بررسی پاسخ های لرزه ای ساختمان های جداسازی شده پایه تحت اثر زلزله‌های حوزه‌ی نزدیک گسل

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه صنعتی سهندتبریز، تبریز، ایران

چکیده

به علت تاثیر قابل توجه زلزله  ا بر ساختمان های واقع در مناطق نزدیک گسل، در این مطالعه سعی می شود که رفتار قاب های خمشی فولادی جداسازی شده ی پایه تحت اثر زلزله های حوزه نزدیک گسل با استفاده از تحلیل تاریخچه زمانی غیرخطی مورد بررسی قرار گیرد. بدین منظور 2قاب خمشی فولادی با ارتفاع متوسط ( 9و 12طبقه) با استفاده از جداسازهای لاستیکی با هسته ی سربی 1(LRB) جداسازی می شوند. برای هر سازه سه نوع جداساز با سختی های مختلف، شامل جداسازهای سخت) H)، جداسازهای متوسط (N ) و جداسازهای نرم (S) در نظر گرفته می شود. به منظور انجام تحلیل تاریخچه زمانی غیرخطی از چهار گروه 7تایی شتاب نگاشت استفاده می شود. یک گروه شامل 7رکورد زلزله ی حوزهی دور از گسل 2(FF) بوده و سه گروه دیگر، رکوردهای حوزه ی نزدیک گسل هستند که نمایندهی سه ویژگی مهم این زلزله ها شامل جهت پذیری رو به جلو ( ،(FD) 3حرکت پرتابی 4(FS) ، و زلزله های نزدیک گسل فاقد پالس 5می باشند. پاسخ های لرزهای مختلف تحت اثر چهار گروه متفاوت زلزله بررسی می شود و اثر سختی جداساز و پریود پالس (TP ) زلزله های نزدیک گسل روی پاسخ های لرزهای مورد مطالعه قرار می گیرد. نتایج نشان می دهد که تغییر سیستم جداسازی از نوع سخت به نوع متوسط و نرم (افزایش میرایی و زمان تناوب) باعث کاهش نیازهای لرزهای می شود. همچنین قاب های با جداسازی نوع نرم (S )( میرایی بیشتر) پاسخ تغییرمکان نسبی طبقات مناسب تری را به ازای مقادیر مختلف TPارائه می دهند، اما حساسیت پاسخ قاب های جداسازی شده با جداساز نوع سخت (میرایی پایین) به پریود پالس TPزلزله های نزدیک گسل بیشتر می باشد که عملکرد چنین قاب هایی را غیرقابل اطمینان می کند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Investigation of the Seismic Responses of Base isolated Buildings Under the Influence of Near field Round Motions

نویسندگان [English]

  • S. Haseli
  • M. Poursha
Department of Civil Engineering, Sahand University of Technology, Tabriz, Iran
چکیده [English]

Due to destructive effects of near-field earthquakes on building structures, this paper attempts to investigate the seismic behavior of base-isolated building frames under the effect of near-field ground motions using the non-linear time history analyses (NLTHAs). For this purpose, two steel moment-resisting medium-rise frames including 9 and 12-story ones were isolated using the lead-rubber base isolation system considering three levels of stiffness i.e. Hard (H), Normal (N) and Soft (S) isolators. Non-linear time history analyses (NLTHAs) were conducted using different sets of near-field ground motions with forward directivity, fling step and no pulse characteristics. Also, for the purpose of comparison, the NLRHA was carried out using a set of far-field ground motion records. The effect of isolator stiffness under different types of ground motions as well as the effect of pulse period on the seismic responses is scrutinized. The results showed that the change in the stiffness of isolation system from hard type to soft and moderate types (that increases the damping and period of the structure) reduces the seismic demands of the structure. Also, the story drifts of base-isolated building frames with soft isolator (more damping) are smaller than those with hard and moderate types for different values of pulse period, Tp. On the other hand, the sensitivity of the responses of base-isolated building frames with hard isolators (low damping) to pulse period is large.

کلیدواژه‌ها [English]

  • Base Isolation
  • Near-Fault Earthquakes
  • Fling-Step Effect
  • Forward-Directivity Effect
  • Non-linear Time History Analyses (NLTHAs)

مراجع

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نشریه مهندسی عمران امیرکبیر
دوره 50، شماره 3
مرداد و شهریور 1397
صفحه 579-596

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