ارزیابی آسیب‌پذیری قاب‌های ضعیف بتن مسلح مقاوم شده با روش‌ها و ترازهای مختلف به کمک منحنی شکنندگی و تحلیل هزینه فایده

نوع مقاله : Articles

نویسندگان

دانشکده عمران، دانشگاه صنعتی اصفهان

چکیده

با کمک راهکارهای مختلف سازه‌ای مانند افزودن عناصر جدید لرزه‌بر و یا افزایش مقاومت و شکل‌پذیری عناصر موجود، ظرفیت سازه‌های ضعیف در برابر تحریک زلزله تا حد پذیرش آیین‌نامه بهسازی افزایش می‌یابد. اما با توجه به احتمالاتی بودن اثر تحریک زلزله، لازم است اثر این مقاوم‌سازی بر روی عملکرد احتمالاتی سازه سنجیده شود. در این مقاله، با توجه به تنوع راهکارهای مقاوم‌سازی و امکان انجام آن در ترازهای مختلف، چارچوبی با استفاده از منحنی‌های شکنندگی استفاده شده است، تا ضمن لحاظ اثرات احتمالاتی رخداد زلزله، به کمک تحلیل هزینه‌فایده بهترین و مناسب‌ترین راهکار مقاوم‌سازی انتخاب گردد. بدین‌منظور، دو روش اضافه کردن دیوار برشی بتن‌آرمه و استفاده از ورق‌های الیاف کربنی مسلح پلیمری (CFRP) برای مقاوم‌سازی سازه‌های ضعیف بتنی استفاده شده است. آسیب‌پذیری سازه‌های مقاوم شده در ترازهای مختلف مقاوم‌سازی،  نسبت به سازه ضعیف اولیه ارزیابی شده است. نتایج تحلیل‌ها برای سازه‌های 5، 8 و 15 طبقه مورد بررسی، نشان داده است که استفاده از ورق‌های CFRP همواره اقتصادی‌تر است، ولی چون دیوارهای برشی در شدت‌های بالای زلزله، احتمال فراگذشت از حدود عملکردی آستانه فروریزش را بیشتر کاهش می‌دهند، در سازه‌های بلند که آسیب‌پذیرتر هستند، نسبت ‌فایده به هزینه، دو روش به یکدیگر نزدیک شده‌اند.

کلیدواژه‌ها


عنوان مقاله [English]

Vulnerability Assessment of Retrofitted Weak Reinforced Concrete Frames with Different Methods and Levels Using Fragility Curves and Cost-Benefit Analysis

نویسندگان [English]

  • Payam Asadi
  • Hossein Baharlou
Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran
چکیده [English]

