EqualDOF more than two nodes

[pkm]

hello,
I have problem with equalDof 3 nodes!!
equalDOF 71 72 1 2;
equalDOF 7 71 1 2;
equalDOF 7 72 1 2;
IN this way When i check displacements in x , y direction node 72 has different displacment! about 10 times bigger than node 71,7!?!!
but when i change it by 4node that one is masternode and others are slaved , displacements are the same.
equalDOF 7 71 1 2;
equalDOF 7 72 1 2;
equalDOF 7 73 1 2;
why ??
please help me, i'm confused!!

[vesna]

Do nodes 7, 72, 71, and 73 all have the same coordinates? What constraints do you use?

[pkm]

yes, the coordinates are same in all nodes. I equalDOF them in Dx, Dy. in fact this node are part of my code in the end of my brace.
nodes 71 and 72 are rotating as a friction damper. and i want to pin the brace to them. in otherwords, brace is connecting pinned to 2 element that are connecting frictionary, here is my part of code: (In this code i have used 4 nodes with same coordinates)
node 1 0.0 0.0
node 2 400.0 0.0
node 3 0.0 300.0
node 4 400.0 300.0
node 5 310.0 300.0
node 51 310.0 290.0
node 52 310.0 290.0
node 6 400.0 210.0
node 61 390.0 210.0
node 62 390.0 210.0
node 7 350.0 250.0
node 71 350.0 250.0
node 72 350.0 250.0
node 73 350.0 250.0

node 8 173.0 127.67 # brace midpoint
node 9 5.0 3.75
node 10 6.0 4.5
#=====================

# Boundary Condition
fix 1 1 1 1;
fix 2 1 1 1;

# EqualDOF
equalDOF 51 52 1 2
equalDOF 61 62 1 2
equalDOF 7 71 1 2
equalDOF 7 72 1 2
equalDOF 7 73 1 2

element nonlinearBeamColumn 13 1 3 10 024 2
element nonlinearBeamColumn 26 2 6 10 024 2
element nonlinearBeamColumn 64 6 4 10 024 2

# Beam
element nonlinearBeamColumn 35 3 5 10 3 1
element nonlinearBeamColumn 54 5 4 10 3 1

# Knee Elements
#element nonlinearBeamColumn $eleTag $iNode $jNode $numIntgrPts $secTag $transfTag
element nonlinearBeamColumn 551 5 51 10 012 1
element nonlinearBeamColumn 7152 71 52 10 0122 3

element nonlinearBeamColumn 661 6 61 10 012 1
element nonlinearBeamColumn 7262 72 62 10 0122 3


# Brace Element

element elasticBeamColumn 19 1 9 13.2 2E11 318 1 # rigid Offset - Column side
element dispBeamColumn 910 9 10 5 01 1 # Gusset Plate
element dispBeamColumn 108 10 8 5 012 1
element dispBeamColumn 873 8 73 5 012 1


element zeroLength 5152 51 52 -mat 22 -dir 6 #friction
element zeroLength 6162 61 62 -mat 22 -dir 6 #friction
element zeroLength 7172 71 72 -mat 22 -dir 6 #friction

element zeroLength 771 7 71 -mat 1 -dir 6
element zeroLength 772 7 72 -mat 1 -dir 6
element zeroLength 773 7 73 -mat 1 -dir 6

Is this way rigth??

[vesna]

Would you draw a sketch for me so I can visualize what is that you are trying to model?

[pkm]

Dear vesna,
Sketching here is difficult, so I have send tcl file for you.
thanks.

[vesna]

Yes, you can model it that way but make sure that with the three rotational springs 773, 772, and 773, you are modeling what you intended to model. If you want you can also model it with a two springs 771 and 772. Just remove node 73 and connect your brace to node 7. In that case you will need only these two constraints:
equalDOF 7 71 1 2
equalDOF 7 72 1 2

Also, I noticed that you are using dispBeamColumn elements for your braces. In that case I would use more than two elements for brace to get more realistic results. If you want to use only two elements, forceBeamColumn element would be more appropriate.

[pkm]

I have tried this(equalDOF 7 71 1 2 and equalDOF 7 72 1 2) . but when i checked nodes displacements it was strange!! node 7 and 71 had same displacement but node 72 had different!! about 10 times more than 7 and 71 displacement!!??

[vesna]

This is strange. I just tested the code you sent me without node 73 and I am getting identical displacements at nodes 71 and 72.

[pkm]

vesna wrote:
> This is strange. I just tested the code you sent me without node 73 and I
> am getting identical displacements at nodes 71 and 72.

Really!!! would you please send me your changed code?
Maybe i got wrong?
Maybe there is a problem with my pc!!?I'm confused
thanks

[vesna]

What is your e-mail?