Why the section of element is twisting pier when there is an eccentricity in global X & Y direction (top and bottom nodes)?

Question:

Dear Midas,

Firstly, I have ask the same question of the topic but have not yet get a satisfying answer from the local representative in Indonesia. The problem is when I modeling an element which have an eccentricity in both global X & Y direction (top and bottom nodes), the element is twisting, even I already set the Beta Angle = 0. Why that is happen? it is just a graphic issues or not?

Please find attach file for detail model regarding the question.

Answer:

Hello,

Thanks for showing interest in midas Civil!
Actually 2 basic rules are followed when generating a line beam element.
1)  Local x axis would be along the line connecting the 2 nodes
2)  Local z axis would be parallel to the line connecting the 2 nodes when viewed in plan.
With these rules, lets have a look at plan of a model with rectangular column of different orientations.
These rules are true for any FE model, since there is no other way to judge the z axis orientation.  Hope this clarifies your doubt.  Kindly let us know if further assistance would be required.

Regards,
Nandeep
Technical Manager, MIDAS


Dear Nandeep,

Thanks for the reply and the explanation regarding my question.
So, if I want to model a line beam element with larger different global X & Y between top and bottom nodes and want the section to be perpendicular to X-Y (means no twisting), what is the best way?
  1. Model the line beam element with set of beta angel corresponding the eccentricity between top & bottom nodes? or
  2. Model the line beam element by "Create an Eccentric Elements"?
and, if the two methods above have the same behavior? especially the way of MIDAS software analyze the model in no.2

Best Regards



Hello,

The correct way to go about this would be method 1.  In fact, method 2 wouldn't be giving results as expected.
Hope this helps.  Kindly let us know if further assistance would be required.

Regards,
Nandeep
Technical Manager, MIDAS
Creation date: 10/17/2018 9:10 PM (dklee@midasit.com)      Updated: 10/18/2018 6:41 AM (dklee@midasit.com)
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