topic Re: deflections/stress due to self weight in Simulation Mechanical Forums (Read-Only)

deflections/stress due to self weight

Anonymous — Fri, 20 Apr 2012 14:24:42 GMT

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?

Re: deflections/stress due to self weight

John_Holtz — Fri, 20 Apr 2012 15:14:29 GMT

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

Re: deflections/stress due to self weight

Anonymous — Fri, 20 Apr 2012 15:30:54 GMT

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...

Re: deflections/stress due to self weight

Anonymous — Fri, 20 Apr 2012 15:58:34 GMT

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?

Re: deflections/stress due to self weight

John_Holtz — Fri, 20 Apr 2012 18:31:43 GMT

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.

Re: deflections/stress due to self weight

Anonymous — Fri, 20 Apr 2012 19:01:19 GMT

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....