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

deflections/stress due to self weight

754 Views, 5 Replies
04-20-2012 07:19 AM

hello

suppose there is a large beam say 80 ft cantilivered beam rectangular c/s.

so asim doesnt output results beacuse of the loading caused only by self weight right?

ASIMM 2012
Employee
Posts: 492
Registered: ‎03-25-2010

Re: deflections/stress due to self weight

Wrong. The beam has weight, and causes stress and displacement, if the material properties include the mass density and gravity ti turned on.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
Distinguished Contributor
Posts: 108
Registered: ‎03-16-2012

Re: deflections/stress due to self weight

wow...I somehow thought that gravitaional force will be added.....we need to turn it on.....thats why i see less stress values......thanks john...

ASIMM 2012
Distinguished Contributor
Posts: 108
Registered: ‎03-16-2012

Re: deflections/stress due to self weight

04-20-2012 08:58 AM in reply to: INACTIVE_AstroJohn

John one more question

Say I got a same cantilevered rectangular c/s beam solid meshed say with tet elements.

say side A is fixed and side B is free.

suppose on the top of side B of the cantileverd ,solid meshed beam, i would create a beam element ( yes i will create X to avoid balljoint) and give rectangular section properties.Its a dummy element and I want to give a mass property of my own, not the one calculated by software.Is there an accepted way to this?

What I did was, make the density of the Beam element Zero   and add a distributed load value of my required weight.

I did that and I see some weird number in the weight of the overall structure.So I am wondering if there is an accepted way to do that?

ASIMM 2012
Employee
Posts: 492
Registered: ‎03-25-2010

Re: deflections/stress due to self weight

Hi,

I do not know how you are getting the weight of the overall structure ("I see some weird number in the weight"), but a distributed load is obviously not a weight. So if you are using the "Analysis > Analysis > Weight and Center of Gravity", the calculated weight will not include the "weight" that you simulated using the distributed load.

If you sum the reaction forces in the vertical direction, they should equal the weight of the solid elements plus the distributed load applied to the beam elements.

The other way to add weight to a model is with the "Setup > Loads > Weight" command.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
Distinguished Contributor
Posts: 108
Registered: ‎03-16-2012

Re: deflections/stress due to self weight

04-20-2012 12:01 PM in reply to: INACTIVE_AstroJohn

yes you are right...

I theroized that distributed load in global Z direction as weight of the part if you can change the value of density of the part to zero ...obvisouly you can get that as reaction force....