انتخاب مجموعه مناسب حرکات زمین برای تحلیل تاریخچه زمانی با استفاده از طیف خطر یکنواخت

نوع مقاله : علمی - پژوهشی

نویسندگان

مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه بجنورد، بجنورد، ایران

چکیده

تخمین پاسخ لرزه‌ای سازه‌ها در روش تحلیل تاریخچه‌ی زمانی تحت تأثیر رکوردهای حرکت زمین قرار دارد. با توجه به اینکه پیش‌بینی دقیق مشخصات زلزله‌های آینده امکان پذیر نیست، نحوه‌ی انتخاب رکوردهای حرکت زمین همواره به عنوان یک چالش در مهندسی زلزله مطرح بوده است. در این مطالعه، یک روش برای انتخاب مجموعه‌ی مناسب از حرکات شدید زمین با توجه به ویژگی‌های زمین شناسی و ژئوتکنیکی یک ساختگاه خاص معرفی و مورد بررسی قرار می‌گیرد. از مجموعه رکوردهایی که در این مطالعه پیشنهاد می-شود، می‌توان برای تحلیل انواع سازه‌ها بدون توجه به پریود ارتعاشی آن‌ها، حتی در ساختگاه‌هایی که در معرض حرکات پالس-گونه‌ی حوزه‌ی نزدیک قرار دارند، استفاده کرد. رکورد‌های حرکت زمین به نحوی انتخاب می‌شود که میانگین و انحراف معیار طیف‌های پاسخ آن‌ها با طیف طراحی هدف مطابقت داشته باشد. بدین منظور از طیف‌های پاسخی که بر مبنای مشخصات آماری طیف طراحی هدف شبیه‌سازی می‌شوند، استفاده می‌شود. در نظر گرفتن انحراف معیار طیف طراحی در انتخاب رکوردها، به طور مناسب عدم قطعیت ذاتی در رکوردهای زلزله را در نظر می‌گیرد. از بین حدود 300 رکورد، یک مجموعه‌ی30 تایی و یک مجموعه‌ی 7 تایی از شتاب‌نگاشت‌های زلزله که دارای بیشترین مطابقت با پارامترهای آماری طیف هدف می‌باشند، برای خاک‌های I، II و III پیشنهاد می‌‌شود. در این مطالعه، همچنین یک روش مناسب با عنوان حداقل مجموع مربعات خطاها برای تعیین ضرایب مقیاس رکوردها، مطابق ضوابط استاندارد 2800 ایران پیشنهاد می‌شود. نتایج نشان می‌دهد که استفاده از روش‌های مختلف برای مقیاس کردن رکوردها، علیرغم رعایت ضوابط آیین‌نامه می‌تواند منجر به ضرایب مقیاس مختلف برای رکوردهای مختلف و در نتیجه برآورد متفاوت از پاسخ سازه‌ها در تحلیل تاریخچه‌ی زمانی شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Selection of an appropriate ground motion records set for time history analysis using uniform hazard spectrum

نویسندگان [English]

  • Aliakbar Yahyaabadi
  • Nasrin Nomani
Department of Civil Engineering, Faculty of Engineering, University of Bojnord, Bojnord, Iran
چکیده [English]

In time history analysis of structures, it is essential to select an appropriate set of earthquake ground motions using the meaningful statistical methods. This matter is a challenge in earthquake engineering because the characteristics of future earthquakes are unpredictable. In this paper, earthquake ground motion records were selected based on the geological and geotechnical characteristics of the desired site. The record sets proposed here can be used for analyzing any structure with a desired fundamental period, even for sites that have potential to experience near-fault pulse-like events. The records were selected based on the response spectra simulated according to the statistical characteristics of the target Uniform Hazard Spectrum (UHS). The objective is that the response spectra of the selected records have the mean and standard deviation that are consistent with the corresponding values of the target UHS. In addition to the mean, the standard deviation was also considered in the records selection procedure to capture the ground motion aleatory uncertainty. Two appropriate sets of 7 and 30 records, selected from about 300 earthquake ground motion records, were suggested for each soil types of I, II, and III. Additionally, an efficient method referred to as the least sum of squared errors was developed for scaling the records with respect to the standard No. 2800 of Iran. Results demonstrate that using the different methods for scaling the records leads to various scaling factors for records, and as a consequence different structural responses using the method of time history analysis.

کلیدواژه‌ها [English]

  • Ground motions selection
  • Time history analysis
  • Mean
  • Standard deviation
  • Uniform hazard spectrum
  • Scaling
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