recorder element

[GALLO ANTONIO]

Hi, I have a problem.
Below is the my problem:
recorder Element-xml-$ datadir / FCol.out-time-ele 1 basicForces
What are basicForces?
It refers to a section of the element or a point of integration?

recorder Element-xml-$ datadir / FCol.out-time-ele 1 basicDeformation
What are basicDermation?
It refers to a section of the element or a point of integration?

recorder Element-xml-$ datadir / FCol.out-time-ele 1 plasticDeformation
What are plasticDermation?
It refers to a section of the element or a point of integration?

Thanks

[vesna]

basicForces are forces at element ends (nodes i and j) that corresponds to basic degrees of freedom (e.g., if in 2D these are axial force at node j, moment at node i, and moment at node j).

basicDermation are deformation that correspond to basic degrees of freedom (e.g., if in 2D these are axial displacement at node j, rotation at node i, and rotation at node j).

plasticDermation are plastic deformation of an element (e.g., if in 2D these are plastic axial displacement at node j, plastic rotation at node i, and plastic rotation at node j).

[GALLO ANTONIO]

thanks so much

[GALLO ANTONIO]

Hi, I have another question.
How to calculate the rotation of the element to the rope?
thanks so much.

[vesna]

What is rope?

[GALLO ANTONIO]

The rotation is the chord rotation than the inflection point where the shear stress is zero (for example in the column).
If I have a portal shear type the chord rotation is calculated as the difference in displacement between the two nodes divided by the length of cut.
The cutting length is about half the height of the column.
Thanks.

[vesna]

To calculate it you will have to use two recorders: one for node displacements and one for element basicDeformation. With node disp recorder you can get the total rotation at node i of an element. With element basicDeformation recorder you can get rotation of node i from the chord (in deformed state of the element) to the tangent of the node (in deformed state of the element). If you are in 2D and you include time in your recorder this basic deformation will be in the third column of the output file. To get chord rotation you have to subtract basic rotation from the total rotation at the node.

[GALLO ANTONIO]

Thanks so much

[gersi]

Hello,
I am in trouble as I cannot find the chord rotation demand of the elements (beam and columns) of my 2D Reinforced Concrete frame model in Opensees subjected to an Incremental Dynamic Analysis. I have used "element nonlinearBeamColumn" command to define each member but I don't know whether to apply "basicDeformation recorder" or "chordDeformation" or "section deformation recorder" ecc. in order to get the chord rotation values of each member end (Please Note that: The chord rotation at a member end is the angle between the normal to the member section there and the chord connecting the two member ends [Fardis MN (2009)].

For example :

recorder Element -file $dataDir/chord.txt -time -ele 1 basicDeformation;
or
recorder Element -file $dataDir/chord.txt -time -ele 1 chordDeformation;
or
recorder Element -file $dataDir/chord.txt -time -ele 1section 1 deformation;


I would be very grateful if you can answer me as soon as possible.

Thank you in advance.

G.

[vesna]

There is no recorder for chord rotation of nonlinearBeamColumn element. As I explained in my previous post, you need to use two recorders to get cord rotations.

Here is an example:

recorder Element -file basicDef.out -time -ele 1 basicDeformation; #records basic deformations of your element
recorder Node -file nodeRot.out -time -node 1 -dof 3 disp; #records total rotation of node i of your element

Here are the matlab commands that you can use to calculate chord rotation:
nodeRot=load('nodeRot.out');
basicDef=load('basicDef.out');
chordRot = nodeRot(:,2)-basicDef(:,3);

[gersi]

Thank you very much for answering. I have one more doupt about the exact definition of basicDeformation recorder (as I didn't find it in Opensees user manual). In one of your previous posts you said that:

"...With element basicDeformation recorder you can get rotation of node i from the chord (in deformed state of the element) to the tangent of the node (in deformed state of the element). If you are in 2D and you include time in your recorder this basic deformation will be in the third column of the output file. To get chord rotation you have to subtract basic rotation from the total rotation at the node".

I am concerned that the correct definition should be: basicDeformation is the angle between the chord (in the deformed state od the element) and the tangent of the node (in the initial pre-deformed state of the element, and not as you said above "in the deformed state of the element).

I would be very greatful if you could solve this last doupt.

Thank you in advance.

G.

[vesna]

What I sad before is right. Basic deformations are calculated relative to tangent of the node in the deformed state of the element.

[Tas]

I think that both gersi and Vesna mean the same thing.

The angle between the tangent at a node of the deformed shape and the chord between the two ending nodes of the element in the deformed state is equal to the chord rotation at that node of the element.
Basic deformation at an element end is the angle between the tangent of the element at that node in the deformed state and the “chord” (axis) at the un-deformed state.

Is it like that or not?

[Tas]

Dear Vesna,
I’ll put my question in a different (and more clear) way:

gersi said:
“basicDeformation is the angle between the chord (in the deformed state of the element) and the tangent of the node (in the initial pre-deformed state of the element, and not as you said above "in the deformed state of the element)”.
This is equal to the basic deformation (and also to the chord rotation) only at the fixed base of a column where node rotation is zero. In general, this definition corresponds to the drift (as concerns columns) and not to basic deformation.

If I understood well what you are saying Vesna, is that the basic deformation of an element is the angle between the tangent at a node of the deformed shape and the chord between the two ending nodes of the element in the deformed state.
But that is also the definition of the chord rotation too..

So, I believe that the chord rotation is exactly the basic deformation and there is no need to make a subtraction between the node rotation and the basic deformation in order to obtain the chord rotation (if we make such a subtraction at the beam ends then the chord rotation would be equal to zero).

