مهندسی سازه و ساخت

مهندسی سازه و ساخت

ارزیابی احتمالاتی خطر فروریزش در یک سازه جداسازی‌شده لرزه‌ای

نوع مقاله : علمی - پژوهشی

نویسندگان
1 دانشجوی دکتری، گروه مهندسی عمران، دانشکده مهندسی، دانشگاه فردوسی، مشهد، ایران
2 دانشیار، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران
چکیده
این پژوهش به بررسی فروریزش احتمالاتی سازه‌ی مبنا با جداگر لرزه‌ای و کفایت ضوابط طراحی موجود در آیین‌نامه ASCE 7-22 با تمرکز بر شکست سیستم جداساز می‌پردازد. شبیه‌سازی‌ها در نرم‌افزار OpenSEESانجام شده و در آن از جداگر اصطکاکی پاندولی (FPS) و جداگر اصطکاکی پاندولی سه‌سطحی (TFPI) استفاده گردیده است. قابلیت اطمینان ظرفیت جابجایی سیستم جداگر تحت اثر شتاب‌نگاشت‌های میدان‌نزدیک و میدان‌دور، بر اساس ضوابط FEMA P695، ارزیابی شده است. همچنین، از روش تحلیل دینامیکی افزایشی (IDA) و فرآیندهای FEMA P695 برای تحلیل فروریزش احتمالاتی جداگرها و ارزیابی کفایت ضوابط موجود در آیین‌نامه ASCE 7-22 بهره گرفته شده است. یافته‌ها نشان می‌دهد که طراحی‌های مبتنی بر ضوابط ASCE 7-22 اغلب نمی‌توانند الزامات قابلیت‌اطمینان را برآورده کنند. بررسی‌ها تأکید دارند که برای دستیابی به اهداف قابلیت‌اطمینان در گروه‌های خطر مختلف، ظرفیت‌ جابجایی جداگر باید به‌طور قابل توجهی فراتر از مقادیر محاسبه‌شده طبق آیین‌نامه افزایش یابد. این موضوع به‌ویژه در مورد شتاب‌نگاشت‌های میدان‌نزدیک که دارای رفتار ضربه‌مانند و لرزش‌های پالس‌گونه هستند اهمیت بیشتری پیدا می‌کند. علاوه بر این، نتایج پژوهش نشان می‌دهد که اثرات پیچشی به‌عنوان یکی از عوامل کلیدی در افزایش احتمال فروریزش سیستم جداگر عمل می‌کنند. نادیده گرفتن این اثرات می‌تواند به تخمین‌های نادرست و کاهش ایمنی سازه منجر شود. یافته‌های این تحقیق بر ضرورت بازنگری در شیوه‌های طراحی لرزه‌ای کنونی تأکید کرده و نشان می‌دهد که طراحی‌های فعلی برای دستیابی به ایمنی و قابلیت اطمینان مطلوب نیازمند اصلاحات جدی هستند. این اصلاحات می‌توانند شامل افزایش ظرفیت‌های جداگر، استفاده از روش‌های پیشرفته تحلیل و در نظر گرفتن دقیق اثرات میدان‌نزدیک و پیچش باشند.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Probabilistic Evaluation of Collapse Risk for a Base-Isolated Structure

نویسندگان English

Ali Akbar Shaikhzadeh 1
Abbas Karamodin 2
1 PhD. Candidate, Department of Civil Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Iran
2 Associate Professor, Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
چکیده English

This study investigates the probabilistic collapse behavior of a benchmark base-isolated structure, focusing specifically on the failure mechanisms of its isolation system. Numerical simulations were performed using the OpenSEES software, incorporating both traditional Friction Pendulum Systems (FPS) and advanced Triple Friction Pendulum Isolators (TFPI) to evaluate their performance under the influence of far-field and near-fault ground motions. The assessment of displacement capacity and system reliability adheres to FEMA P695 guidelines. Furthermore, Incremental Dynamic Analysis (IDA) and FEMA P695 procedures were employed to analyse the collapse probability of isolators and to evaluate the adequacy of current seismic design practices outlined in ASCE 7-22. The findings highlight that isolators designed based on ASCE 7-22 provisions often fail to meet the reliability requirements, particularly under critical conditions. The study emphasizes the necessity for significantly increased displacement capacities of isolators to achieve reliability objectives across various risk categories. This need becomes even more pronounced in near-fault ground motions characterized by pulse-like shaking, which impose unique demands on isolator design. In addition, the results reveal the critical role of torsional effects in increasing the collapse probability of isolation systems. Neglecting these effects, even at minimum levels specified by the code, leads to underestimations of collapse risks and compromises structural safety. The findings of this research underscore the urgency of revisiting current seismic design methodologies for base-isolated structures. Improvements should include enhancing isolator capacities, adopting advanced analytical methods, and accurately accounting for the effects of near-fault motions and torsional behavior to achieve the desired levels of safety and reliability.

کلیدواژه‌ها English

probabilistic collapse
benchmark building
fragility curve
sliding isolator
FEMA P695
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  • تاریخ دریافت 29 دی 1403
  • تاریخ بازنگری 22 اسفند 1403
  • تاریخ پذیرش 17 فروردین 1404