Investigation of the Effects of Superstructure Damping Ratio on Buildings with Lead Rubber Bearings under Earthquake Effect

Yıl 2022, Cilt: 25 Sayı: 2, 655 - 665, 01.06.2022

Zafer Kanbir , Cenk Alhan , Gökhan Özdemir

https://doi.org/10.2339/politeknik.803212

Cited By: 1

Öz

Lead rubber bearings (LRBs) are among the most commonly used seismic isolation bearing types due to their high energy dissipation capacity. However, the experimental studies reveal that the temperature rise occurring under cyclic loads in the lead core, causes a deterioration in the characteristic strength by decreasing the yield strength of the lead, and it is important to consider this effect. In seismically isolated buildings, in addition to the isolation system, the superstructure also has a degree of energy dissipation capacity thanks to its inherent damping. It is seen that different damping ratios are used in the designs of such structures and research studies dealing with these structures. In this study, the change in the temperature-dependent behavior of seismically isolated buildings is investigated in cases where (i) superstructure damping is taken as 5% similar to fixed base reinforced concrete buildings, (ii) superstructure damping is taken as a smaller value such as 2%, and (iii) superstructure damping is completely neglected. A seismically isolated reinforced concrete building is modeled in the OpenSees program, considering the effect of the lead core heating on the characteristic strength and responses such as floor accelerations, temperature increase in the lead core, bearing shear forces and displacements obtained from nonlinear time history analyses are investigated. The results obtained showed that especially the floor accelerations can vary significantly and the floor accelerations obtained with different superstructure damping ratios can be in different limit ranges.

Anahtar Kelimeler

lead rubber bearings, lead core heating, seismic base isolation, superstructure damping

Üstyapı Sönüm Oranının Deprem Etkisindeki Kurşun Çekirdekli Elastomer Yalıtım Birimli Binalardaki Etkilerinin Araştırılması

Öz

Kurşun çekirdekli elastomer (KÇE) yalıtım birimleri yüksek enerji sönümleme kapasiteleri nedeniyle en çok kullanılan sismik yalıtım birimleri arasında yer almaktadır. Bununla birlikte, yapılan deneysel çalışmalar; kurşun çekirdekte tersinir yükler altında meydana gelen sıcaklık artışının, kurşunun akma dayanımını düşürerek karakteristik dayanımda azalmaya yol açtığını ve bu etkiyi dikkate almanın önemli olduğunu ortaya koymaktadır. Sismik yalıtımlı binalarda yalıtım sisteminin yanı sıra, üstyapı da kendi iç sönümü sayesinde bir dereceye kadar enerji sönümleme özelliğine sahiptir. Ancak, bu yapıların tasarımlarında ve bu tür yapıları ele alan araştırma çalışmalarında üstyapı için farklı sönüm oranlarının kullanıldığı görülmektedir. Bu çalışmada, üstyapı sönümünün, (i) taban ankastre betonarme binalara benzer şekilde % 5 alınması, (ii) % 2 gibi daha küçük bir değer alınması ya da (iii) tamamen ihmal edilmesi durumunda sismik yalıtımlı binaların kurşun çekirdek ısınmasına bağlı davranışlarının değişimi incelenmiştir. Sismik yalıtımlı betonarme bir bina, OpenSees programında, kurşun çekirdek ısınmasının dayanım üzerindeki etkisi göz önünde bulundurularak modellenmiş ve zaman tanım alanında yapılan doğrusal olmayan analizlerden elde edilen kat ivmeleri, kurşun çekirdekteki sıcaklık artışı, yalıtım birimi kesme kuvvetleri ve deplasmanları gibi tepkiler incelenmiştir. Sonuçlar, özellikle kat ivmelerinin önemli ölçüde değişebildiğini ve farklı üstyapı sönüm oranlarıyla elde edilen kat ivmelerinin farklı sınır aralıklarında olabileceğini ortaya koymuştur.

Anahtar Kelimeler

kurşun çekirdekli elastomer yalıtım birimleri, kurşun çekirdek ısınması, sismik taban yalıtımı, üst yapı sönümü

