link element

[khajehdehia]

Hi
I have modeled one shear wall at the x-z plane I want the Wall remains elastic and I have used one link(isolator) as the support and another link at the top of Wall as the connection element. I want the links get inelastic and the wall remains at the elastic range.
I analyses the structure by nonlinear dynamic time history . I want to know whether I must apply the the time history load at the top link or not because when I apply the load only at the support link the top link is separated from the top nods and the behavior of wall and the relative top displacement curve are unusual moreover I have another question as you know to define the link element we use two nod If I must restrain all degree of freedoms of one nods of link at the top link like support link or not

tanks alot

[huffte]

khajehdehia,

It is unclear why you need a link at the top of the wall. Is the top link connecting a frame to the wall? And you description makes it a bit difficult to answer the questions you have posed.

Normally, one might connect the bottom of the isolator rigidly to a base node using constraints or elastic elements with the appropriate stiffness. The base node would then be the node to which the acceleration time history is applied, not the isolator node.

You might benefit further from a forum search on "isolator" or "bilinear link" . . . . .

Best of luck with your work khajehdehia.

[khajehdehia]

Dear huffle
the top link is used as a connecting element to the beam but I don't model the beam I just model the top link therefore I define two coincident nod in one nod I define the stiffness and in another nod I restrain the degrees of freedoms like the support links so I apply the time history nod at the restrained link now I want to know If I must apply the time history load at the top restrained nod or not ?

[seismosoft]

If your intention is to model the response of a wall subjected to seismic action, then the time-history load needs to be applied at the base alone, since that is indeed where earthquakes hit a structure.

Your decision to introduce, at the top of the structure, a link element connected to the ground does seem peculiar to us, and it is something that we definitely would not recommend.

Seismosoft Support

[khajehdehia]

how can I model the top link as a top energy dissipating device so that I dont want to model the top beam . I saw the model in the sap2000 program , the top link is modeled so that it connects to the fixed support in one side and connects to the shear wall in another side we want the wall subjected to the earthquake load remains at elastic range but the energy dissipating devices reach the inelastic region

[huffte]

Can you tell me to which SAP2000 model you are referring? Is it an example in the SAP2000 manual? Perhaps if I can see the model I will have a clearer idea of your problem.

[khajehdehia]

sorry I was on holiday i will send you the model but the problem was solved since my teacher said that the sap2000 model is not the true modelling