بررسی اثر برخورد بر عملکرد قاب‌های فولادی جداسازی شده لرزه‌ای در جنبش‌های حوزه نزدیک

قلعه نوی, مونا; مسعودی, مصطفی

doi:10.22065/jsce.2019.190572.1887

بررسی اثر برخورد بر عملکرد قاب‌های فولادی جداسازی شده لرزه‌ای در جنبش‌های حوزه نزدیک

نوع مقاله : علمی - پژوهشی

نویسندگان

¹ کارشناس ارشد، دانشکدة مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی، تهران، ایران

² استادیار، دانشکدة مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی، تهران، ایران

10.22065/jsce.2019.190572.1887

چکیده

در سازه‌های جداسازی شده لرزه‌ای اگرچه ضوابط محافظه‌کارانه‌ای برای درز لرزه‌ای در نظر گرفته شده است و برخورد سازه‌های جداسازی شده لرزه‌ای با مانع یا دیوار بازدارنده عموماً پدیده‌ای نامطلوب تلّقی می‌شود ولی تمام جنبه‌های رفتار این سازه‌ها هنگام برخورد به طور کافی بررسی نشده است و نیاز به پژوهش‌های بیشتری دارد. آثار ناشی از برخورد این سازه‌ها وابسته به مقاومت و سختی جانبی، میرایی، درز لرزه‌ای موجود و همچنین مشخصات جنبش زمین است. هدف این پژوهش بررسی عملکرد ناکشسان قاب‌های خمشی فولادی جداسازی شده‌ با در نظر داشتن امکان برخورد در جنبش‌های پالسی حوزه‌ی نزدیک و مقادیر مختلف درز لرزه‌ای می‌باشد. برای این منظور دو قاب خمشی ویژه فولادی دارای جداگر الاستومری به صورت غیرخطی مدلسازی شد و جابجایی جداگر، شکل‌پذیری نیاز کلی و طبقه‌ای، ضریب کاهش مقاومت تسلیم و رانش میان طبقه‌ای تحت شتابنگاشت‌های مختلف بررسی گردید. نتایج نشان می‌دهد که پاسخ دینامیکی سازه‌ی جداسازی شده تحت برخورد در سطوح خطر لرزه‌ای بالا وابستگی زیادی به درز لرزه‌ای موجود، ارتفاع سازه (دوره تناوب) و الگوی بارگذاری دارد. با افزایش ارتفاع سازه پاسخ‌ها بویژه برای مقادیر بزرگ‌تر درز لرزه‌ای اختلاف کم‌تری با سازه‌ بدون برخورد خواهد داشت. همچنین پاسخ‌های روسازه برای همه مقادیر درز لرزه‌ای در حدود معیارهای قابل پذیرش برای سازه‌های پایه گیردار است.

کلیدواژه‌ها

موضوعات

کنترل فعال و غیر فعال سازه ها

عنوان مقاله [English]

Performance of base-isolated moment resisting steel frames subjected to pounding effects under near-field earthquake ground motions

نویسندگان [English]

Mona Ghalehnoy ¹
Mostafa Masoudi ²

¹ Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

² Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

چکیده [English]

Despite conservative requirements of existing building code regarding clear seismic gap distance of base-isolated (BI) structures to surrounding moat walls, seismic performance of these structures is still ambiguous under severe earthquake ground motions that may push the base slab of the isolation system to collide to the surrounding moat walls. Moreover, the temptation of reducing seismic gaps in congested urban areas exacerbates the risk of pounding. Excessive horizontal displacement response of these long-period structures subjected to a rare near-field ground motion may lead to pounding to adjacent structures and subsequently, severe and uncontrolled damage or even total collapse of the superstructure.
Pounding of BI structures to moat walls is usually considered as an unwanted response that may inflict critical damage to a high importance structure designed for high performance levels. Pounding effects to the moat walls depend on several parameters including superstructure and isolated periods, damping, seismic gap as well as characteristics of the earthquake ground motion. This study aims to evaluate seismic response of base-isolated moment resisting steel frames subjected to pounding effects under near-field earthquake ground motions with different clear gap distances to surrounding moat walls. A seven story and a three story buildings isolated with elastomeric bearings have been modeled. Base slab displacement, global displacement ductility demands, yield strength reduction factors, and maximum inter-story drifts have been computed under recorded severe near-field earthquake ground motions. Results showed that for most of the seismic gaps lower than those of prescribed by codes, seismic demands remain in acceptable ranges corresponding to low performance levels, i.e., life safety or collapse prevention of fixed-base structures. This implies that performance of BI buildings with codified seismic gaps or insufficient seismic gaps is not much different than that of fixed-base buildings when they are pushed to their displacement limits under maximum considered earthquakes.

کلیدواژه‌ها [English]

Seismic isolation
Pounding
Near-field ground motion
Steel moment resisting frame
Seismic gap
Seismic performance

مراجع

[1] Kelly, J. M. (1990). Base isolation: linear theory and design. Earthquake Spectra, 6(2), 223–244.

