Element at an angle

[zsherliza]

Hi,

I would appreciate some help in confirming element transformation for my structure. I have modeled a MDOF bridge in 3D (6DOF), and have carefully created nodes to take into consideration the curved portion.
I have also specified geometric transformation for structural elements. The question is, what would the transformation be for elements (local axes) that are oriented at an angle (10 to 30 degrees) to the global axes?

Thank you.

zsherliza
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[vesna]

Your local x is along the element length. The angle of your element does not really matter as you are defining the vector parallel to plane xz (defined by local coordinates x and z). Read more about it here: http://opensees.berkeley.edu/wiki/index ... sformation

[zsherliza]

Dear Vesna,

Thank you for the reply.

[hnsmengyu]

Dear zsherliza ,
I am now doing pushover analysis of bridge and have some problems i want to connect with to for soltions
here is my mail address: hnsmengyu@163.com
Thanks!

[zsherliza]

Dear Vesna,

We all know that ground motions are applied to all nodes using the same record. Since my bridge is curved, some elements are oriented at different angles. I understand why I don't have to worry about element transformation for elements in curved portion, but what about assignment of input motion? I am asking because nodes are created according to the global coordinate. I believe that the assignment of input motion at the curved portion should take orientation of elements into consideration. Is there a rule saying that ground motion should pass the centre of element for analysis purpose? If this is right, how do I assign input motion to nodes which represent the curved portion? OR should I not worry about it?




Thanks Vesna.

[vesna]

When I previously sad that you should not worry about geometric transformation (but you have to define it: e.g., geomTransf Linear 1 0 1 0 (to match local z with global Y where Y was in vertical direction pointing upward)), what I had in mind are deck elements. I do not know what is the shape and orientation of your columns and if it matters for them or not.

If you use uniform excitation pattern for your ground motion you will specify the direction (direction 1 corresponds to global X axis, direction 2 corresponds to global Y axis and direction 3 corresponds to global Z axis) in which the ground motion acts. The ground motion will be assigned in the same direction to all your columns.

[zsherliza]

Vesna,

Thanks for the reply. For your information, I have done all the necessary transformation for elements as you have pointed out here, and I have used the excitation pattern correctly as in the examples (as you have written here as well). I am just wondering about the excitation at the column base on the curved portions, since they are oriented at an angle (angles are different at some nodes), should I take care of this situation?. On the other hand I am thinking that since waves travel at random, I probably do not have to worry about it.

Thank you again.

[vesna]

I would analyze the bridge for different angles of ground motion including all possible angles of columns.