Friction Pendulum Isolators

[huffte]

As noted by the SeismoSoft team, the fixed base moves with the ground. In my experience, the best way to get isolator device displacements is to observe link hysteretic curves in the post-processor. So it may be that you are doing nothing wrong. I would recommend some quick hand calculations to estimate isolator displacements and see if the results make sense. SeismoStruct, in my experience, is super at this type of analysis. Best of luck.

[Zsediqi]

thank you so much for the clarifications.

[Zsediqi]

Hello,
I performed an incremental dynamic analysis (ground motions are applied on x, y, z directions) on a base isolated building (with 16 friction pendulum isolators), when i checked the link hysteritic loop (D1-F1, D2-F2) it doesn't not look like a loop of a base isolator, the loop is not smooth And is very unsymmetric, the K1 and k2 parts of the loop can not be recognized(no straight line for K1 and k2 in the loop).
What can be the mistake? How can I solve this problem?
If further detail is needed I can send the hysteretic curves through email.
Thank you for your time and support.

[huffte]

If I recall correctly, the DOF 1 is axial force in the link element. DOF 2 and DOF 3 are the translational degrees of freedom in the link. Which type of link element are you using? plst maybe? In addition to making certain your link element setup is correct and plotting the appropriate DOF hysteresis, I would recommend double-checking the loading specification (for example, if the input accelerations are in units of "g", you may have to multiply by 981, or some other appropriate value depending on specified units) to specify the loading properly.

Best of luck, Zsediqi.

[Zsediqi]

Thank you for your replying, you are right D1-F1 is for axial force.
I am using isolator2 element. i am multiplying the input GMRs by 9.81 since the acceleration units are in "g", (Peer ground motion format) .
The D1-F1 hysteretic curves seems linear with very small disps but The D2-F2, D3-F3 hysteretic curves are very unsymmetric and not smooth as I mentioned before.

[üzeyir]

hello,
i modeled a ten story base isolated building with friction pendulum base isolators using building modeller (.bmf) . the project is created and the friction pendulum isolators are placed directly at isolator2 (.spf file) which represents the friction pensulum isolators. in addition to isolator2, do we need to add links? for exp: linlink, NLlink ? or only isolator2 is enough. if link element is needed than which type of curve is appropriate for FPS, plst, bl_kin etc.
thank you for your time