Purpose
Different structural solutions are employed to enhance the capacity of weak structures under the earthquake excitations to satisfy the target of the rehabilitation regulations. These retrofitting methods include adding new seismic-resistant components or increasing the strength and ductility of existing components. Given the probability of the earthquake occurrence, it is necessary to evaluate the effect of different retrofitting scenarios on the probabilistic performance of the structure. In this paper, a framework using fragility curves is presented to select the most efficient retrofit scenario in terms of the cost-benefit analysis. For this purpose, two methods of adding reinforced concrete (RC) shear walls and use of polymeric reinforced carbon fiber (CFRP) sheets are employed to retrofit weak RC frames of 5, 8 and 12-stories. Different retrofitting scenarios for RC frames were compared using the proposed framework.
Methodology
Following the presented framework, the damage indices of structures of each scenario are extracted from the incremental nonlinear dynamic analysis. Then, the fragility curve, the damage probability matrix, and the expected annual damage costs are obtained. In the last step, different scenarios were compared using cost-benefit analysis. The benefits and costs included in the cost-benefit analysis were the reductions of the annual damage cost and cost of each structural retrofitting scenario, respectively. The higher the benefit-cost ratio, the more economical the scenario is. IDARC [1] software was employed for dynamic nonlinear structural analysis. For modeling the hysteresis deteriorations in dynamic analyses, stiffness, resistance, and pinching deterioration parameters were employed. These parameters are obtained based on the relationships proposed in [2] to accommodate the hysteresis of the numerical modeling with the experimental one. The weak RC frames were retrofitted with the basis rehabilitation target by the Iranian rehabilitation Guidelines [3], signifying that the performance level of the structure is life safety (LS) under the design seismic risk (0.25 g). Also, for better evaluation of the retrofitting methods, retrofitting was conducted at two higher levels.
Conclusions
The results of the nonlinear dynamical analysis showed that shear walls can reduce the inter-story drift ratios significantly more than CFRP sheets do. The results of the cost-benefit analysis revealed that retrofitting with the CFRP sheets is a more preferable method than retrofitting with the shear walls in terms of the economic approach, especially for the shorter height structure (5-story frames). It is because the cost of executing shear walls and shear wall foundations is very expensive. By increasing the structural height (from 5 to 8 and 15 stories), CFRP sheets outperformed shear walls, while for the 15-story frame, adding the CFRP sheets was a better solution than adding the shear walls. For high- and middle-height structures (8- and 15-story frames), the differences in the cost-benefit ratio of the two methods were ignorable. The CFRP sheets further reduced the exceedance probability of damages at low earthquake hazard levels, while shear walls further reduced the probability of damage occurrence and damage exceedance (especially high-performance levels such as collapse prevention). This is especially the case for higher-rise structures where the collapse probabilities are higher than for the shorter structures, leading to a close cost-benefit ratio of the two retrofitting methods.
References
1. Valles, R.E., et al. (2009) IDARC2D Version 7.0: a Computer Program for the Inelastic Damage Analysis of Buildings. NCEER, State Univ. of New York at Buffalo, technical report MCEER-09-0006.
2. Bakhshi, A. and Asadi, P. (2013) Probabilistic evaluation of seismic design parameters of RC frames based on fragility curves. Scientia Iranica, 20(2), 231-241.
3. Strategic Oversight Deputy, Technical System Affairs (2013) Guideline for Seismic Rehabilitation of Existing Buildings, Publication No. 360, (1st revision) (in Persian).

کلیدواژه‌ها [English]