Kaynakça

• [1] Worksafe Technologies, “ISO-Base Seismic Isolation Platform Brochure” http://www.powerprotection. co.nz/wp-content/uploads/2018/03/IsoBase-Brochure. pdf [Ziyaret Tarihi: 20.09.2020].
• [2] Mizuno H., Iiba M., Yamaguchi N. and Okano H., “Shaking table testing on earthquake resistance of medical equipments”, Report of the Building Research Institute, Building Research Institute, Ministry of Construction, (1986).
• [3] T.C. Sağlık Bakanlığı, “Deprem Yalıtımlı Olarak İnşa Edilecek Yapılara Ait Proje ve Yapım İşlerinde Uyulması Gereken Asgari Standartlar” Genelge 2013/3, (2013).
• [4] Naeim F. and Kelly J. M., “Design of Seismic Isolated Structures: From Theory to Practice”, JohnWiley & Sons, New York, (1999).
• [5] Skinner R. I., Robinson W. H. and McVerry G. H., “An Introduction to Seismic Isolation”, Wiley, Chichester, UK, (1993).
• [6] Robinson W. H., “Lead-rubber hysteretic bearings suitable for protecting structures during earthquakes”, Earthquake Engng Struct. Dyn., 10(4):593-604 (1982).
• [7] Constantinou M. C., Whittaker A. S., Kalpakidis Y., Fenz D. M., and Warn G. P., “Performance of seismic isolation hardware under service and seismic loading”, Technical Rep. No. MCEER-07-0012; Multidisciplinary Center for Earthquake Engineering Research, Buffalo, N.Y., (2007).
• [8] Kalpakidis I. V., and Constantinou M. C., “Effects of heating and load history on the behavior of lead-rubber bearings”, Technical Rep. No. MCEER-08-0027; Multidisciplinary Center for Earthquake Engineering Research, Buffalo, N.Y., (2008).
• [9] Kalpakidis I. V. and Constantinou M. C., “Effects of heating on the behavior of lead-rubber bearing. I:theory”, J Struct Eng., 135(12):1440-1449, (2009).
• [10] Özdemir G., “Lead core heating in lead rubber bearings subjected to bidirectional ground motion excitations in various soil types”, Earthquake Engineering and Structural Dynamics, 43(2):267-285, (2014).
• [11] Özdemir G., Bayhan B., and Gülkan P., “Variations in the hysteretic behavior of LRBs as a function of applied loading”, Structural Engineering and Mechanics, 67(1):69-78, (2018).
• [12] Kanbir Z., Alhan C., and Özdemir G., “Influence of Superstructure Modeling Approach on the Response Prediction of Buildings with LRBs Considering Heating Effects” Structures, 28:1756-1773, (2020).
• [13] Chopra A. K., “Dynamics of Structures”, Fourth Ed., Prentice Hall, Boston, MA, (2012).
• [14] Fan F. G. and Ahmadi G., “Seismic response of secondary system in base isolated structures”, Engineering Structures, 14:35-48, (1992).
• [15] Matsagar V. A. and Jangid RS., “Influence of isolator characteristics on the response of base-isolated structures”, Engineering Structures, 26:1735-1749, (2004).
• [16] Providakis C. P., "Effect of LRB isolators and supplemental viscous dampers on seismic isolated buildings under near-fault excitations", Engineering structures, 30(5):1187-1198, (2008).
• [17] Kilar V. and Koren D., “Seismic Behavior of Asymmetric Base Isolated Structures with Various Distributions of Isolators”, Engineering Structures, 31:910-921, (2009).
• [18] Kanbir Z., “Kurşun Çekirdekteki Isınmanın Sismik İzolasyonlu Yapıların Davranışına Etkisi”, Yayınlanmamış Doktora Tezi, İstanbul Üniversitesi - Cerrahpaşa, Lisansüstü Eğitim Enstitüsü, İstanbul, (2020).
• [19] McKenna F., Fenves G. and Scott M., “OpenSees: Open System for Earthquake Engineering Simulation”, Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, USA, (2006). http://opensees.berkeley.edu
• [20] Schellenberg A., Yang T. and Kohama E., “OpenSees Navigator: MATLAB based graphical user interface”, Pacific Earthquake Engineering Research Center, Berkeley, CA, (2016). http://openseesnavigator. berkeley.edu
• [21] Hall J. F., “Problems encountered from the use (or misuse) of Rayleigh damping”, Earthquake Engineering and Structural Dynamics, 35(5):525-545, (2006).
• [22] Alhan C. and Şahin F., “Protecting vibration-sensitive contents: an investigation of floor accelerations in seismically isolated buildings”. Bull Earthquake Eng, 9:1203–26, (2011).
• [23] Alhan C. and Sürmeli M., “Shear building representations of seismically isolated buildings”, Bull Earthquake Eng, 9(5):1643-1671, (2011).
• [24] Shao B. and Mahin S.A., “A probabilistic design method to achieve targeted levels of reliability for seismically isolated structure”, Earthquake Spectra, 36(2):741-766, (2020).
• [25] Güneş N. ve Ulucan Z. Ç., “Farklı tasarlanmış iki sismik yalıtımlı binanın karşılaştırılması”, Fırat Üniversitesi Müh Böl Dergisi, 32:37–46, (2020).
• [26] Constantinou M. C., Whittaker A. S., Fenz D. M., and Apostolakis G., “Seismic Isolation of Bridges”, New York, Report Submitted to the State of California Department of Transportation, University at Buffalo, Version 2, (2007).
• [27] AASHTO, American Association of State Highway and Transportation Officials “Guide Specification for Seismic Isolation Design” Washington, DC, (2010).
• [28] ASCE, American Society of Civil Engineers “Minimum design loads and associated criteria for buildings and other structures” Standard ASCE/SEI 7-16, Reston, VA., (2017).
• [29] Caltrans, California Department of Transportation, “Caltrans Seismic Design Criteria”, Version 1.3., (2004).
• [30] FEMA 440, Applied Technology Council “Improvement of Nonlinear Static Seismic Analysis Procedures” Report Federal Emergency Management Agency, Washington, D.C., (2005).
• [31] Kanbir Z., Özdemir G. and Alhan C., “Modeling of Lead Rubber Bearings via 3D-BASIS, SAP2000, and OpenSees Considering Lead Core Heating Modeling Capabilities”, International Journal of Structural and Civil Engineering Research, 7(4):294-301, (2018).
• [32] Heaton T. H., Hall J. F., Wald D. J., and Halling M. W., “Response of high-rise and base-isolated buildings to a hypothetical Mw 7.0 blind thrust earthquake” Science, 267: 206-211, (1995).
• [33] Kalpakidis I. V., Constantinou M. C., and Whittaker A. S., “Modeling strength degradation in lead-rubber bearings under earthquake shaking” Earthquake Engineering and Structural Dynamics, 39(13):1533-1549, (2010).
• [34] Özdemir G. and Dicleli M., “Effect of lead core heating on the seismic performance of bridges isolated with LRB in near-fault zones” Earthquake Engineering and Structural Dynamics, 41(14):1989–2007, (2012).
• [35] PEER Pacific Earthquake Engineering Research Center Ground Motion Database; University of California, Berkeley, CA, (2013). http://ngawest2.berkeley.edu
• [36] Baker J. W., “Conditional mean spectrum: Tool for ground-motion selection”, Journal of Structural Engineering, 137(3): 322–331, (2011).