ارزیابی پارامترهای لرزه‌ای قاب خمشی فولادی ویژه به روش نسبت حاشیه ایمنی فروریزش(CMR) (ضریب اصلاح R و ضریب اضافه مقاومت Ω_0 )

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه علم و صنعت، تهران، ایران

چکیده

این مقاله برآن است که پارامترهای لرزهای طراحی قابهای فولادی خمشی ویژه ارائه شده در استاندارد 2800ایران را بطور کلی مورد ارزیابی قرار دهد. بدین منظور شانزده قاب (12 ،8 ،6 ،4طبقه در چهار گروه روی چهار نوع خاک) بر اساس استاندارد 2800طراحی و با روش دینامیکی افزایشی ( IDA)تحلیل غیر خطی انجام و منحنی شکست هر یک تهیه گردیده است. تحلیلها با برنامه کامپیوتری OPENSEES انجام گردیده که درآن اثر زوال سختی و مقاومت اعضا رعایت شده است. از 22زوج شتابنگاشت کلی حوزه دور ارائه شده توسط FEMA_P695برای محاسبه میانه شکست قابها استفاده شده و با ضریب شکل طیفی (SSF )سازگار با زلزله نادر منطقه تدوین شده است. پارامترهای لرزهای شامل ضریب رفتار ( R)و ضریب اضافه مقاومت (Ω0 )با دو روش برای هر گروه محاسبه شده است. یکی با استفاده از ضوابط ( FEMA_P695بر مبنای اینکه اپسیلون بهعنوان پارامتر شکل طیفی زلزله است) و روش دیگری بر مبنای تعریف فیزیکی شکل طیفی ارائه شده است. نتایج این مطالعه نشان میدهد که هر چهار گروه از دیدگاه ضوابط FEMA_P695قابل پذیرش ولی گروههای 2و 3(ساخته شده روی خاکهای بترتیب نوع 2و 3), با ضوابط روش دیگر قابل قبول نمی باشند. امید است تمامی پارامترهای طراحی لرزهای در استاندارد 2800با روشهای جاری تحلیلی مورد ارزیابی قرار داده شوند.
 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic Design Parameters Assessment of Special Steel Moment Resisting Frames Using the Collapse Margin Ratio (CMR) Method

نویسندگان [English]

  • A. Nicknam
  • M. Farhangdoust
  • A. Mazarei
  • M. Ganjvar
Civil Engineering Department, Iran University of Science and Technology, Tehran, Iran
چکیده [English]

This research intends to quantitatively evaluate the seismic parameters of special steel resisting moment frames designed via the prescribed values in the Iran standard No. 2800. Sixteen designed frames having 4, 6, 8, and 12 stories and grouped into four types are dynamically non-linearly analyzed by means of OPENSEES software incorporating the element stiffness degradation. The general far-fault 22 record pairs presented by FEMA_P695 is used in the process of preparing the frame’s fragility curves where are localized with multiplying their medians by corresponding predicted spectral shape factors (SSF). The frame’s seismic parameters (R factor and over-strength factor) are calculated using two methods; FEMA_P695 criteria, developed on the basis of epsilon as the spectral shape parameter, and the proposed approach, developed on the actual definition of spectral shape parameter. The results of this study showed that use of FEMA_P695’s rules end up with acceptable groups’ seismic parameters, opposed to those groups where have been associated with rock and soft soil conditions and judged by the other approach. It is expected that the whole seismic parameters presented in the standard No. 2800 will be evaluated based on the currently used analytical methods in the near future.

کلیدواژه‌ها [English]

  • IDA method
  • Fragility curve
  • ACMR
  • R Factor
  • Over-Strength Factor
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