  • Retrofitting
  • Fragility Curve
  • Damage Cost
  • Cost-Benefit Analysis
  • Carbone Fiber Reinforcement Polymer
  • Shear Wall
  1. Maheri, M. (2005) Recent Advances in Seismic Retrofit of RC Frames. Asian Journal of Civil Engineering (Building & Housing), 6(5), 373-391.
  2. Sokkary, H. and Galal, K. (2008) Analytical Investigation of the Seismic Performance of RC Frames Rehabilitated Using Different Rehabilitation Techniques. Engineering Structures, 31, 1955-1966.
  3. Mowrtage, W. (2014) Simple Strengthening Techniques and New Technologist for Seismic Safety of Existing Building: Recent Research and Applications in Turkey. International Burdur Earthquake & Environment Symposium (IBEES2015) Uluslararası Burdur Deprem ve Cevre Sempozyumu 7-9 May 2015, Mehmet Akif Ersoy University, Burdur-Türkiye.
  4. Melani, A., Khare, R.K., Dhakal, R.P. and Mander, J.B. (2015) Seismic risk assessment of low rise RC frame structure. Structures, 5, 13-22.
  5. Choi, S.V. (2017) Investigation on the seismic retrofit positions of FRP jackets for RC frames using multi-objective optimization. Composites Part B: Engineering, 123(15), 34-44.
  6. Seifi, A., Mohammad, A., Mohammad, S., and Zareian, S. (2017) Improving seismic performance of old-type RC frames using NSM technique and FRP jackets. Engineering Structures, 147(15), 705-723.
  7. Hueste, M. and Bai, J. (2007) Seismic Retroï‌t of a Reinforced Concrete Fat-Slab Structure: Part II: Seismic Fragility Analysis. Engineering Structures, 29, 1178-1188.
  8. Padgett, J.E., Dennemann, K., and Ghosh, J. (2009) Risk-Based Seismic Life-Cycle Cost–Beneï‌t (LCC-B) Analysis for Bridge Retroï‌t Assessment. Structural Safety, 32, 165-173.
  9. Wen, Y.K. and Kang, Y.J. (2001) Minimum building life-cycle cost design criteria. I: Methodology. Journal of Structural Engineering, 127(3), 330-337.
  10. Kyriakides, N.C., Chrysostomou, C.Z., Tantele, E.A., and Votsis, R.A. (2015) Framework for the derivation of analytical fragility curves and life cycle cost analysis for non-seismically designed buildings. Soil Dynamics and Earthquake Engineering, 78, 116-126.
  11. Tarfan, S., Banazadeh, M., and Esteghamati, M.Z. (2018) Probabilistic seismic assessment of non-ductile RC buildings retrofitted using pre-tensioned aramid fiber reinforced polymer belts. Composite Structures, 208, 865-878.
  12. Valente, M., and Milani, G. (2018) Alternative retrofitting strategies to prevent the failure of an under-designed reinforced concrete frame. Engineering Failure Analysis, 89, 271-285.
  13. Sousa, L., and Monteiro, R. (2018) Seismic retrofit options for non-structural building partition walls: Impact on loss estimation and cost-benefit analysis. Engineering Structures, 161, 8-27.
  14. Office of Technical Affairs Deputy Technical, Criteria Codification and Earthquake Risk Reduction Affairs Bureau (2006) The Guideline for Design Specification of Strengthening RC Buildings Using Fiber Reinforced Polymers (FRP), Publication No. 345 (in Persian).
  15. Hwang, H.H.M., and Huo, J.R. (1994) Generation of hazard-consistent fragility curves for seismic loss estimation studies. New York; U.S. National Center for Earthquake Engineering Research, (149) p. ilus, Tab. (Technical Report NCEER, 94-0015).
  16. ATC (1985) ATC-13, Earthquake Damage Evaluation Data for California. Redwood City, CA, pp. 492, Applied Technology Council.
  17. Permanent Committee for Revising, The Iranian Code of Practice for Seismic Resistant Design of buildings (2015) Iranian Code of Practice For seismic Resistant Design Of buildings, Standard No. 2800 (4th edition) (in Persian).
  18. Computers and Structures, Inc. (2011) CSI Analysis Reference Manual for Sap2000, ETABS, SAFE and CSiBridge. Computers and Structures, Inc., Berkeley, California, USA.
  19. Valles R.E., et al. (2009) IDARC2D version 7.0: a computer program for the inelastic damage analysis of buildings. NCEER, State Univ. of New York at Buffalo, technical report MCEER-09-0006.
  20. Bakhshi, A. and Asadi, P. (2013) Probabilistic evaluation of seismic design parameters of RC frames based on fragility curves. Scientia Iranica, 20(2), 231-241.
  21. Sivaselvan, M.V. and Reinhorn, A.M. (1999) Hysteretic Models for Cyclic Behavior of Deteriorating Inelastic Structures, University at Buffalo, State University of New York Department of Civil, Structural and Environmental Engineering, Ketter Hall Buffalo, New York 14260, Technical Report MCEER-99-0018.
  22. Valles, R.E., Reinhorn, A.M., Kunnath, S.K., Li, C. and Madan, A. (1996) IDARC2D, Version 4.0: A Computer Program for the Inelastic Damage Analysis of Buildings. State University of New York Department of Civil, Structural and Environmental Engineering Ketter Hall Buffalo, New York 14260, Technical Report NCEER-96-0010.
  23. Strategic Oversight Deputy, Technical system affairs, (2013) Guideline for Seismic Rehabilitation of Existing Buildings. Publication No. 360, (1st revision) (in Persian).
  24. Mahini, S.S., and Ronagh, H.R. (2009) Strength and ductility of FRP web-bonded RC beams for the assessment of retrofitted beam-column joints. Composite Structures, 92(6), 1325-1332.
  25. SeismoSoft (2004). SeismoSignal v.3.1-A computer program for the signal processing of strong-motion data. Available from URL: http://www.seismosoft.com.
  26. Chopra, A.K., and Chintanapakdee, C. (2003) Inelastic Deformation Ratios for Design and Evaluation of Structures: Single-Degree-of-Freedom Bilinear Systems. Earthquake Engineering Research Center, University of California, Berkeley, UCB/EERC 2003-09.
  27. Federal Emergency Management Agency (2000) Prestandard and Commentary for the Seismic Rehabilitation of Buildings, FEMA-356, Washington, DC.