monitoring performance of steel braces

[huffte]

Yes, I see your dilemma Hani. It will be of great benefit to get the maximum post-processing capability out of SeismoStruct.

I think you may be onto something with the links. If you a link with extremely low rotational stiffnesses to connect your braces to the beam-column intersection joint, you should still be able to apply the strain performance criteria and emulate pinned brace connections.

It would seem that your idea is well worth the effort to try Hani.

Keep up the fight. You'll get there.

Perhaps this might also be a good request for future enhancements to the program - the ability to establish performance criteria for inelsastic truss type elements.

[huffte]

Regarding your concrete moment frame, Hani, I believe that your use of the rigid diaphragm constraints in the 2D analysis is unnecessary.

And for the Equal DOF assumption, I don't think that the "ry" degree of freedom needs to be included in the constraint. I assume you are including "x" in the constraint because your assumption is that a concrete slab will force the column tops to move together. This, in itself, may not even be necessary. I think you wil just have to look at the dtails of how the building is constructed and decide if, in fact, the slab will essentially force all nodes at a floor level move together in the x-direction.

In summary, I personally would recommend avoiding the Rigid Diaphragm constraint for the 2D analysis and either use the Equal DOF constraint with "ry" removed, or lose constraints altogether. Note that these constraints will effectively remove any axial load form the beams.

[huffte]

My apologies Hani. The above response to you was inadvertently made to an issue another forum member posed. Please disregard.

[huffte]

Regarding the use of links to model pinned connections at the ends of inelastic elements, I have tried it before and I think it should work.

If you have trouble, let me know and I can make arrangements to get the modified file to you. The link definition, nodes definition, and element connectiity are pasted below. Note that the brlink definition is all one line in the spf file but pastes to 2 lines here.


/&Start of list&/
brlink lin_sym lin_sym lin_sym plst plst plst 9999999 9999999 9999999 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0 1e20
/&End of list&//&Start of list&/
na1 0. 0. 0. structural
nb1 4. 0. 0. structural
na2 0. 0. 3.6 structural
nb2 4. 0. 3.6 structural
ma1 2 0. 1.8 structural
ma2 2. 0. 5.4 structural
na3 0. 0. 7.2 structural
nb3 4. 0. 7.2 structural
ba1 0. 0. 0. structural
ba2 2 0. 1.8 structural
bb1 0. 0. 3.6 structural
bb2 2 0. 1.8 structural
bc1 4 0. 3.6 structural
bc2 2 0. 1.8 structural
bd1 4 0. 0. structural
be1 0. 0. 3.6 structural
be2 2 0. 5.4 structural
bf1 0. 0. 7.2 structural
bf2 2 0. 5.4 structural
bg1 4 0. 7.2 structural
bg2 2 0. 5.4 structural
bh1 4 0. 3.6 structural
/&End of list&/
/&Start of list&/
bracea TRUSS(FRAME) ba1 ba2 nb1
bracec TRUSS(FRAME) bc1 bc2 nb1
braceb TRUSS(FRAME) bb1 bb2 na1
braced TRUSS(FRAME) bd1 ma1 na1
cola1 COLUMNS na1 na2 nb1
colb1 COLUMNS nb1 nb2 na1
beamab1 BEAM na2 nb2 na1
bracee TRUSS(FRAME) be1 be2 nb2
braceg TRUSS(FRAME) bg1 bg2 nb2
bracef TRUSS(FRAME) bf1 bf2 na2
braceh TRUSS(FRAME) bh1 ma2 na2
cola2 COLUMNS na2 na3 nb2
colb2 COLUMNS nb2 nb3 na2
beamab2 BEAM na3 nb3 na1
baconn1 brlink na1 ba1 ba2 nb1
baconn2 brlink ma1 ba2 ba1 nb1
bbconn1 brlink na2 bb1 bb2 na1
bbconn2 brlink ma1 bb2 bb1 na1
bcconn1 brlink nb2 bc1 bc2 nb1
bcconn2 brlink ma1 bc2 bc1 nb1
bdconn1 brlink nb1 bd1 ma1 na1
beconn1 brlink na2 be1 ma2 nb2
beconn2 brlink ma2 be2 be1 nb2
bfconn1 brlink na3 bf1 bf2 na2
bfconn2 brlink ma2 bf2 bf1 na2
bgconn1 brlink nb3 bg1 bg2 nb2
bgconn2 brlink ma2 bg2 bg1 nb2
bhconn1 brlink nb2 bh1 ma2 na2
/&End of list&/

[hani.akkari]

Dear Huffte,

first i want really to thank you for the precious support and effort that you are providing to me. i made a small model with the link elements as per your instructions (i made a 1 bay, 1 storey model for the seek of trial, before generalising to greater model). i m having an error message (attached and the model can't proceed. i attached to you a hand sketch for the model data, the error message and the model. i really appreciate if you can have a look on it and inform me where is my mistake.

hand sketch
https://dl.dropbox.com/u/33925535/Model%20Data.pdf

error message
https://dl.dropbox.com/u/33925535/error%20message.JPG

model
https://dl.dropbox.com/u/33925535/MODELINK.spf

again thanks a lot Huffte.

Regards,

[huffte]

Hani,

I think you should try adding restraints for x-rotation and z-rotation at your column bases since you are doing a 2D analysis.

And you should also restrain all other non-support nodes restraints for y-translation, x-rotation, and z-rotation.

I added these restraints and the model ran.

[hani.akkari]

Dear Huffte,

thanks a lot , it's working . i will go through results and comeback to you in case of any problem that i may not be able to solve. again thanks a lot fo ur continuous help.
regards,

Hani