[2] Skinner, R. I. Robinson, W. H. and McVerry, G. H. (1993). An Introduction to Seismic Isolation. England. John Wiley & Sons

[3] Clemente, P. Martelli, A. (2018). Seismically isolated buildings in Italy: State-of-the-art review and applications. Soil Dynamics and Earthquake Engineering.

[4] Pan, P. Zamfirescu, D. Nakashima, M. Nakayasu, N. and Kashiwa, H. (2008). Base-isolation design practice in Japan: Introduction to the post-Kobe approach. Journal of Earthquake Engineering, 9. 147–171.

[5] Bessason, B. Hafliðason, E. and Guðmundsson, G. V. (2019). Performance of base isolated bridges in recent south Iceland earthquakes. In: Proceedings of the International Conference on Earthquake Engineering and Structural Dynamics. Cham, 47.

[6] Nagarajaiah, S. Sun, X. (2001). Base-isolated FCC building: impact response in Northridge earthquake. Journal of Structural Engineering, 127(9), 1063–1075.

[7] Jangid, R. S. Kelly, J. M. (2001). Base isolation for near-fault motions. Earthquake Engineering & Structural Dynamics, 30(5), 691–707.

[8] Tajammolian, H. Khoshnoudian, F. Talaei, S. and Loghman, V. (2014). The effects of peak ground velocity of near-field ground motions on the seismic responses of base-isolated structures mounted on friction bearings. Earthquakes and Structures, 7(6), 1259–1281.

[9] Alhan, C. Öncü-Davas, S. (2016). Performance limits of seismically isolated buildings under near-field earthquakes. Engineering Structures, 116, 83–94.

[10] Hall, J. F. Heaton, T. H. Halling, M. W. and Wald, D. J. (1995). Near‐source ground motion and its effects on flexible buildings. Earthquake Spectra, 11(4), 569–605.

[11] Tsai, H.-C. (1997). Dynamic analysis of base-isolated shear beams bumping against stops. Earthquake Engineering & Structural Dynamics, 26(5), 515–528.

[12] Malhotra, P. K. (1997). Dynamics of seismic impacts in base-isolated buildings. Earthquake Engineering & Structural Dynamics, 26(8), 797–813.

[13] Masroor, A. Mosqueda, G. (2015). Assessing the collapse probability of base-isolated buildings considering pounding to moat walls using the FEMA P695 methodology. Earthquake Spectra, 31(4), 2069–2086.

[14] Qu, Z. Kishiki, S. and Nakazawa, T. (2013). Influence of isolation gap size on the collapse performance of seismically base-isolated buildings. Earthquake Spectra, 29(4), 1477–1494.

[15] Ye, K. Li, L. and Zhu, H. (2009). A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures. Earthquake Engineering and Engineering Vibration, 8(3), 433–446.

[16] Komodromos, P. Polycarpou, P. C. Papaloizou, L. and Phocas, M. C. (2007). Response of seismically isolated buildings considering poundings. Earthquake Engineering & Structural Dynamics, 36(12), 1605–1622.

[17] Bao, Y. Becker, T. C. and Hamaguchi, H. (2017). Failure of double friction pendulum bearings under pulse-type motions. Earthquake Engineering & Structural Dynamics, 46(5), 715–732.

[18] Masoudi, M. Ghalehnoy, M. (2020). Seismic response of base-isolated structures with insufficient gaps. Sharif Journal of Civil Engineering, doi: 10.24200/J30.2018.5558.2387 (in persian).

[19] Filiatrault, A. Wagner, P. and Cherry, S. (1995). Analytical prediction of experimental building pounding. Earthquake Engineering & Structural Dynamics, 24(8),1131–1154.

[20] Lankarani, H. M. (1994). Continuous contact force models for impact analysis in multibody systems. Nonlinear Dynamics, 5, 193–207.

[21] American Society of Civil Engineers, (2017). Minimum Design Loads and Associated Criteria for Buildings and Other Structures-ASCE/SEI 7-16. Reston. VA: American Society of Civil Engineers.

[22] American Society of Civil Engineers, (2014). Seismic Evaluation and Retrofit of Existing Buildings-ASCE/SEI 41-17. Reston. VA: American Society of Civil Engineers.

[23] Naeim, F. and Kelly, J.M. (1999). Design of Seismic Isolated Structures: from Theory to Practice. New York: John Wiley.

[24] Matsagar, V. A. Jangid, R. S. (2003). Seismic response of base-isolated structures during impact with adjacent structures. Engineering Structures, 25(10), 1311–1323.

[25] Komodromos, P. (2008). Simulation of the earthquake-induced pounding of seismically isolated buildings. Computers & Structures, 86(7–8), 618–626.

[26] Iranian Building Codes and Standards, (2014-1393). Iranian Code of Practice for Seismic Resistant Design of buildings, Standard No.2800, 4^thEdition.