how can i use Nonlinear link in sap2000?

[behzad17533]

I'm surveying the performance of concrete frame strengthened at the joint by FRP laminate and other method by pushover analysis in sap2000, for apply effect of FRP laminate in this analysis we should obtain equivalent additional stiffness that it’s cause FRP.So i modeled all beam column joints in Ansys software and extracted moment-rotation curve(additional stiffness)for all specimens.Now for modeling the FRP retrofitted frame,SAP-2000 nonlinear link elements (NLLink)are used.These elements can simulate the equivalent additional stiffness to the beams provided by web-bonded FRP sheets.I have some problems as below.Your kindly reply will be appreciated in advance.
1-in the define box related Nlink in sap ,what's the “effective stiffness and damping” and ”P-Delta” option? Is it essential to define these parameters?
2-when I define the Nlink with zero length,as same attach picture, should it be double stiffness of the frame elements those which have Nlink elements at their ends (factor of 2 for the moment of inertia of beams,remember parallel or series springs principal)? Is it true? Is it essential to modified of moment inertia?
best regards.
behzad.

 

[saeedjafari]

Dear Behzad
I have the same question. I want to model FRP sheets on web of beams. Please help me, what is your link/support type? How did you assign the dimensions (depth and length) to your link and also other properties. I am in urgent, looking forward to hearing from you.
Kind regards
Saeed

 

[Shz713]

1- You can keep them same, yet it depends on type of analysis you're doing. I did dynamic analysis with no large deformation (p-Delta)

2-I didn't catch this one, but if you put zero length elements then how you expect joints to transfer load effects. Better make very trivial length to avoid numerical instability. Do you want to modify second moment of area (I33) to consider effect of FRP? I would modify the moment/shear stiffness parameters more likely.

There's a report by Caltrans about seismic assessment of bridges. In their report, they extensively shown how to use nonlinear features in SAP2K. If I recall the name of report I will share it.


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