PREDICTION MODEL FOR BASE SHEAR INCREASE DUE TO VERTICAL GROUND MOTION IN FRICTION PENDULUM ISOLATED STRUCTURES

Abstract

Seismic isolation is one of the most effective seismic hazard mitigation techniques, which has been implemented in many structures. Friction pendulum isolators are one of the most popular isolation devices to achieve energy dissipation and shear resistance that depends on the effective radius and instantaneous vertical force on them. So, the horizontal response of this type of isolators is coupled with the axial load on them, which could change due to vertical acceleration during ground shaking. Thus, it makes consideration of the vertical excitation in the design and analysis phase inevitable, especially for structures in those regions where vertical ground accelerations are more pronounced. In this study a model for the prediction of increase in base shear due to vertical motion for friction pendulum isolated structures is proposed. A simple single friction pendulum isolator system is utilized with the assumption of rigid superstructure on top and subjected to a hundred earthquake ground motions with different characteristics. A multi-layer perceptron model with three layers is utilized, and a simple computer program, which is open-source, is prepared to construct probability curves. With the help of the program, within the range of the considered structural parameters in the study, probability curves related to increase in base shear, maximum isolator displacement and residual isolator displacement can be constructed, and designers can have a rough estimation on modification of these parameters due to vertical ground motion.

Keywords

• Seismic isolation
• Friction pendulum system
• Vertical Ground Motion
• Base Shear Increase

Düşey yer hareketinden dolayı sürtünmeli sarkaç sistemleri ile izole edilmiş yapılarda taban kesme kuvveti artışı tahmin modeli

Abstract

Birçok yapıya uygulanan sismik izolasyon, sismik tehlikenin azaltılması için en etkin yollardan biridir. Sürtünmeli sarkaç izolatörleri de enerji sönümü ve etkili yarı çapa ve üzerindeki anlık yüke bağlı olarak kayma direnci oluşturan en popüler sismik izolatörlerdendir. Bu yüzden, bu tür izolatörlerin yatay tepkisi üzerinde bulunan eksenel yüke bağlıdır ve bu yük de düşey yer ivmesine göre sarsıntı boyunca değişebilir. Böylece düşey yer sarsıntısının etkili olduğu bölgelerde bu doğrultudaki ivmeyi tasarım ve analiz aşamasında göz önünde bulundurmayı kaçınılmaz kılar. Bu nedenle, bu çalışmada taban kesme kuvvetinde düşey hareketten dolayı meydana gelen artımın tahmini için bir yöntem sunulmaktadır. Rijit yapı kabulüne dayalı basit bir model oluşturulmuş ve farklı karakterlere sahip yüz deprem hareketine maruz bırakılmıştır. Çok katmanlı algılayıcı modeli kullanılmış ve kırılganlık eğrilerinin oluşturulması için açık kaynak kodlu basit bir bilgisayar programı hazırlanmıştır. Program yardımıyla çalışmada verilen yapısal parametrelerin aralığında taban kesme kuvvetinde, maksimum ve kalıcı izolatör deplasmanında düşey yer ivmesinden dolayı meydana gelecek artışa dair olasılık eğrileri elde edilebilir ve tasarımcılar düşey yer ivmesinden dolayı bu parametrelerde yapılacak olan modifikasyonlar için yaklaşık bir tahmin yapabilir.

Keywords

• Sismik izolasyon
• Sürtünmeli Sarkaç Sistemi
• Düşey Yer Hareketi
• Taban kesme kuvveti artışı

References

1. 1. Abadi, M., Agarwal, A., Barham, P., Brevdo, E., Chen, Z., Citro, C., Corrado, G. S., Davis, A., Dean, J., Devin, M., Ghemawat, S., Goodfellow, I., Harp, A., Irving, G., Isard, M., Jozefowicz, R., Jia, Y., Kaiser, L., Kudlur, M., Levenberg, J., Mané, D., Schuster, M., Monga, R., Moore, S., Murray, D., Olah, C., Shlens, J., Steiner, B., Sutskever, I., Talwar, K., Tucker, P., Vanhoucke, V., Vasudevan, V., Viégas, F., Vinyals, O., Warden, P., Wattenberg, M., Wicke, M., Yu, Y., and Zheng. X. (2015) TensorFlow: Large-scale machine learning on heterogeneous systems, Software available from tensorflow.org.
2. 2. Baker J. W. (2021) Baker Reseacrh Group, Stanford University, https://web.stanford.edu/~bakerjw/gm_selection_old.html
3. 3. Baker, J. W. and Jayaram, N. (2008) Correlation of spectral acceleration values from NGA ground motion models, Earthquake Spectra, 24(1), 299-317. doi: 10.1193/1.2857544
4. 4. Baker, J. W., Lin, T., Shahi, S. K. and Jayaram, N. (2011) New ground motion selection procedures and selected motions for the PEER Transportation Research Program, PEER Technical Report 2011/03.
5. 5. Cilsalar, H. and Constantinou, M. C. (2017) Effect of vertical ground motion on the response of structures isolated with friction pendulum isolators, International Journal of Earthquake and Impact Engineering, 2(2), 135-157. doi:10.1504/IJEIE.2017.089048
6. 6. Constantinou, M., Mokha, A. and Reinhorn, A. (1990) Teflon bearings in base isolation II: Modeling, Journal of Structural Engineering, 116(2), 455-474. doi: 10.1061/(ASCE)0733-9445(1990)116:2(455)
7. 7. Dao, N. D. and Ryan, K. L. (2020) Soil–structure ınteraction and vertical-horizontal coupling effects in buildings ısolated by friction bearings, Journal of Earthquake Engineering, 1-24. doi: 10.1080/13632469.2020.1754969
8. 8. Dao, N. D., Ryan, K. L. and Nguyen‐Van, H. (2019) Evaluating simplified models in predicting global seismic responses of a shake table–test building isolated by triple friction pendulum bearings, Earthquake Engineering & Structural Dynamics, 48(6), 594-610. doi: 10.1002/eqe.3152

