تأثیر زلزله‌های پی‌درپی در ترتیب وقوع و محل تشکیل مفاصل پلاستیک ساختمان‌های بتن‌آرمه

نوع مقاله : Articles

نویسندگان

1 گروه مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

2 مرکز تحقیقات ژئوتکنیک لرزه‌ای و بتن توانمند، گروه مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

چکیده

در بسیاری از آیین­نامه­های ساختمانی ضوابط طراحی بر اساس لرزش اصلی بوده و اثرات پس­لرزه در تحلیل و طراحی ساختمان در نظر گرفته نمی‌شود. تجربه وقوع زمین‌لرزه‌های گذشته نشان داده که وقوع پس­لرزه می­تواند تأثیر بسزایی در افزایش مقدار جا­به­جایی سازه، نحوه تشکیل مفاصل پلاستیک، تغییر سطح عملکرد سازه و گاهی انهدام سازه داشته باشد. لذا در این تحقیق مطالعه وسیعی بر روی پاسخ غیرخطی رده‌های مختلف سازه‌ای اعم از کوتاه‌مرتبه، میان‌مرتبه و بلندمرتبه (ساختمان‌های 4، 7، 10، 13، 16 و 20 طبقه) بتن­آرمه قاب خمشی تحت اثر هفت رکورد منفرد (فقط لرزش اصلی) و هفت رکورد دارای پس­لرزه (لرزش اصلی به همراه پس‌لرزه) انجام شده است. میانگین دوران پلاستیک و نحوه تشکیل آنها و همچنین چرخش طبقه و سطح عملکرد سازه تحت تحلیل تاریخچه زمانی غیرخطی محاسبه و با هم مقایسه شد. نتایج نشان می­دهد تحت اثر پس­لرزه ساختمان دچار خرابی­های شدیدی شده و تعداد مفاصلی که از محدوده LS عبور می­کند به‌طور قابل‌توجهی افزایش می­یابد به‌طوری‌که این مقدار در ساختمان 13 طبقه 31 برابر شده به‌گونه‌ای که بعد از وقوع زمین‌لرزه در آستانه فروریزش قرار گرفت. در همه سازه‌ها به‌جز ساختمان 4 طبقه، تحت رکورد زلزله‌ی دارای پس‌لرزه، مفاصل پلاستیک در ستون‌های بعضی از طبقات تشکیل شد. همچنین مقدار میانگین دوران پلاستیک در ساختمان 20 طبقه در طبقه دهم تا 25 درصد نسبت به سایر طبقات افزایش داشته است. مقدار چرخش طبقه به‌طور قابل‌توجهی تحت اثر پس­لرزه افزایش داشت به‌طوری‌که در ساختمان 10 طبقه، در طبقه چهارم این مقدار تا 41/9 برابر شده است.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Mainshock-Aftershock Seismic Sequences on the Occurrence Order and Position of Plastic Hinges

نویسندگان [English]

  • Mohammad Baniasadi 1
  • Alireza Mortezaei 2
1 Semnan Branch, Islamic Azad University, Semnan, Iran
2 Seismic Geotechnical and High Performance Concrete Research Centre, Civil Engineering Department, Semnan Branch, Islamic Azad University, Semnan, Iran
چکیده [English]

