Hello all,
I am modeling a L2x2x1/8 angle as a simple BeamColumn with a 100 lb point load acting in the vertical direction at the midpoint. The angle section is rotated such that it opens downward. In other words, the angle at 0 degrees from the vertical looks like " L ". When rotated 135 degrees clockwise, it looks like " ^ ".
If I model the element as a fiber section, I get deflections that are about four times larger than the deflections of an elasticBeamColumn element with the same material and section properties. Also, the fiber section moves somewhat horizontally, even though I am applying a vertical load. I am using the newest version (2.3.0) of the code. With the elastic section, I orient the local axes along the angle legs (and then apply the geometric transformation to rotate the section), and with the fiber section, I orient the local axes in the vertical and horizontal direction, assuming the section is already rotated 135 degrees. I assume the (0,0) point of the fiber section acts at the centroid of the section.
Included below are the elastic and fiber section files, respectively.
I appreciate in advance any suggestions or insight into why I am seeing horizontal movement and large deflections.
Thank you,
jgeis
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# Create ModelBuilder with 3 dimensions and 6 DOF/node
model basic -ndm 3 -ndf 6
# Nodal Coordinates (ft)
node 1 0.0 0.0 0.0
node 2 2.75 0.0 0.0
node 3 5.5 0.0 0.0
# Define Boundary Conditions (pin and roller)
fix 1 1 1 1 0 0 0
fix 3 0 1 1 0 0 0
# Define Geometric Transformation
set IDTopChordTransf 1
geomTransf Linear $IDTopChordTransf 0 -0.7071 -0.7071;
# Connectivity
element elasticBeamColumn 1 1 2 3.364000e-003 4.176000e+009 1.606154e+009 1.413000e-007 9.16077000e-006 9.16077000e-006 $IDTopChordTransf
element elasticBeamColumn 2 2 3 3.364000e-003 4.176000e+009 1.606154e+009 1.413000e-007 9.16077000e-006 9.16077000e-006 $IDTopChordTransf
# Applied Loads (100 lb in vertical directino at middle node)
pattern Plain 1 Linear {
load 2 0.0 0.0 -100.0 0.0 0.0 0.0
}
puts "model built"
# Output
recorder Node -file Node2.out -node 2 -dof 1 2 3 4 5 6 disp;
puts "recorders specified"
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6
algorithm Newton
integrator LoadControl 0.1
analysis Static
puts "analysis set up"
analyze 10
puts "done with analysis"
loadConst -time 0.0
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# Create ModelBuilder with 3 dimensions and 6 DOF/node
model basic -ndm 3 -ndf 6
# Nodal Coordinates (ft)
node 1 0.0 0.0 0.0
node 2 2.75 0.0 0.0
node 3 5.5 0.0 0.0
# Define Boundary Conditions (pin and roller)
fix 1 1 1 1 0 0 1
fix 3 0 1 1 0 0 1
# Creates UniaxialMaterial (E = 4.176000e+009 lb/ft^2)
set TopChordMatTag 1
uniaxialMaterial Elastic $TopChordMatTag 4.176000e+009
# Creates Section (Angle = L2x2x1/8)
set TopChordSectTag 1
section Fiber $TopChordSectTag {
patch quad $TopChordMatTag 20 20 -0.1105 -0.0609 0.0 0.0496 0.0 0.0644 -0.1178 -0.0535
patch quad $TopChordMatTag 20 20 0.0 0.0644 0.0 0.0496 0.1105 -0.0644 0.1178 -0.0535
}
# Assign torsional stiffness for 3D model
set TopChordTorsionMat 2; #ID tag for torsional section behavior
set Utorsion 1.413e-07; # torsional stiffness (J = 1.413000e-007 ft^4)
uniaxialMaterial Elastic $TopChordTorsionMat $Utorsion; # define elastic torsional stiffness
# Creates Section Aggregator to Include Torsion
set SecTag3D 3; #ID tag for combined behavior for 3D model
section Aggregator $SecTag3D $TopChordTorsionMat T -section $TopChordSectTag;
# Define Geometric Transformation
set IDTopChordTransf 1
geomTransf Linear $IDTopChordTransf 0 0 1;
# Connectivity
set numIntgrPts 5; # number of Gauss integration points for nonlinear curvature distribution
element nonlinearBeamColumn 1 1 2 $numIntgrPts $SecTag3D $IDTopChordTransf
element nonlinearBeamColumn 2 2 3 $numIntgrPts $SecTag3D $IDTopChordTransf
# Applied Loads (100 lb in vertical direction at middle node)
pattern Plain 1 Linear {
load 2 0.0 0.0 -100.0 0.0 0.0 0.0
}
puts "model built"
# Output
recorder Node -file Node2.out -node 2 -dof 1 2 3 4 5 6 disp;
puts "recorders specified"
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6
algorithm Newton
integrator LoadControl 0.1
analysis Static
puts "analysis set up"
analyze 10
puts "done with analysis"
loadConst -time 0.0
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Problems with Fiber Section
Moderators: silvia, selimgunay, Moderators
Re: Problems with Fiber Section
I found an error with one of the fiber section coordinates; when I fixed this error, the element only moves vertically and not horizontally now. However, I still cannot figure out why the vertical displacements are so large compared to the elasticBeamColumn element. Included is the updated file for the fiber section.
