بررسی تغییرات ضریب تغییرمکان غیرخطی تحت توالی لرزه‌ای

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری مهندسی زلزله، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران

2 دانشیار، دانشکده مهندسی عمران، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران

3 استادیار، دانشکده مهندسی عمران، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران

چکیده

افزایش خسارت‌های وارده به سازه‌ها در اثر وقوع پس‌لرزه در گزارشات فنی متعددی به چشم می‌خورد. به ویژه در مورد سازه‌هایی که در زلزله اصلی دچار آسیب شده و وارد حوزه غیرخطی شده باشند. این افزایش در خسارات عموماً نتیجه افزایش تغییرمکان جانبی سازه می‌باشد. لذا اهمیت تخمین دقیق تغییرمکان جانبی سازه در حین ارزیابی لرزه‌ای آن دو چندان می‌شود. تغییرمکان جانبی هدف در روش تحلیل استاتیکی غیرخطی به کمک روابطی در آیین‌نامه‌های طراحی عملکردی محاسبه می‌شود، در حالی که تاثیر رخ دادن پس‌لرزه در آنها لحاظ نمی‌گردد. در این مطالعه نقش وقوع پس‌لرزه بر ضریب تغییرمکان غیرخطی به عنوان تاثیرگذارترین ضریب در رابطه تعیین تغییرمکان هدف، بررسی شد. نتایج نشان داد که این ضریب، افزایش قابل توجهی در اثر وقوع پس‌لرزه از خود نشان می‌دهد. پراکندگی نتایج به دست آمده منجر به بررسی سطوح خطر زلزله‌های ورودی و متعاقباً استفاده از روش مقیاس نمودن شتاب‌نگاشت‌ها گردید. به این منظور با مطالعه آماری روی نسبت شتاب ماکزیمم زلزله اصلی و پس‌لرزه متناظر با آن، طیف هدف پس‌لرزه تولید شد تا به این وسیله، پس‌لرزه‌ها به یک طیف شتاب هدف مستقل مقیاس شوند. مقایسه پاسخ‌های حاصل از مقیاس نمودن زلزله‌ها مشخص نمود که پراکندگی نتایج یک موضوع ذاتی بوده و قابلیت رفع شدن ندارد. در خاتمه با اعمال تغییرات جزئی بر روی رابطه فعلی آیین‌نامه، رابطه جدیدی برای ضریب تغییرمکان غیرخطی پیشنهاد شد و رابطه مزبور به نحوی اصلاح گردید که میانگین خطاها تا حد امکان کاهش یابد.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Mainshock-Aftershock Sequences on the Inelastic Displacement Ratios

نویسندگان [English]

  • Vahid Vahedian 1
  • Gholamreza Abdollahzadeh 2
  • Hamed Hamidi 3
1 PhD student in Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
2 Associate Professor, Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
3 Assistant Professor, Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
چکیده [English]

Past studies have shown that aftershocks can increase structural damage, especially for structures damaged in the mainshock and experienced nonlinear behavior. This damage is generally the result of increased lateral displacement of the structure and thus, it is necessary to estimate the lateral displacement of the structure under seismic evaluation accurately. Although the target displacement in the nonlinear static analysis method is calculated by means of relationships presented in performance-based design codes, the effect of the aftershock is not taken into account. In this study, the impact of aftershock on inelastic displacement ratio is considered as the most effective factor in determining the target displacement. The results showed that this ratio increases significantly due to aftershocks. The dispersion of the results led to the investigation of the hazard levels of the input earthquakes and subsequently using the scaling method of the accelerograms. For this purpose, a target aftershock spectrum was generated by a statistical study on the maximum acceleration ratio of the mainshock and its corresponding aftershocks, thereby the aftershocks scale to an independent target acceleration spectrum. Comparison of the responses from scaling revealed that dispersion in results are an inherent issue and cannot be resolved. Finally, by modifying in the current relationship of the code, a new formula has been proposed for the inelastic displacement ratio such that the mean error values were reduced as much as possible.

کلیدواژه‌ها [English]

  • inelastic displacement ratio
  • mainshock-aftershock
  • seismic sequences
  • SDOF systems
  • Nonlinear dynamic analysis
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