder Element -file $dataDir/FBeam.out -time -ele 2 globalForce;
recorder Element -file $dataDir/ForceColSec1.out -time -ele 1 3 section 1 force;
recorder Element -file $dataDir/ForceColSec2.out -time -ele 1 3 section 2 force
recorder Element -file $dataDir/ForceColSec3.out -time -ele 1 3 section 3 force
recorder Element -file $dataDir/ForceColSec4.out -time -ele 1 3 section 4 force
recorder Element -file $dataDir/ForceColSec5.out -time -ele 1 3 section 5 force;
recorder Element -file $dataDir/DefoColSec1.out -time -ele 1 3 section 1 deformation
recorder Element -file $dataDir/DefoColSec2.out -time -ele 1 3 section 2 deformation
recorder Element -file $dataDir/DefoColSec3.out -time -ele 1 3 section 3 deformation
recorder Element -file $dataDir/DefoColSec4.out -time -ele 1 3 section 4 deformation
recorder Element -file $dataDir/DefoColSec5.out -time -ele 1 3 section 5 deformation;
recorder Element -file $dataDir/ForceBeamSec1.out -time -ele 2 section 1 force;
recorder Element -file $dataDir/ForceBeamSec2.out -time -ele 2 section 2 force
recorder Element -file $dataDir/ForceBeamSec3.out -time -ele 2 section 3 force
recorder Element -file $dataDir/ForceBeamSec4.out -time -ele 2 section 4 force
recorder Element -file $dataDir/ForceBeamSec5.out -time -ele 2 section 5 force;
recorder Element -file $dataDir/DefoBeamSec1.out -time -ele 2 section 1 deformation;
recorder Element -file $dataDir/DefoBeamSec2.out -time -ele 2 section 2 deformation;
recorder Element -file $dataDir/DefoBeamSec3.out -time -ele 2 section 3 deformation;
recorder Element -file $dataDir/DefoBeamSec4.out -time -ele 2 section 4 deformation;
recorder Element -file $dataDir/DefoBeamSec5.out -time -ele 2 section 5 deformation;

pattern Plain 1 Linear {
eleLoad -ele 2 -type -beamUniform -20000
eleLoad -ele 1 -type -beamPoint -6000 .75
eleLoad -ele 3 -type -beamPoint -6000 .25
}

constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 6 ;
algorithm Newton;
integrator LoadControl .1;
analysis Static;
analyze 10;
loadConst -time 0.0
puts "Model Built"


Please let me know where should I make the change so that I get the section forces correctly.

Hi,
I used dispBeamColumn element for all the members of a fixed suppport portal frame. In the results the member end moments are coming correct, but the section forces at the integration points of the beam are coming wrong ( wrong in the sense that the values of bending moments at all the sections are coming out same ). Can anyone tell me the reason for this ? I'm a beginner in Opensees. Please point out where have I made the mistake.