Previous earthquakes have shown that a strong ground motion is followed by some aftershocks that are smaller than the main shock, but often produce moderate to high aftershocks in the affected areas. Hence, the structures constructed in seismic areas are not only affected by a single seismic event, but this event also includes foreshocks, main shock and aftershocks. For example, the 2012 East Azerbaijan earthquake (August 21, 2012), with a magnitude of Mw = 6.4 occurred in the northeast of Tabriz, had an aftershock with a magnitude of Mw = 6.3 that happened approximately 11 minutes later. It is known that aftershocks can cause significant failure to the structures damaged by mainshock ground motions. In other words, during aftershocks, there are structures that have already been damaged by an earthquake and have not yet been repaired, which may be damaged or collapsed under the aftershock seismic event. Literature review shows that most existing codes are limited to choose a single event called "design earthquake", while the effects of aftershock earthquakes have been ignored. Despite the qualitative knowing of this issue, limited studies have been reported in the past studies on sequence earthquakes. The plastic hinge area in reinforced concrete buildings is an area where an RC member experiences a moderate to severe plastic deformation under the moderate to strong ground motions. The occurrence order and position of plastic hinges plays a key role in the seismic rehabilitation of old buildings as well as the design of new structures. Contrary to the subject importance, most studies have been limited to the steel structures, and no studies have been conducted on the occurrence order and position of plastic hinges in the reinforced concrete buildings under the mainshock-aftershock seismic sequences. Therefore, in this paper, three-dimensional models with 4, 7, 10, 13, 16, and 20 stories are evaluated under the seven single and seven mainshock-aftershock earthquake records by nonlinear time-history analysis. The formation and average rotation of plastic hinges as well as the performance level of the structures are calculated and compared by nonlinear time history analysis. The results show that the buildings suffered serious damage under the aftershock earthquakes. Number of plastic hinges that pass through LS level increase significantly, so that this number is 31 times in the 13-story building and the building collapse after mainshock earthquake. In all the structures except the 4-story building, under the mainshock-aftershock earthquake records, plastic hinges are formed in the columns of some stories.

کلیدواژه‌ها [English]

