geometric transformation in 3d building model

[setareh20]

Hi,
I have some trouble to define the orientation of my beams and columns. My model is a 3D building in wich X rappresents the longitudinal direction(horizontal), Z rappresent the transverse direction(horizontal) and Y is the height(vertical axis). I use this code:

geomTransf $Coloumn TransfType $IDColoumnTransf 0 0 -1; for the column
geomTransf Linear $IDBeamTransfz 1 0 0; for the beam
geomTransf Linear $IDBeamTransfx 0 0 1; for the beam

Am i doing it right?
Thanks

[vesna]

If you tell me position of your beams in the global coordinate system I can tell you if your transformations are OK.

[setareh20]

Thank u so much for your kind response
In global coordinate system of my building, X direction is from left to right, Y direction is from down to up and Z direction is based on the right hand side rule and the position of my beams are parallel to the X and Z direction.
Wating for ur answer
Tnx

[vesna]

what transformation do you assign for beams parallel to X axis?

[AHARSHIAN]

Hi, I am curious about this question too!

I am defining beams in X direction, Girders in Z direction and columns in Y direction.

geomTransf $ColTransfType $IDColTransf 0 0 1;
geomTransf Linear $IDBeamTransf 0 0 1;
geomTransf Linear $IDGirdTransf 1 0 0;

Are these correct!?

Moreover; There are two examples about 3D Frame building in OpenSees Wiki, My question is regarding the Rectangular Cross - Section file! In that file, there is a sketch of one rectangular RC section which specifies bottom and top of the cross - section! Are those definition for top and bottom of the cross - section, always correct (considering bottom and top reinforcement with above geometric transformation)?

[payamdindar]

setare u must use this code


geomTransf Corotational 1 0 0 -1 ; #colmn
geomTransf Corotational 2 0 0 1 ; #in plane beam
geomTransf Corotational 3 1 0 0 ; #out plane beam

be successfull

[vesna]

AHARSHIAN, your transformation is correct.

I did not understand your other question.

[AHARSHIAN]

Dear Vesna,

Appreciate your answer,
My second question Was about definition of reinforcement fibers in Beam - Column Elements. In example 8, there is one Tcl file which title is BuildRCrectSection.tcl. In that file the rectangular RC cross section is defined and top and bottom fibers for reinforcements are already shown! I was asking if that file could be used for definition of RC sections in any other 3D structure?
But I got my answer and Sorry for replying late.

[shivanirani11]

Dear Aharshian,
I am facing problem in geometrical transformation. So can you please tell me how you have done it. From where you get the details of it. In short, I want to know how to linear transformation will work and how to use this in opensees. Will you help me. I have already refer the mannual for it, I am not able to catch it.

[AHARSHIAN]

Dear Shivanirani11,

I am really sorry I was late since I haven't checked my Postst, If you have not find the answer yet! I could explain it.
I excuse again.

[shivanirani11]

Thanks for reply. I am not find the answer yet. Can you please explain me.

[anonstest]

Hello

I need this same info, could you help us ?

[AHARSHIAN]

Hi,
First have a look at ''http://opensees.berkeley.edu/wiki/index ... sformation''
Now, as you see at the bottom of the page, there is one frame in which columns are defined in GLOBAL Y direction and the only beam is defined in Global X direction.
In all cases (Beams and Columns) you have to know that local x axis is connecting two element nodes.
Now look at element 1 which is Column. The local x axis as I said is in longitudinal direction which is Global Y. If you pay attention, you could easily see that local x and local z axes make a plane (xz plane) in which the local z axis is in NEGATIVE Direction of Global Z axis. Therefore the linear transformation is: 0 0 -1 (X Y Z).
Therefore, For Making Correct Linear Transformation, You Have To Develope correct xz Plane and Then See That Local z is Lying In Which Global Direction (JUST Local z)!

Lets do it for the beam element (element 2):
Local x is in longitudinal direction (connecting two element nodes), local y and local z are following right-hand rule and as you see: In local xz plane, local z axis is lying in Positive Global Y direction. Therefore; the correct linear transformation for element 2 (beam element) is 0 1 0 (X Y Z).

Now, I want to explain it more for Girders:
In 3D Frame building, Girders are like Beams but they are in Global Z direction. Therefore; local x axis is lying in Global Z direction and if you develope a right-hand-rulefor local axes y and z. You will see that one option is to have local y axis in Global Y direction (Negative) and local z axis in Global X direction (Positive). Then again, local z axis is in Positive Global X axis and therefore; correct Linear Transformation would be 1 0 0 (X Y Z).

All I wanted to say is very simple! just make local axes on the element somehow that x local axis is lying on the element length and the other local axes following right-hand-rule. Then look at local z axis and see in which direction it matches to the Global axes (X Y Z). Note: Pay attention to the positive (1) and negative (-1) directions.
If local z axis is in Positive Global X axis: 1 0 0
If local z axis is in Negative Global X axis: -1 0 0
If local z axis is in Positive Global Y axis: 0 1 0
If local z axis is in Negative Global Y axis: 0 -1 0
If local z axis is in Positive Global Z axis: 0 0 1
If local z axis is in Negative Global Z axis: 0 0 -1

Well! The story is finished! Now you could sleep better tonight (Maybe someone posts later and tell me that I was making mistake! Who Knows!?).

[shivanirani11]

Thanks for reply, but as you mention above. You have taken the following geometric Transformation for your 3D model,

geomTransf $ColTransfType $IDColTransf 0 0 1;
geomTransf Linear $IDBeamTransf 0 0 1;
geomTransf Linear $IDGirdTransf 1 0 0;

as column is in y-direction that means in the local x-axis is parallel to global Y-axis. And as per the right hand rule y-axis is along +X-axis and z-axis is along -Z-axis. So transformation should be 0 0 -1. how you get +1.
and in case of beam, x-axis is along +X-axis, and as per RH rule, y-axis is along the -Z -axis and z-axis is along +Y-axis. As per this, the transformation should be 0 1 0,but you have taken as 0 0 1. And this is same as the transformation of column. How the two element in two different directions is having the same transformation.

This is my confusion. Please help me.

[AHARSHIAN]

To Shivanirani11:

It depends on your local axes! Local x axis is always along the length of the element, but other axes could rotate based on right-hand-rule! In my project the orientation of local axes were different from those I have explained for you!
!!local x axis is always fixed BUT other local axes Not!!
You have to first consider one Global Coordinate System and then based on local axes which you "Yourself" consider for the elements (Cross-section), observe the direction of local z axis.
Therefoe; it depends on you! Also, you have to take care regarding definition of fibers in Cross-Section (Top Fibers, Bottom Fibers, ...)