Seismic performance of steel moment frames with variable friction pendulum systems under real ground motions

Abstract

Many researchers have already acknowledged that the base isolation system as the most feasible and economical method for civil engineering structures exposed to the seismic excitation. The Friction Pendulum Systems (FPS) have steel concave surface connected with articulated friction slider and utilized the concept of pendulum for lengthening the period of the superstructure so as to dissipate the seismic energy. The present study investigates on various design approaches for the evaluation of the seismic response of steel frames equipped with FPS. The response of isolated frames is simply adjusted by several parameters such as the friction coefficient (μ), the radius of curvature (R), the isolation period (T) and the axial load and so 2D, three bay 3 and 7-storey steel moment resisting frames (SMRF) are designated as isolated frames in order to examine the effect of variation of the R and the friction coefficient on the seismic response of the isolated frames. The R and μ are predefined as 1, 1.55, 2.25 and 0.025, 0.05, 0.1, respectively. The seismic response of the modelled isolation systems has been evaluated through nonlinear time history analyses, a set of ground motions using SAP2000 software. The local and global deformations are employed to compare the seismic performance of different isolation frames through nonlinear analysis. The results showed that the isolated frames having greatest radius of curvature with lowest friction coefficient exhibited better seismic performance than other models in terms of the local and global deformations.

Keywords

• Friction pendulum systems,Isolator response model,Seismic isolation,Time history analysis

References

1. 1. Matsagar, V.A., and R.S., Jangid, Influence of isolator characteristics on the response of base-isolated structures. Engineering Structures, 2004. 266: p. 1735-49.
2. 2. Xu, C., J.G. Chase, and G.W. Rodgers, Physical parameter identification of nonlinear base-isolated buildings using seismic response data. Computers and Structures, 2014. 145: p. 47-57.
3. 3. Alhan, C. and S. Öncü-Davas, Performance limits of seismically isolated buildings under near-field earthquakes. Engineering Structures, 2016. 116: p. 83-94.
4. 4. Cancellara, D. and F.D., Angelis, Assessment and dynamic nonlinear analysis of different base isolation systems for a multi-storey RC building irregular in plan. Computers and Structures, 2017. 180: p. 74-88.
5. 5. Naeim, F. and J.M. Kelly. 1999, Design of Seismic Isolated Structures. John Wiley & Sons, New York, NY, USA, 1st edition.
6. 6. Bhuiyan, A.VR., Y., Okui, H., Mitamura, and, T., Imai, A rheology model of high damping rubber bearings for seismic analysis: Identification of nonlinear viscosity, International Journal of Solids and Structures, 2009. 46: 1778–1792.
7. 7. Landi, L., G. Grazi, P.P., Diotallevi, Comparison of different models for friction pendulum isolators in structures subjected to horizontal and vertical ground motions. Soil Dynamics and Earthquake Engineering, 2016. 81:p. 75-83.
8. 8. Castaldo, P. and M. Ripani, Optimal design of friction pendulum system properties for isolated structures considering different soil conditions. Soil Dynamics and Earthquake Engineering, 2016. 90:p. 74-87.

9. 9. Castaldo, P., B. Palazzo, and P.D., Vecchia, Seismic reliability of base-isolated structures with friction pendulum bearings. Engineering Structures, 2015. 95: p. 80-93.
10. 10. FEMA, NEHRP commentary on the guidelines for the seismic rehabilitation of buildings, 1997, Federal Emergency Management Agency, Report No. 274. Washington, DC.
11. 11. Jangid, R.S., Optimum friction pendulum system for near-fault motions. Engineering Structures, 2005. 27: p. 349-359.
12. 12. M. Ferraioli, M., A. Lavino, and A. Mandara, Behaviour Factor of Code-Designed Steel Moment-Resisting Frames. International Journal of Steel Structures, 2014. 14 (2): p. 243-254.
13. 13. Italian Code NTC08, Norme tecniche per le costruzioni in zone sismiche, 2008. Ministerial Decree D.M. 14.01.08, G.U. No.9-04.02.08 (in Italian).
14. 14. Tsai, C.S., T.C. Chiang, and B.J. Chen, Finite element formulations and theoretical study for variable curvature friction pendulum systems. Engineering Structures, 2003. 25. p:1719-30.
15. 15. Mazza, F. and M, Mazza, Nonlinear seismic analysis of irregular r.c. framed buildings base isolated with friction pendulum system under near-fault excitations. Soil Dynamics and Earthquake Engineering, 2016. 90: p. 299-312.
16. 16. Computers and Structures, Inc., SAP 2000 Advanced 14.0.0. Structural Analysis Program, 2011, Berkeley, CA.
17. 17. Park, Y.J., Y.K., Wen, and A.H., Ang, Random Vibration of Hysteretic Systems under bi-directional ground motions, Earthquake Engineering and Structural Dynamics, 1986. 14, p. 543-557.
18. 18. PEER, The Pacific Earthquake Engineering Research Center”. User’s Manual for the PEER Ground Motion Database Application, 2011, University of California, Berkeley.