*Foundation, help understanding

[GustavLund]

Hi.

I'm thinking about using *Foundation in my model. I'm using shell element STRI3. After reading in the Abq manual it is my understanding that using this card means putting my elements on "a bed of spring". The element are located exactly in the x-y plane. Let say that I apply *Foundation on SNEG of the elements and then apply a load (in z-direction) on the SPOS pointing IN towards the element. The shell body is encastre at the boundaries. I'm guessing that the foundation will now affect the deflection of the body. The deflection will be smaller than if *Foundation was'nt used.

If I apply the force in the other direction, acting on the SPOS but going OUT from the body, will the *Foundation still affect the deflection, now going in the other direction? Will the absolut values of the deflection be the exact same number? I.e. are the "springs" attached to the elements, or do they only rest on them? Does it matter on which side I apply *Foundation?

 

[burningDiesel]

It won't matter, the foundation is very similar to just using *spring , it is more convenient because you can assign it to element sets instead of discrete nodes, and it scales to the element surface. So, like a linear spring, it will act in both ways.
Actually in CAE, I don't know why you have to select a surface and side, because the *foundation keyword works with element sets.

 

[GustavLund]

Ok, thanks! Regarding chosing side, I realized that Foundation was applied to an element set. I had name the set in such stupid way that when looking at the model after som time I thought it was a surface...

So, the foundation is attached to the elements, giving stiffness regardless if deflection is going down in towards the foundation or up from the foundation?