پیشنهاد ضرایب طراحی لرزه‌ای برای قاب فولادی مهاربندی دارای حرکت گهواره‌ای

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشگاه علوم و تحقیقات تهران

2 پژوهشگاه بین المللی زلزله و مهندسی زلزله

10.22065/jsce.2017.75463.1067

چکیده

سیستم قاب فولادی مهاربندی مرکزگرا با قابلیت برکنش کنترل شده توانایی کاهش خسارت لرزه‌ای از طریق هدایت آسیب به المان‌های میراگر قابل تعویض دارد. این مقاله به پیشنهاد ضرایب طراحی لرزه‌ای شامل ضرایب کاهش پاسخ، اضافه مقاومت و شکل پذیری برای قا‌ب‌های فولادی مرکزگرا دارای حرکت گهواره‌ای کنترل شده می‌پردازد. بدین منظور، ابتدا دوازده نمونه سیستم مرکزگرا متفاوت از نظر تعداد طبقات، محل قرارگیری قاب مهاربندی در پلان سازه و نوع خطر لرزه‌ای ساختگاه طراحی می‌گردد. مدل غیرخطی قاب دارای برکنش در نرم افزار اپنسیز به منظور شبیه‌سازی ایجاد مکانیرم در قاب و توالی خسارت در اجزای آن (کابل پس کشیده و میراگرهای جاری شونده قابل تعویض) توسعه داده شده است. ضرایب اضافه مقاومت و شکل پذیری سیستم قاب مرکزگرا با استفاده از تحلیل استاتیکی غیرخطی تعیین می‌گردد. همچنین تحلیل‌های دینامیکی فزاینده غیرخطی برای دستیابی به منحنی‌های شکنندگی حالت حدی فروریزش قاب‌های مورد مطالعه انجام می‌گیرد. با درنظرگیری عدم قطعیت موجود و اثر شکل طیفی، منحنی‌های شکنندگی اصلاح می‌گردد. با استفاده از منحنی‌های شکنندگی اصلاح شده بدست آمده، ضریب کاهش پاسخ پیشنهادی برای سیستم فولادی مرکزگرا با مقایسه نسبت حاشیه فروریزش تنظیم شده با معیارهای پذیرش ارزیابی می‌گردد. در انتها تاثیر پارمترهای مدل‌سازی و لرزه‌ای بر احتمال فروریزش سیستم بررسی می‌گردد. نتایج حاکی از آن است که قاب‌های کنترل شده مرکزگرا معیارهای پذیرش را تامین می‌نماید و طراحی این سیستم با ضرایب پیشنهادی حاشیه ایمنی کافی را در برابر فروریزش فراهم می‌آورد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Proposal for seismic design coefficients for rocking steel braced frame

نویسندگان [English]

  • Navid Rahgozar 1
  • Abdolreza S Moghadam 2
1 IAU
2 IIEES
چکیده [English]

Rocking steel braced frames are capable of reducing seismic damage through directing damage in energy dissipation elements. This paper quantifies seismic design factors for the controlled rocking self-centering braced frame including response modification, over-strength, and ductility parameters through probabilistic safety assessment methodology. For this purpose, twelve self-centering braced frames differ from the number of stories, plan location, and site class is designed. A nonlinear model is developed for the rocking braced steel frame in Opensees software to simulate the degrading and collapse of the frame and its components (post-tensioning strands and yielding replaceable damper). Over-strength and ductility factors of self-centering systems are determined using nonlinear static analysis. The incremental dynamic analysis is conducted to obtain collapse limit state fragility curves of self-centering frames. Considering total uncertainty and effects of spectral shape, the fragility curves are modified. Through modified fragility curves, proposed response modification factor is verified by comparing the adjusted collapse margin ratio with its acceptance criteria. Finally, the effects of modeling and seismic parameters on the collapse probability of the system are examined. Results indicate that controlled rocking systems are satisfied acceptance criteria and the design of the system with the proposed coefficients provide sufficient safety margin against collapse.

کلیدواژه‌ها [English]

  • Rocking braced steel frame
  • seismic design parameters
  • collapse assessment
  • collapse margin ratio
  • Fragility curve
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