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Element Orientation Vector
2

Element Orientation Vector

Element Orientation Vector

(OP)
I just started using NEiNastran v9.02 recently and for practice, i am modeling basic line models (steel beam structure for example).

When I mesh each line (or curve), I designate the material, beam cross section, and then it asks for the element orientation vector. I presume this is to identify the major and minor axis of the cross section.

However, when I have a beam that is not horizontal or vertical, obtaining the correct element orientation vector is perplexing. Is this step crucial in calculating the global stiffness of my structure? For now, I designate a unit vector in the x, y, or z axis that is not collinear to the beam's length. Thanks for the help...

RE: Element Orientation Vector

Your presumption is correct.  The orientation vector is critical unless the beam cross-section properties do not vary with orientation, e.g., a circular section.  Have you read the user's manual re beam element definition?

RE: Element Orientation Vector

(OP)
I have read that part but it is no help, unless I am reading the wrong one. Do you know of a better reference source than the one NEiNastran supplied? Thanks!

RE: Element Orientation Vector

The figures in the CBEAM and PBEAM sections of the NEi Reference Manual are fairly clear.  See also the Bar Element section in the NEiModeler (Femap) Users Guide.

RE: Element Orientation Vector

Try switching on the beam orientation vector in the display menu of your preprocessor. It'll make things slightly more clear.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Element Orientation Vector

(OP)
Thanks! Those references helped my understanding a little more. Also the visualization of the orientation vector was helpful.

RE: Element Orientation Vector

kacstic,

How about giving them a "purple star".  In the lower left hand corner of all posts is a purple star and a "Thank ______ for this valuable post".  Click on that for each person that gave you a valuable post and they get a vote for "Tipmaster of the week".

Thanks!

RE: Element Orientation Vector

Hi I have a similar question to the one discussed here.

I am trying to mesh a line (set of curves) that uses all three golbal planes with beam elements.  Is there a way I can make the element orientation vector to be always perpendicular to the direction of the curve, rather than being relative to the global coordinate system?

At the moment I get errors as at some points since the "element orientation is colinear with element x-axis".  I do not want to define a random out of plane vector as the element orientation is important to the analysis.

RE: Element Orientation Vector

I think you need to tell us which preprocessor you are using. At least in God's preprocessor this is fairly easy, Hypermesh, not so much. Clue: a vector can be very long.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Element Orientation Vector

Oh sorry, yes that would help.  Am using FEMAP

RE: Element Orientation Vector

Good choice - So just set a node a long way from your structure and use that as your reference vector

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Element Orientation Vector

Thanks, will give that a go

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