مقایسه اثر زلزله‌های حوزه نزدیک و زلزله‌های حوزه دور بر پاسخ لرزه‌ای سیستم ‌خاک-شمع-سازه

نوع مقاله: علمی - پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد مهندسی ژئوتکنیک، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره)

2 استادیار، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره)

چکیده

حرکات لرزهای ثبت شده در مناطق نزدیک گسل که جهت گسیختگی گسل به سمت آنها می‌باشد با حرکات مشاهده شده در مناطق دور از گسل بسیار متفاوت هستند. در این تحقیق برای مقایسه اثر زلزله‌های حوزه نزدیک و زلزله‌های حوزه دور بر روی یک سیستم خاک، گروه شمع و سازه از مدل‌سازی به روش اجزاء محدود استفاده شده، و امکان رفتار غیرخطی برای سازه در مدل‌سازی لحاظ شده است. جهت مدل‌سازی خاک دانه‌ای(ماسه) از مدل هایپوپلاستیک Von Wolffersdorff با در نظر گرفتن مفهوم کرنش بین‌دانه‌ای استفاده شده است. 5 رکورد زلزله حوزه نزدیک و 5 رکورد زلزله حوزه دور، که روی سنگ سخت ثبت شده‌اند، به مدل اعمال شده‏اند. نتایج نشان می‌دهند که با عبور امواج زلزله از خاک، زمان تناوب اصلی لایه خاک در اثر تغییرشکل‏های غیرخطی افزایش می‏یابد. همچنین در زلزله‌های حوزه نزدیک به دلیل حرکات پالس-شکل زمین، یک پالس تغییرمکان در شمع ایجاد می‏شود. درصورتی‌که در زلزله‌های حوزه دور به دلیل توزیع یکنواخت‏تر انرژی در طول مدت زلزله، ماهیت پاسخ تغییرمکان شمع متفاوت است. در زلزله‌های حوزه نزدیک به ازای یک PGA ثابت مقادیر تغییرمکان‌ نسبی شمع با مقادیرPGVو همچنین PGD رکوردها دارای همبستگی مثبت می‏باشند، ولی در هنگام اعمال زلزله‌های حوزه دور این همبستگی دیده نمی‌شود.

کلیدواژه‌ها


عنوان مقاله [English]

Comparison between the Effects of Near- and Far-Fault Ground Motions on the Seismic Response of a Soil-Pile-Structure System

نویسندگان [English]

  • Saeed Abbasi Karafshani 1
  • Alireza Ardakani Ardakani 2
  • Mansoor Yakhchalian 2
1 MSc student in Geotechnical Engineering, Faculty of Engineering & Technology, Imam Khomeini International University
2 Assistant professor, Faculty of Engineering & Technology, Imam Khomeini International University
چکیده [English]

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to compare the effects of near- and far-fault ground motions on a system consisting of soil, pile group and structure, considering the possibility of non-linear behavior for the structure. The Von Wolffersdorff hypoplastic model with intergranular strain concept is applied for modeling of granular soil (sand). Five fault-normal near-fault ground motion records and five far-fault ground motion records, recorded on rock, are applied to the model. The results show that when seismic waves pass through the soil layer, the fundamental period of the soil layer lengthens, due to non-linear deformations. Also, in near-fault pulse-like ground motions a displacement pulse is generated in the pile response. Whereas, in the far-fault ground motions, due to the more uniform distribution of energy during the record, such pulse-like displacements are not observed in the pile response. Based on the obtained results, for a constant PGA, there are positive correlations between the values of maximum pile displacement, and PGD and PGV values of near-fault ground motion records. But such correlations are not observed in the case of far-fault ground motions.

کلیدواژه‌ها [English]

  • Near-fault ground motions
  • Far-fault ground motions
  • Soil-pile-structure interaction
  • Hypoplasticity
  • Finite element method

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