ارزیابی منحنی شکنندگی سازه‌های نامنظم بتن آرمه در زلزله‌های نزدیک گسل تحت پیچش با در نظر گرفتن اندرکنش خاک – سازه

نوع مقاله : مقاله پژوهشی

نویسنده

استادیار رشته مهندسی عمران، دانشگاه آزاد اسلامی، واحد اصفهان (خوراسگان)، اصفهان، ایران

چکیده

در سازه‌های واقعی علاوه بر پیچش در پلان، پدیده اندرکنش خاک و سازه نیز رخ می‌دهد که این دو پدیده در تحلیل‌ها به ندرت به صورت همزمان در نظر گرفته شده‌اند. در تحقیق حاضر، با استفاده از منحنی‌های شکنندگی، احتمال از بین رفتن قابلیت خدمت‌رسانی بی‌وقفه و ایمنی جانی در سازه نامتقارن در پلان با در نظر گرفتن اندرکنش خاک و سازه، تحت تحریک‌های نزدیک به گسل (دارای پالس) مورد ارزیابی قرار گرفته است. سازه مورد بررسی یک سازه هشت طبقه بتنی با سیستم باربر دوگانه قاب خمشی و دیوار برشی است. یکی از نوآوری‌های این تحقیق، استفاده از شاخص کرنش فولاد و بتن (به جای استفاده از شاخص‌های رایج ماکرو، نظیر دریفت طبقات) برای تعیین حالت‌های حدی است که از دقت بیشتری برخوردار است. برای در نظر گرفتن اثرات پدیده اندرکنش، از روش زیر سازه استفاده شده است که مقادیر سختی و میرایی (توابع امپدانس) با استفاده از روش نیمه تحلیلی Novak (نرم‌افزار DYNA5) محاسبه شده است. مدل‌‌سازی غیرخطی سازه برای دست‌یابی به حل تاریخچه زمانی غیرخطی، با استفاده از نرم‌افزار Canny انجام شده است. برای استخراج منحنی‌های شکنندگی، از تحلیل‌های دینامیکی افزاینده استفاده شده است. نتایج این تحقیق نشان می‌دهد که صرف‌نظر از پدیده اندرکنش خاک و سازه، در سطوح عملکرد خدمت‌رسانی بی‌وقفه و ایمنی جانی، در جهت اطمینان نیست. همچنین با افزایش خروج از مرکزیت، تأثیرات شرایط تکیه­گاهی کاهش می‌یابد و از سوی دیگر با کاهش سرعت موج برشی خاک، تأثیرات خروج از مرکزیت کاهش می‌یابد و پاسخ سازه نامتقارن و متقارن به یکدیگر نزدیک می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evaluation of Fragility Curves of Asymmetric-Plan Reinforced Concrete Structures in the Near-Fault Earthquakes under the Effect of Torsion Considering Soil-Structure Interaction

نویسنده [English]

  • Mohammad sadegh Birzhandi
Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran
چکیده [English]

In this study, the life safety and immediate occupancy of asymmetric-plan reinforced concrete dual structures under the simultaneous effect of torsion and soil-structure interaction in the near-fault pulse-like earthquakes were evaluated using a probabilistic framework. An 8-story R/C dual lateral load resistant building consisting of shear walls and moment-resisting frames was used. The sub-structure method was used to simulate the SSI effect. The impedance functions were calculated with the Novak semi-analytical method (DYNA5 software). The structure was modeled in the CANNY software considering the nonlinear behavior to perform the nonlinear time history analysis. All of the ground motion records were selected from the near-fault pulse-like records. Incremental dynamic analysis was employed to extract and fragility curves. To determine the life safety and immediate occupancy limit states, the strain of steel and concrete (as a micro index) were used rather than the usual macro indexes such as story drifts that lead to increase the accuracy of results. One of the most important of the conclusion is that neglecting the SSI effect in the life safety and immediate occupancy limit states for the plan-asymmetric structure is not in the safe side and lead to overestimation in the structural capacity. Also, an increase in the mass eccentricity leads to a decrease in the base conditions' importance and SSI effect. Another considerable observation is that an increase in the shear wave velocity of soil can lead to a decrease in the torsional response and the seismic response of asymmetric structure approaches to the symmetric one.

