Specifying a base acceleration at a revolute joint.

  • 16 Views
  • Last Post 2 days ago
AndreaEnid posted this 1 weeks ago

Hi! 

I want to assign a base acceleration at the base of a wall that have a rotational base constraint. I used a revolute joint to assing its stiffness. 

The base acceleration allows me to put the base acceleration only at fixed and displacements supports. I will appreciate any help.

 

Order By: Standard | Newest | Votes
peteroznewman posted this 6 days ago

Hello AndreaEnid,

Base acceleration is used to simulate the input a structure might see in an earthquake or when sitting on a vibrating rigid surface like an engine block or a shaker table top.

Can you provide an image of the structure you are working on. I don't understand your "rotational base constraint". Do you mean you have a revolute joint that you added a spring to add rotational stiffness?

Regards,

Peter

AndreaEnid posted this 6 days ago

The wall is the element at the left. The other big element is fixed at the base. The assigned revolute joint at the base of the wall is the one that appears in the tree at the left, below of Connection. I want to put an earthquake at the base of the wall and the other element. ANSYS allows me to put the base acceleration only to the fixed base, but I want to put the acceleration at the base of the wall too. 

AndreaEnid posted this 6 days ago

peteroznewman posted this 6 days ago

Is the yellow wall bonded to the large block?

If so, then just include the bottom of the wall as a Fixed Support. There is such a large mass and a long contact area that the revolute joint on the short edge on the bottom of the wall is going to be insignificant. Suppress the Revolute and add that edge to the Fixed Support.

AndreaEnid posted this 6 days ago

Oh ok. Yes, the yellow wall is bonded to the large block. The problem is that I want to model the wall with a rotational constraint with a stiffness (I have the value), that is a important part of the model. And I need to put the acceleration at the base of the large block (soil) and the wall, but the program allowed me to put it only in the fixed one.

peteroznewman posted this 6 days ago

Create a stand alone Transient Structural analysis system (not connected to Modal) and you can have your rotational joint and spring and apply the earthquake acceleration to all the mass in the model using an acceleration-time history load.

If the wall is supporting a block of soil, I'm not sure that Bonded Contact is appropriate. Wouldn't frictional contact be more appropriate? 

AndreaEnid posted this 2 days ago

I already did that too, but in reality the amplitude of the earthquake is not the same in all the soil. I need to assign the acceleration as a base acceleration.

I am comparing different cases, and one of those cases is considering a Bonded Contact. 

peteroznewman posted this 2 days ago

You could create a third rectangular block under the soil and the wall. Make that a rigid body and use either bonded or frictional contact to the soil. The rotational joint with its mobile side scoped to the base of the wall will now have its reference side scoped to the rigid body. Add a translational joint between the rigid body and ground and add an acceleration load to that new joint. Now you have base acceleration on the soil and the wall.

Close