  • Nonlinear Time History Analysis
  • Single Earthquake
  • Aftershock
  • Plastic Hinge
  • Story Rotation
  1. EERI (2012) Learning from Earthquakes: the Mw 6.4 and Mw 6.3 Iran Earthquakes of August 11, 2012. EERI Special Earthquake Report. Earthquake Engineering Research Institute.
  2. Dreger, D. (1997) The large aftershocks of the Northridge earthquake and their relationship to mainshock slip and fault-zone complexity. Bulletin of the Seismological Society of America, 87(5), 1259–1266.
  3. EERI (2010) Learning from Earthquakes: The Mw 8.8 Chile Earthquake of February 27, 2010. EERI Special Earthquake Report. Earthquake Engineering Research Institute.
  4. Elnashai, A.S., Gencturk, B., Kwon, O.S., AlQadi, I.L., Hashash, Y., Rosesler, J.R., Kim, S.J., Jeon, S.H., Dukes, J., Valdivia, A. (2010) The Maule
  5. (Chile) Earthquake of February 27, 2010- Consequence Assessment and Case Studies. MAE Center Report No. 10-04, Urbana, IL.
  6. Abdelnaby, A.E., Elnashai, A.S. (2012) Response of degrading reinforced concrete systems subjected to replicate earthquake ground motions. 15WCEE, LISBOA.
  7. Kam, W.Y., Pampanin, S. (2011) The seismic performance of RC buildings in the 22 February 2011 Christchurch earthquake. Structural Concrete, 12, 223–233.
  8. Wang, G., Wang, Y., Lu, W., Yan, P., Zhou, W., and Chen, M. (2017) Damage demand assessment of mainshock-damaged concrete gravity dams subjected to aftershocks. Soil Dynamics and Earthquake Engineering, 98, 141-154.
  9. Zhai, C.H., Zheng, Z., Li, S., and Xie, L.L. (2015) Seismic analyses of a RCC building under mainshock–aftershock seismic sequences. Soil Dynamics and Earthquake Engineering, 74, 46-55.
  10. Shin, M. and Kim, B. (2017) Effects of frequency contents of aftershock ground motions on reinforced concrete (RC) bridge columns. Soil Dynamics and Earthquake Engineering, 97, 48-59.
  11. Fragiacomo, M., Amadio, C., and Macorini, L. (2004) Seismic response of steel frames under repeated earthquake ground motions. Engineering Structures, 26, 2021–2035.
  12. Lee, K. and Foutch, D.A. (2004) Performance evaluation of damaged steel frame buildings subjected to seismic loads. Journal of Structural Engineering, 130(4), 588-599.
  13. Hatzigeorgiou, G.D., Beskos, D.E. (2009) Inelastic displacement ratios for SDOF structures subjected to repeated earthquakes. Engineering Structures, 31, 2744-2755.
  14. Hatzigeorgiou, G.D. and Liolios, A.A. (2010) Nonlinear behaviour of RC frames under repeated strong ground motions. Soil Dynamics and Earthquake Engineering, 30, 1010-1025.
  15. Ruiz-Garcia, J. (2012) Mainshock-aftershock ground motion features and their influence in building’s seismic response. Journal of Earthquake Engineering, 16, 719-737.
  16. Burton, H.V., Sreekumar, S., Sharma, M., and Sun, H. (2017) Estimating aftershock collapse vulnerability using mainshock intensity, structural response and physical damage indicators. Structural Safety, 68, 85-96.
  17. Wen, W., Zhai, C., Ji, D., Li, S., and Xie, L. (2017) Framework for the vulnerability assessment of structure under mainshock-aftershock sequences. Soil Dynamics and Earthquake Engineering, 101, 41-52.
  18. Jeon, J.S., DesRoches, R., and Lee, D.H. (2016) Post-repair effect of column jackets on aftershock fragilities of damaged RC bridges subjected to successive earthquakes. Earthquake Engineering and Structural Dynamics, 45, 1149–1168.
  19. Song, R., Li, Y., and Van de Lindt, J.W. (2016) Loss estimation of steel buildings to earthquake mainshock–aftershock sequences. Structural Safety, 61, 1-11.
  20. Trevlopoulos, K. and Gueguen, P. (2016) Period elongation-based framework for operative assessment of the variation of seismic vulnerability of reinforced concrete buildings during aftershock sequences. Soil Dynamics and Earthquake Engineering, 84, 224-237.
  21. Nazari, N., Van de Lindt, J.W., and Li. Y. (2015) Quantifying changes in structural design needed to account for aftershock hazard. Journal of Structural Engineering, 141(11), 04015035.
  22. Han, R., Li, Y., and Van de Lindt, J.W. (2015) Assessment of seismic performance of buildings with incorporation of aftershocks. Journal of Performance of Constructed Facilities, 29(3): 04014088.
  23. Han, R., Li, Y., and Van de Lindt, J.W. (2015) Impact of aftershocks and uncertainties on the seismic evaluation of non-ductile reinforced concrete frame buildings. Engineering Structures, 100, 149-163.
  24. Eurocode 2 (2004) Design of Concrete Structures - Part 1: General Rules and Rules for Buildings.
  25. European Committee for Standardization (CEN), Brussels, Belgium, 225p.
  26. American Concrete Institute (2014) Building Code Requirements for Structural Concrete (ACI 318-14), ACI Committee 318, USA, 503p.
  27. CSA (Canadian Standards Association) (2014) Design of Concrete Structures. CSA-A23.3. National Standard of Canada, Toronto.
  28. AS (Australia Standards) (2009) Australian Standard for the Design of Reinforced Concrete. AS 3600, Homebush, NSW, Australia.
  29. BSI (British Standard Institute) (2005) Structural Use of Concrete. Code of Practice for Design and Construction. BS 8110BSI, London.
  30. Moehle, J. (2015) Seismic Design of Reinforced Concrete Buildings. McGraw-Hill Education.
  31. Mortezaei, A. (2013) Plastic hinge length of RC columns considering soil-structure interaction. Earthquakes and Structures, 5(6), 679-702.
  32. SAP2000, Integrated software for Structural analysis & design, Computers & structures, Inc., Berkeley, California, USA, V. 18.1.1.
  33. Ministry of Housing and Urban Development (2013) National Building Regulation, Part 9: Design and Construction of RC Buildings. Office of National Building Regulations, Tehran, Iran.
  34. Building and Housing Research Center (2015) Standard NO. 2800-15: Iranian Code for Seismic Resistant Design of Building. 4th edition.
  35. FEMA-356 (2000) Prestandard and Commentary for the Seismic Rehabilitation of Buildings American Society of Civil Engineers.
  36. Pavel, F. and Lungu, D. (2013) Correlations between frequency content indicators of strong ground motions and PGV. Journal of Earthquake Engineering, 17(4), 543-559.
  37. Li, Q. and Ellingwood, B.R. (2007) Performance evaluation and damage assessment of steel frame buildings under main shock–aftershock earthquake sequences. Earthquake Engineering and Structural Dynamics, 36, 405–27.
  38. Douglas, J. and Halldorsson, B. (2010) Using Aftershock Data When Deriving Earthquake Ground-Motion Prediction Equations. Earthquake Engineering Research Centre – University of Iceland.