I made simple test (one bay fixed base frame) in which I realized that the chord rotation of the top of the column, that is by default equal to the drift minus the rotation of the ending node, is also equal to the corresponding value of basic deformation! (step10: drift of the column element 1 = 0.0120562 and node rotation of node#2 = 0.00799126. So, the chord rotation = drift - node rotation = 0.0120562-0.00799126=0.0406496. Basic deformation of column 1 at its ending node #2 = 0.0406496. They are equal!)
At the (fixed) base of the column things are more obvious and the basic deformation is any way equal to the chord rotation because the node rotation is zero (basic deformation at the fixed base of column=chord rotation=drift).

Please take a look at the following example and its results.



# 2D Steel Frame Gravity-lateral analysis
# Units Kg,KN,m,sec
file mkdir Steel2D; # create data directory

# First steps of Modeling
model basic -ndm 2 -ndf 3

# Create nodes
node 1 0.0 0.0
node 2 0.0 2.0
node 3 2.0 3.0
node 4 2.0 1.0

fix 1 1 1 1; fix 4 1 1 1

# Mass - Materials - Elements

# Set a parameter for the axial load
set P 180.0;
set g 9.81; # g
set m [expr $P/$g]; # nodal mass

mass 2 $m $m 0
mass 3 $m $m 0

# calculated geometry parameters for Columns
set ACol 0.00538; # cross-sectional area, make stiff
set IzCol 0.000036922; # Column moment of inertia

# calculated geometry parameters for Beam
set ABeam 0.00284841; # cross-sectional area, make stiff
set IzBeam 0.0000194317; # Beam moment of inertia

# material and section parameters
set ColMatTagFlex 2; # assign a tag number to the column flexural behavior
set ColMatTagAxial 3; # assign a tag number to the column axial behavior
set ColSecTag 1; # assign a tag number to the column section tag
set BeamMatTagFlex 5; # assign a tag number to the beam flexural behavior
set BeamSecTag 4; # assign a tag number to the beam section tag
set fc 235000; # Steel Compressive-Tensive Strength (+Tension, -Compression)
set E 210000000; # Steel Young's modulus

# COLUMN section
# calculated stiffness parameters
set EICol [expr $E*$IzCol]; # EI, for moment-curvature relationship
set EACol [expr $E*$ACol]; # EA, for axial-force-strain relationship
set MyCol 86.75; # yield moment
set PhiYCol [expr $MyCol/$EICol]; # yield curvature
set b 0.01 ; # strain-hardening ratio (ratio between post-yield tangent and initial elastic tangent)

# define response diagrams

uniaxialMaterial Steel01 $ColMatTagFlex $MyCol $EICol $b; # bilinear behavior for flexure
uniaxialMaterial Elastic $ColMatTagAxial $EACol; # this is not used as a material, this is an axial-force-strain response
section Aggregator $ColSecTag $ColMatTagAxial P $ColMatTagFlex Mz; # combine axial and flexural behavior into one section (no P-M interaction here)

# define geometric transformation: performs a linear geometric transformation
set ColTransfTag 1; # associate a tag to column transformation
geomTransf Linear $ColTransfTag ;

# element connectivity:
set numIntgrPts 5; # number of integration points for force-based element
element nonlinearBeamColumn 1 1 2 $numIntgrPts $ColSecTag $ColTransfTag; # self-explanatory when using variables
element nonlinearBeamColumn 3 4 3 $numIntgrPts $ColSecTag $ColTransfTag; # self-explanatory when using variables
element elasticBeamColumn 2 2 3 $ABeam $E $IzBeam $ColTransfTag;

# Define RECORDERS -------------------------------------------------------------
recorder Node -file Steel2D/DFree2.out -time -node 2 -dof 1 2 3 disp; # displacements of free nodes
recorder Node -file Steel2D/DFree3.out -time -node 3 -dof 1 2 3 disp; # displacements of free nodes
recorder Node -file Steel2D/RBase1.out -time -node 1 -dof 1 2 3 reaction; # support reaction
recorder Node -file Steel2D/RBase4.out -time -node 4 -dof 1 2 3 reaction; # support reaction
recorder Drift -file Steel2D/Drift2.out -time -iNode 1 -jNode 2 -dof 1 -perpDirn 2 ; # lateral drift
recorder Drift -file Steel2D/Drift3.out -time -iNode 4 -jNode 3 -dof 1 -perpDirn 2 ; # lateral drift
recorder Element -file Steel2D/FCol.out -time -ele 1 localForce; # element forces -- column
recorder Element -file Steel2D/IP.out -time -ele 1 integrationPoints; # location of IP's longwise the element
recorder Element -file Steel2D/Inflcol.out -time -ele 1 inflectionPoint; # inflection Point
recorder Element -file Steel2D/Colsec1.out -time -ele 1 section 1 deformation; # section deformation node i
recorder Element -file Steel2D/Colsec5.out -time -ele 1 section 5 deformation; # section deformation node j
recorder Element -file Steel2D/ColDef.out -time -ele 1 basicDeformation; # element deformation

# Create a Plain load pattern with a Linear TimeSeries
set P 180.0;
timeSeries Linear 1
pattern Plain 1 1 {load 2 [expr $P] [expr -$P] 0.0; load 3 0.0 [expr -$P] 0.0}

# Apply Gravity load
constraints Plain; # how it handles boundary conditions
numberer Plain; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral; # how to store and solve the system of equations in the analysis
test NormDispIncr 1.0e-8 10 ; # determine if convergence has been achieved at the end of an iteration step
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
integrator LoadControl 0.1; # determine the next time step for an analysis
analysis Static; # define type of analysis static or transient
analyze 10; # apply gravity-lateral

[vesna]

Tas, you are right. basicDeformation is equal to the chord rotation.

I wrongly thought that the chord rotation is rotation of the chord between two states of the analysis. I was not familiar with the term. Here at Berkeley we call it basic deformation.