کلیدواژه‌ها [English]

  • Plan-asymmetric structures
  • soil-structure interaction (SSI)
  • Life safety
  • Immediate Occupancy
  • Near-fault pulse-like earthquakes
  1. Halabian, M. S. Birzhandi, Inelastic response of bi-eccentric plan asymmetric RC buildings, Journal of Structures and buildings, 167 (SB8) (2014) 469-485.
  2. Crouse, Commentary on soil-structure interaction in U.S. seismic provisions, Proc. 7th U.S. National Conference on Earthquake Engineering: Boston (2002).
  3. Emami, Effect of Foundation-Flexibility on Ductility Demand of 3D R/C Frame Structures, Master's Thesis, Isfahan University of Technology (2008) (in Persian).
  4. Nakhaei, M. A. Ghannad, The effect of soil–structure interaction on damage index of buildings, Engineering Structures, 30 (2008) 1491–1499.
  5. E. Rodriguez, R. Montes, Seismic response and damage analysis of buildings supported on flexible soils, Earthquake Engineering and Structural Dynamics, 29 (2000) 647-665.
  6. H. Wu, J. F. Wang, C. C. Lin, Systematic assessment of irregular building-soil interaction using efficient modal analysis, Earthquake Engineering and Structural Dynamics, 30 (2001) 573-594.
  7. Fuladgar, Effect of Multicomponent Earthquakes on Asymmetric Buildings by Considering Sliding Supports and Flexible Foundation, Ph.D. Thesis, Tarbiat Modares University, (2001) (in Persian).
  8. Shakib, Evaluation of dynamic eccentricity by considering soil–structure interaction: a proposal for seismic design codes, Soil Dynamics and Earthquake Engineering, 24 (2004) 369–378.
  9. Saez, F. Lopez-Caballero, A. Modaressi-Farahmand-Razavi, Effect of the inelastic dynamic soil–structure interaction on the seismic vulnerability assessment, Structural Safety, 33 (2011) 51–63.
  10. Barcena, L. Esteva, Influence of dynamic soil–structure interaction on the nonlinear response and seismic reliability of multistorey systems, Earthquake Engineering and Structural Dynamics, 36 (2007) 327–346.
  11. Tang, J. Zhang, Probabilistic seismic demand analysis of a slender RC shear wall considering soil-structure interaction effects, Engineering Structures, 33(1) (2011) 218-229.
  12. S. Birzhandi, A. M. Halabian, Probabilistic assessment of plan-asymmetric structures under the near-fault pulse-like events considering soil–structure interaction, Advances in Structural Engineering, 22(3) (2019) 702–721.
  13. Homaei, H. Shakib, Probabilistic confidence level evaluation of vertically irregular steel buildings considering soil–structure interaction, Sharif Journal of Civil Engineering, 33.2(3.2), (2017) 17-27, (in Persian).
  14. P. Wolf, Dynamic Soil-Structure Interaction; Prentice-Hall: New Jersey, 1985.
  15. E. Richart, J. R. Hall, R. D. Woods, Vibrations of soils and foundations, Prentice-Hall, Englewood Cliffs, N.J, (1970).
  16. P. Wolf, Spring-dashpot-mass models for foundation vibrations, Earthquake Engineering and Structural Dynamics, 26 (1997) 931–949.
  17. Novak, M. Sheta, L. El-Hifnawy, H. El-Marsafawi, O. Ramadan, (1993) DYNA5: A Computer Program for Calculation of Foundation Response to Dynamic Loads. Geotechnical Research Center, University of Western Ontario.
  18. Li, CANNY, (2002), Technical Manual (Version CO2): 3-Dimensional Nonlinear Static/ Dynamic Computer Program.
  19. W. Baker, Quantitative classification of near-fault ground motions using wavelet analysis, Bulletin of the Seismological Society of America, 97(5) (2007) 1486–1501.
  20. Liel, The effect of near-fault directivity on building seismic collapse risk, Award Number: G10AP00041, Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, (2010).
  21. L. Kramer, Geotechnical Earthquake Engineering, Prentice-Hall, International Series in Civil Engineering and Engineering Mechanics, Upper Saddle River, New Jersey, 1996.
  22. FEMA, Quantification of Building Seismic Performance Factors: FEMA P695, Federal Emergency Management Agency, Washington, D.C., 2009.
  23. FEMA, Prestandard and Commentary for the Seismic Rehabilitation of Buildings: FEMA 356, Federal Emergency Management Agency, Washington, D.C., 2000.
  24. ASCE, Seismic Rehabilitation of Existing Buildings: ASCE/SEI 41-06, American Society of Civil Engineers, Reston, Virginia, 2009.
  25. Kircher, A. A. Nassar, O. Kustu, W. T. Holmes, Development of building damage functions for earthquake loss estimation. Earthquake Spectra 13(4) (1997) 663–682.
  26. ICBO (1997) Uniform Building Code, 1997 Edition. International Conference of Building Officials: Whittier, CA, 1997.
  27. J. N. Priestley, G. M. Calv, M. J. Kowalsky, Displacement-Based Seismic Design of Structures. Pavia: IUSS Press, 2007.