Working with a gravity load and objects with mass

[mcook21VD9DL]

Hi there,

If anyone could make this more clear to me it would be fantastic.

Let's say I have an object sitting on a tower and it is connected at 4 points directly above 4 pillars. I understand that if I apply a gravity load to my model, my beams will be under their own weight, which is ideal.

However, normally I would just turn my object masses into forces/pressures and apply them as I see fit. I've never used a concentrated mass before. Instead of having a 3 ton object applied as a 29.4kN load central to the beam it's on, could it possibly be more accurate to apply it as a mass and let a global gravity load imply gravity onto the mass which would basically give the 29.4kN? Assuming everything is dead central.

Cheers

[John_Holtz · Accepted solution]

If everything is equal in the two models (one model with forces/pressure, second model with concentrated mass), the results will be the same.

One thing that may make a different in some models is if you use a rigid connector to attach multiple columns  to one mass. Naturally, the rigid connector adds rigidity to the structure which the forces/pressure applied to the columns would not have.

The other advantages to using masses are things like this:

• If you do a modal analysis (Normal Modes) or any of the vibration analyses, you will want to use the mass.
• If you have an analysis where the device is held in different orientations, what you would do is use the same model and change the direction of gravity. It is easier to change the direction of one load (gravity) than multiple force/pressure loads.