Period Difference between SAP and OPENSEES

[silvia]

i don'tknow. someting is up iwth your stiffness.

[jwieser]

Hello basir,

I too am modeling the SAC building except I am modeling the entire building in 3-D. I also am having difficulty matching the period with my SAP models, however your period match significantly better than mine in the elastic case.

I was wondering if you were modeling any pin ended beam connections. And if so with what command were you doing so in OpenSEES.

Also if you have any advice in modeling these building I would greatly appreciate it.

Thanks

[basir]

hi dr silvia
i solved all my problems
and i wanted to thank you
you helped me so much
tanx again

[silvia]

what was the problem?

[basir]

hi jwieser
first of all i suggest you to read examples very carefully lots of your problem solve there.
anyway i used pinned conection in sac 20 and also i used simple connection for base connection of sac 9 and sac20
you can use ''equalDOF'' comand to do that
first read the manual but this is the example
if you have one story one bay structure this would be the procedure:

node 1 0 0
node 2 0 2
node 20 0 2
node 3 2 2
node 30 2 2
node 4 2 0
element elasticBeamColumn 1 1 2 $A $E $Iz $transfTag
element elasticBeamColumn 1 20 30 $A $E $Iz $transfTag
element elasticBeamColumn 1 4 3 $A $E $Iz $transfTag
equalDOF 2 20 1 2
equalDOF 3 30 1 2

you can use any sort of elements here
also use 'constratin transformation' for analysis

and yes difrent program result in diffrent answers but i think
its better to check it with elastic beam column element
and be care full about fiber sections
fiber section where my mistake and when i just correct that i got reasonable responses

if you would like you cand send your model to me by saturdy and i will check it

[basir]

dear dr silvia
it was really silly
i used box section in my model and used fiber section to model that but i didnt notice to the sequence of entering the i j k l vertexes of ''Quadrilateral Patch Command''.
but finally i found the mistake
tanx again dr

[silvia]

ouchy, that's a tough one.
i recommend you first do a moment-curvature analysis on all your sections -- easy to say now.

[basir]

[quote="silvia"]ouchy, that's a tough one.
i recommend you first do a moment-curvature analysis on all your sections -- easy to say now.[/quote]

yes
but i really didnt think of that at all
i found it by chance but this mistake compelled me to read and try more an more and learn alot during this investigation dr silvia
by the way is there anyway too export result directly from recorder to the 'microsoft excell '

[silvia]

i have to say that opensees makes you learn a lot about what you are doing.


don't use excel, use matlab for data processing.

otherwise, you can just write macros in excel, but that's crazy!
you can do some of the postprocessing in tcl, too.

[basir]

of course opensees is a good teacher dr
i will be back very soon with lots of other questions
best regards

[andrewfirst]

Hi, basir
I've encountered similar problems now.
Have you resolved them?

[walaycow]

I have also encountered the same problems while working on this for my roomate, still searching for ways around.

[Amirsardar13]

In your opinion, Is 10-20 percent different in periods gotten from SAP2000 and OpenSees reasonable? Note: Periods in SAP are larger.

[GeoCham]

I've got the same problem with my model too, I just posted a new thread about it.