Learning Forum

[sameerfares]

Hello All,

What is the difference in "Joints Revolute-Ground to Multiple" behavior between selecting two faces shown in green below for the scope versus using the top two edges of the two angles?Is Revolute-Ground to Multiple supposed to be assigned to edges not faces?

Regards,

Sam

[peteroznewman]

It's better to select the faces for the joint because the faces cover an area and a spider of Connection Elements (CEs) can be drawn from the nodes on those faces to the point at the centroid of the faces that was created for the joint.

The problem with selecting just the top edges is that all the nodes are in a straight line. This is a problem because the revolute joint has to support moments and there are no nodes off the line of the top edge with which to apply a force to generate a moment. This would cause a mathematical problem called ill-conditioning.

If you click on the Reference Coordinate System for the joint, then I could see what direction the local Z axis of the joint is pointing. I hope you know.

Regards,
Peter

[sameerfares]

Hi Peter, below is a joist seat sitting on a beam. Seat angles  is welded to to beam with 1" long fillet weld on near and far sides. this is considered a pinned connection. What is the best way to model it in Mechanical? is there a way to model it with using welds? Thanks!

[peteroznewman]

Hi Sam,

If the beam is modeled using solid or shell elements (not beam elements on a line body), then you can either create small triangular bodies to do bonded contact through weld fillets, or if you want a less detailed model, you can just do bonded contact from the thin edge faces of the angle brackets to the face of the beam flange, assuming the angle brackets are solid bodies. The angle brackets could be sheet bodies, then the bonded contact would be from the edge to the flange face of the beam.

I suppose it is called a pinned connection in the industry because the flange can bend and provide some flexibility.

Regards,
Peter