بررسی اهمیت خروج از مرکزیت اتفاقی در طراحی لرزه‌ای ساختمان‌های فولادی با سیستم دوگانه تحت اثر زلزله‌های حوزه دور و نزدیک گسل

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، دانشگاه صنعتی سهند، تبریز، ایران

2 شهر جدید سهند- دانشگاه صنعتی سهند- دانشکده مهندسی عمران

چکیده

در پی تشدید پاسخ لرزه‌ای ساختمان‎ها در اثر پیچش، به منظور درنظرگیری عواملی که تاثیر آن‎ها در طراحی ساختمان به صراحت در پاسخ پیچشی لحاظ نمی‌گردند، آیین‎نامه‎ها ضابطه‎ای را با نام خروج از مرکزیت طراحی اتفاقی معرفی می‎نمایند. در این مطالعه، تاثیر ضابطه خروج از مرکزیت طراحی اتفاقی استاندارد زلزله 2800 در طراحی لرزه‎ای ساختمان‎های فولادی متقارن و نامتقارن 5 طبقه، دارای سیستم باربر جانبی دوگانه، در دو حالت پیچشی سخت و نرم با خروج از مرکزیت‎های جرمی اولیه 0.10b و 0.20b که b اندازه بعد پلان ساختمان می‌باشد، مورد بررسی قرار می‌گیرد. بدین منظور، ساختمان‎ها تحت تحلیل‎های تاریخچه زمانی غیرخطی با بکار‎گیری سه دسته رکورد زلزله حوزه دور و نزدیک گسل پالس‌دار و بدون پالس قرار می‎گیرند. در مرحله اول، تاثیر خروج از مرکزیت طراحی اتفاقی روی ساختمان‎های متقارن و نامتقارن بررسی می‌گردد. در مرحله دوم، ساختمان‎های طراحی نشده و طراحی شده برای خروج از مرکزیت طراحی اتفاقی با اعمال خروج از مرکزیت اتفاقی واقعی و جابجا نمودن مرکز جرم به مقدار 5 درصد بعد ساختمان در دو جهت X و Y تحت تحلیل‎های تاریخچه زمانی غیرخطی قرار می‎گیرند. نتایج نشان می‌دهند که ضابطه خروج از مرکزیت طراحی اتفاقی تاثیر اندکی در پاسخ‎های لرزه‎ای غیرالاستیک دارد و می‎تواند برای ساختمان‎های پیچشی سخت نادیده گرفته شود. از طرف دیگر، خروج از مرکزیت جرمی اتفاقی تاثیر بیشتری در ساختمان‎های پیچشی نرم دارد، ولی ضابطه خروج از مرکزیت طراحی اتفاقی تاثیر اندکی روی کاهش پاسخ‎های لرزه‎ای دارد. بنابراین، ضابطه خروج از مرکزیت طراحی اتفاقی برای ساختمان‎های پیچشی نرم نیاز به اصلاح دارد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The importance of accidental design eccentricity in seismic design of steel buildings with dual system under the effect of far- and near-fault ground motions

نویسندگان [English]

  • Mohammad Reza Vafidsarkari 1
  • Mehdi Poursha 2
1 Sahand University of Technology
2 Sahand University of Technology
چکیده [English]

Seismic responses of buildings are amplified due to torsion. To account for the effects that cause torsion and are not considered in the design process of buildings, the seismic codes introduce “accidental design eccentricity (ADE)”. In this study, the adequacy of the Iranian Standard No. 2800 provisions about the design eccentricity was investigated. To this end, the 5-story torsionally-stiff and torsionally-flexible buildings with dual lateral load resisting system were studied. The mass eccentricity in plan-asymmetric buildings was assumed to be equal to 0.10b and 0.20b where b is the plan dimension. Nonlinear time history analyses were performed using far-field (FF), non-pulse (NP) and pulse-like (FD) near-field records for the models in two cases. In the first case, the effect of the ADE on the seismic demands of symmetric and asymmetric-plan buildings was investigated. Finally, to consider what happens when an actual accidental mass eccentricity (AME) is introduced in an already designed building, the mass center of the buildings was shifted by ±0.05b (b is the dimension of the building perpendicular to the earthquake direction) simultaneously in both directions and the buildings (with and without ADE) were analyzed for the earthquake sets described above. For the buildings investigated in this research, the results indicate that the provision related to the accidental design eccentricity has little influence (less than 10%) on the inelastic seismic responses for torsionally-stiff buildings and can be ignored. Also, the accidental mass eccentricity has more influence (maximum 38%) on the inelastic seismic responses of torsionally-flexible buildings but the accidental design eccentricity has less influence on the reduction of seismic responses. Therefore, it seems that the accidental design eccentricity needs to be modified for torsionally-flexible buildings.

کلیدواژه‌ها [English]

  • Accidental eccentricity
  • near-field
  • forward directivity
  • tirsionally-stiff buildings
  • tirsionally-flexible buildings

مراجع

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نشریه مهندسی عمران امیرکبیر
دوره 52، شماره 7
مهر 1399
صفحه 1705-1728

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