Geometrical Transformation

[rmandok]

Hi
One of my colleagues told me that opensees won't consider the effects of P-Delta (major and minus) unless you define a little eccentricity in the middle of the column (He claims that he built some models and then came to this conclusion). Now i want to know is it really true that if we define our geomTransf, Corotational the program won't consider the effect of P-Deltas until we define a eccentricity for the column or not?!

[AHARSHIAN]

Hi,

I think he is not completely right! Three things in OpenSees for Geometrical Transformation:

1) P-Delta (major) which is based on end nodes relative displacements can be included in your model with PDelta Geometric Transformation Option.
2) for P-delta (minus) which is based on relative displacement to the chord, there is no option in OpenSees! But remember that you can simply devide your element to some sub-elements and apply P-Delta! In this case you are including both P-delta (minus) and P-Delta(major). It is like a trick! but it really works well.
3) Corotational Geometric Transformation Option works for large displacements-small strain problems but unfortunately it neglects elemental loads! So, if you have some frame elements with loads on them, this geometric transformation object is useless!

I think P-Delta is enough for typicall structural problems, if you have large deformations (high order of geometrical nonlinearity problem), just break your elements to some finer elements and again use P-Delta!

[rmandok]

Thank you for your effective help dear Arshian

[vijaykulhar]

I have doubt in "geomTransf Linear" command definition. Please tell me how to define this command
You can see this pitcher here http://kulharvijay.wordpress.com/?attachment_id=244
As shown in figure how to define geomTransf Linear command for Element 5-9 OR 6-9 etc.

[rmandok]

Dear Vijaykulhar, Here is a file that contains 3D frame figure and the OpenSees code. you can download this file from here:
http://www.filedropper.com/3d_1
I hope that it helps.

[vijaykulhar]

Thanks Dear rmandok ............ but i am not able to download this file .....may be because of different country location ........
I will be very thankful to you if could Email this file me @ kulhar.vijay@gmail.com
Hoping a positive reply...........
Thanks a lot sir

[rmandok]

Dear Arshian
Can you please explain more about corotational geomtransf? so if it is better to use p-delta what is the purpose of using corotational?!

[AHARSHIAN]

Hi rmandok,

For the case that you have beam-column elements WITH LOADS on them, the corotational geometric transformation is useless because it neglects the elemental loads! Then you can apply P-Delta but for considering large deformations you have to break your element into some sub-elements and apply P-Delta. This method considers both P-Delta and P-delta!

I think, Corotational Geometric Transformation can be applied for the cases in which you apply deformations to your structure and there is no load on the elements!

[vijaykulhar]

for recording data we use command like this
recorder Node -file $dataDir/DFree.out -time -node 4 -dof 1 2 3 disp; # displacements of free node
this records data in .out file.
Now my question is that can we change this .out file to .xlsx (i.e. excel) directly ??

Thanking you

[vesna]

Try it. It may work.