Discussion Groups

Simulation Mechanical and Multiphysics

Reply
Distinguished Contributor
madg1
Posts: 108
Registered: ‎03-16-2012

Beam offsets and model rotation

241 Views, 5 Replies
11-02-2012 07:41 AM

Hello all

 

i need your help reg application beam offsets.

Suppose you have a simple truss like structure with beam elements and beam elements got offsets.

 

As we can offset beam elements only in global coordinate system (as we cannot offset in memeber local coordiante system),  what would be simple way to model the offsets? Inputting 3d coodinates for a fairly large structure would be tedious.

 

And if i want to rotate the model, do these offsets in the intial position carry on to the new position.

 

thanks for your help.

madg1
ASIMM 2012
Please use plain text.
Valued Mentor
AstroJohnPE
Posts: 504
Registered: ‎08-30-2012

Re: Beam offsets and model rotation

11-05-2012 08:34 AM in reply to: madg1

Hi.

 

My guess is that the beam offset entries do not "rotate" if you rotate the model. They are probably just numerical inputs and will not update regardless of what geometry manipulations are performed.

 

Beam offsets are a mathematical way to model an offset. The other way is to model the offset using short, stiff beam segments to connect the ends of the offset member to the structure. I have attached an image showing what the model would look like for a stiffener on the side of a tank.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Distinguished Contributor
madg1
Posts: 108
Registered: ‎03-16-2012

Re: Beam offsets and model rotation

11-05-2012 08:38 AM in reply to: AstroJohnPE

so john you mentioned plate to beam...

to be specific in my problem...it will be beam to beam which i think the offset theory would be the same...

in the image you provided....."beam connected to plate with "rigid", you mean rigid elements right?

madg1
ASIMM 2012
Please use plain text.
Valued Mentor
AstroJohnPE
Posts: 504
Registered: ‎08-30-2012

Re: Beam offsets and model rotation

11-06-2012 08:35 AM in reply to: madg1

Rigid elements are usually a pain to work with because of some strange requirements. I think it is just as easy to use a beam element. These could be on a new part number to make it easy to hide, or different layer number. The cross-sectional properties probably need to be roughly 1000 times larger than the real properties. After the analysis, check the properties to make sure they stiff enough (the same rotation angle on each end of the beam).

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Distinguished Contributor
madg1
Posts: 108
Registered: ‎03-16-2012

Re: Beam offsets and model rotation

11-06-2012 08:37 AM in reply to: AstroJohnPE

you are late john.....:smileysad:

 

i already used rigid elements......one element per offset and i just got 400 parts just for the offsets....:smileysad: 

 

 

madg1
ASIMM 2012
Please use plain text.
Distinguished Contributor
madg1
Posts: 108
Registered: ‎03-16-2012

Re: Beam offsets and model rotation

11-08-2012 05:49 AM in reply to: AstroJohnPE

Hello john

 

i used the same method as you mentioned.

i used beam elements as offsets with very high c/s properties.

you mentioned about the rotation angle.you mean same rotaton angle on each end of the beam right?

 

 

madg1
ASIMM 2012
Please use plain text.