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# Create ModelBuilder with 3 dimensions and 6 DOF/node
model basic -ndm 3 -ndf 6
# Nodal Coordinates (ft)
node 1 0.0 0.0 0.0
node 2 2.75 0.0 0.0
node 3 5.5 0.0 0.0
# Define Boundary Conditions (pin and roller)
fix 1 1 1 1 0 0 1
fix 3 0 1 1 0 0 1
# Creates UniaxialMaterial (E = 4.176000e+009 lb/ft^2)
set TopChordMatTag 1
uniaxialMaterial Elastic $TopChordMatTag 4.176000e+009
# Creates Section (Angle = L2x2x1/8)
set TopChordSectTag 1
section Fiber $TopChordSectTag {
patch quad $TopChordMatTag 20 20 -0.110483333 -0.060866667 0.0 0.049616667 0.0 0.06435 -0.11785 -0.0535
patch quad $TopChordMatTag 20 20 0.0 0.06435 0.0 0.049616667 0.110483333 -0.060866667 0.11785 -0.0535
}
# Assign torsional stiffness for 3D model
set TopChordTorsionMat 2; #ID tag for torsional section behavior
set Utorsion 1.413e-07; # torsional stiffness (J = 1.413000e-007 ft^4)
uniaxialMaterial Elastic $TopChordTorsionMat $Utorsion; # define elastic torsional stiffness
# Creates Section Aggregator to Include Torsion
set SecTag3D 3; #ID tag for combined behavior for 3D model
section Aggregator $SecTag3D $TopChordTorsionMat T -section $TopChordSectTag;
# Define Geometric Transformation
set IDTopChordTransf 1
geomTransf Linear $IDTopChordTransf 0 0 1;
# Connectivity
set numIntgrPts 5; # number of Gauss integration points for nonlinear curvature distribution
element nonlinearBeamColumn 1 1 2 $numIntgrPts $SecTag3D $IDTopChordTransf
element nonlinearBeamColumn 2 2 3 $numIntgrPts $SecTag3D $IDTopChordTransf
# Applied Loads (100 lb in vertical direction at middle node)
pattern Plain 1 Linear {
load 2 0.0 0.0 -100.0 0.0 0.0 0.0
}
puts "model built"
# Output
recorder Node -file Node2.out -node 2 -dof 1 2 3 4 5 6 disp;
puts "recorders specified"
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6
algorithm Newton
integrator LoadControl 0.1
analysis Static
puts "analysis set up"
analyze 10
puts "done with analysis"
loadConst -time 0.0
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__________________________________________________________________________
# Create ModelBuilder with 3 dimensions and 6 DOF/node
model basic -ndm 3 -ndf 6
# Nodal Coordinates (ft)
node 1 0.0 0.0 0.0
node 2 2.75 0.0 0.0
node 3 5.5 0.0 0.0
# Define Boundary Conditions (pin and roller)
fix 1 1 1 1 0 0 1
fix 3 0 1 1 0 0 1
# Creates UniaxialMaterial (E = 4.176000e+009 lb/ft^2)
set TopChordMatTag 1
uniaxialMaterial Elastic $TopChordMatTag 4.176000e+009
# Creates Section (Angle = L2x2x1/8)
set TopChordSectTag 1
section Fiber $TopChordSectTag {
patch quad $TopChordMatTag 20 20 -0.110483333 -0.060866667 0.0 0.049616667 0.0 0.06435 -0.11785 -0.0535
patch quad $TopChordMatTag 20 20 0.0 0.06435 0.0 0.049616667 0.110483333 -0.060866667 0.11785 -0.0535
}
# Assign torsional stiffness for 3D model
set TopChordTorsionMat 2; #ID tag for torsional section behavior
set Utorsion 1.413e-07; # torsional stiffness (J = 1.413000e-007 ft^4)
uniaxialMaterial Elastic $TopChordTorsionMat $Utorsion; # define elastic torsional stiffness
# Creates Section Aggregator to Include Torsion
set SecTag3D 3; #ID tag for combined behavior for 3D model
section Aggregator $SecTag3D $TopChordTorsionMat T -section $TopChordSectTag;
# Define Geometric Transformation
set IDTopChordTransf 1
geomTransf Linear $IDTopChordTransf 0 0 1;
# Connectivity
set numIntgrPts 5; # number of Gauss integration points for nonlinear curvature distribution
element nonlinearBeamColumn 1 1 2 $numIntgrPts $SecTag3D $IDTopChordTransf
element nonlinearBeamColumn 2 2 3 $numIntgrPts $SecTag3D $IDTopChordTransf
# Applied Loads (100 lb in vertical direction at middle node)
pattern Plain 1 Linear {
load 2 0.0 0.0 -100.0 0.0 0.0 0.0
}
puts "model built"
# Output
recorder Node -file Node2.out -node 2 -dof 1 2 3 4 5 6 disp;
puts "recorders specified"
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6
algorithm Newton
integrator LoadControl 0.1
analysis Static
puts "analysis set up"
analyze 10
puts "done with analysis"
loadConst -time 0.0
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