questions about rigid link

[baozai]

Hi, All, I met a problem. I establish a rigidlink Beam in opensees, node 1 is master node and node 2 is slave node, and equalDOF "x and y disp" of another node (node 3) to node 2. But the output show that the displacement of this node 2 and node 3 (with equalDOF commands) is different?

[vesna]

What constraint handler did you use?

[kitefall]

in the rigid link command,beam means both the translational and rotational degrees of freedom are constrained.However,in the equalDOF command, the constrained is owe to what the $dof that you choosed.if you choose 1 3 (in the 2 ndm 3 ndf),the result of both that two command will be same.

[baozai]

I used rigid link beam and use equalDOF to make the contact point move the same as the rigidlink end. but I found that the vertical displacement of these two nodes are different. If I used an elastic beam with big stiffness instead, the node displacement are the same.

[paperairplane]

baozai wrote:
> I used rigid link beam and use equalDOF to make the contact point move the
> same as the rigidlink end. but I found that the vertical displacement of
> these two nodes are different. If I used an elastic beam with big stiffness
> instead, the node displacement are the same.

hi baozai, i pretend to bulid a modle of prestressed concrete beam.but i
still cannot solve the problem of rigid beam,which make concrete and bar work together .
"an elastic beam with big stiffness"really help me ,thanks!

[isolator]

@baozai
"an elastic beam with big stiffness",is using "element elasticBeamColumn"this command,and E is at least 100 times concrete's E ,is it right?

[vesna]

yes, you are right, although multiplying by 100 is maybe too much. if this does not create convergence problem it is ok. if it creates convergence problems you can reduce it up to 10.

[isolator]

THanks!