9. 9. Eltahawy, W., Ryan, K. L., Cesmeci, S. and Gordaninejad, F. (2018) Parameters affecting dynamics of three-dimensional seismic isolation, Journal of Earthquake Engineering, 1-26. doi: 10.1080/13632469.2018.1537902
10. 10. FEMA (2009) Quantification of building seismic performance factors, Technical Report FEMA P695, Federal Emergency Management Agency, Washington, D.C.
11. 11. Fenz, D.M. and Constantinou, M. C. (2006) Behavior of the double concave friction pendulum bearing, Earthquake Engineering & Structural Dynamics, Vol. 35, No. 11, pp.1403–1424. doi: 10.1002/eqe.589
12. 12. Fenz, D.M. and Constantinou, M. C. (2008) Modeling triple friction pendulum bearings for response history analysis, Earthquake Spectra, Vol. 24, No. 2, pp.1011–1028. doi: 10.1193/1.2982531
13. 13. Guzman Pujols, J. C. and Ryan, K. L. (2017) Computational simulation of slab vibration and horizontal‐vertical coupling in a full‐scale test bed subjected to 3D shaking at E‐Defense, Earthquake Engineering & Structural Dynamics, 47(2), 438-459. doi: 10.1002/eqe.2973
14. 14. Jayaram, N. and Baker, J. W. (2010) Ground-Motion Selection for PEER Transportation Research Program, Proceedings, 7th International Conference on Urban Earthquake Engineering (7CUEE) & 5th International Conference on Earthquake Engineering (5ICEE), Tokyo, Japan, 9p.
15. 15. Jayaram, N., Lin, T. and Baker, J. W. (2011) A computationally efficient ground-motion selection algorithm for matching a target response spectrum mean and variance, Earthquake Spectra, 27(3), 797-815. doi: 10.1193/1.3608002
16. 16. Kitayama, S. and Constantinou, M. C. (2018) Collapse performance of seismically isolated buildings designed by the procedures of ASCE/SEI 7, Engineering Structures, 164, 243-258. doi: 10.1016/j.engstruct.2018.03.008
17. 17. Kumar, M., Whittaker, A.S. and Constantinou, M. C. (2015a) Characterizing friction in sliding isolation bearings, Earthquake Engineering & Structural Dynamics, Vol. 44, No. 9, pp.1409–1425. doi: 10.1002/eqe.2524
18. 18. Kumar, M., Whittaker, A. S. and Constantinou, M. C. (2015b) Seismic isolation of nuclear power plants using sliding bearings, Technical Report MCEER-15-0006, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY.
19. 19. McKenna, F. T. (1997) Object-oriented finite element programming: frameworks for analysis, algorithms and parallel computing, Ph.D. Thesis, University of California, Berkeley.
20. 20. McVitty, W. J. and Constantinou, M. C. (2015) Property modification factors for seismic isolators: Design Guidance for Buildings. Technical Report MCEER-15-0005, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY.
21. 21. Mokha, A., Constantinou, M.C., Reinhorn, A.M. and Zayas, V.A. (1991) Experimental study of friction-pendulum isolation system, Journal of Structural Engineering, Vol. 117, No. 4, pp.1201–1217. doi: 10.1061/(ASCE)0733-9445(1991)117:4(1201)
22. 22. Morgan, T.A. (2007) The use of ınnovative base ısolation systems to achieve complex seismic performance objectives, PhD thesis, University of California, Berkeley, CA, USA.
23. 23. Oikonomou, K., Constantinou, M., Reinhorn, A. and L. Kempner, J. (2016) Seismic ısolation of high voltage electric power transformers, Technical Report MCEER-16-0006, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY.
24. 24. Panchal, V. R., Jangid, R. S., Soni, D. P. adn Mistry, B. B. (2010). Response of the double variable frequency pendulum isolator under triaxial ground excitations, Journal of Earthquake Engineering, 14(4), 527-558. doi: 10.1080/13632460903294390
25. 25. PEER 2021, Pacific Earthquake Engineering Research Center Ground Motion Database, https://ngawest2.berkeley.edu/
26. 26. Ryan, K. L. and Dao, N. D. (2016) Influence of vertical ground shaking on horizontal response of seismically isolated buildings with friction bearings, Journal of Structural Engineering, 142(1), 04015089. doi: 10.1061/(ASCE)ST.1943-541X.0001352
27. 27. Sarlis, A., Constantinou, M.C. and Reinhorn, A. (2013) Shake table testing of triple friction pendulum ısolators under extreme conditions, Technical Report MCEER-13-0001, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY.
28. 28. Shakib, H. and Fuladgar, A. (2003) Effect of vertical component of earthquake on the response of pure-friction base-isolated asymmetric buildings, Engineering structures, 25(14), 1841-1850. doi: 10.1016/j.engstruct.2003.08.008
29. 29. Zayas, V.A., Low, S.S. and Mahin, S.A. (1987) The FPS Earthquake Resisting System: Experimental Report, Report No. UCB/EERC/-87/01, Earthquake Engineering Research Center, University of California Berkeley, CA, USA.
30. 30. Zhu, M., McKenna, F. and Scott, M. H. (2018) OpenSeesPy: Python library for the OpenSees finite element framework, SoftwareX, 7, 6-11. doi: 10.1016/j.softx.2017.10.009