بررسی اثر توزیع احتمالاتی ترک خوردگی در حالت حدی بر قابلیت اعتماد لرزه ای ساختمان های بتنی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار، دانشکده عمران، آب و محیط زیست ، دانشگاه شهید بهشتی، تهران، ایران

2 دانشجوی دکتری مهندسی زلزله، دانشکده عمران، آب و محیط زیست ، دانشگاه شهید بهشتی، تهران، ایران

چکیده

توصیف رفتار واقعی سازه‌ ها به طور اجتناب ناپذیری وابسته به منابع عدم قطعیت یا پارامترهای تصادفی موثر در آن می‌باشد. این عدم قطعیت‌ها ممکن است به صورت تغییرات و پراکندگی در نیروهای خارجی، شرایط محیطی، شرایط مرزی، پارامترهای هندسی یا مشخصات مصالح ظاهر شوند. یکی از عوامل تاثیرگذار در تحلیل رفتار سازه‌های بتنی، در نظر گرفتن دقیق اثر ترک خوردگی‌ در المان‌های سازه‌ای است که در محاسبه دقیق‌تر دوره تناوب سازه، جابجایی طبقات و سایر پارامترهای پاسخ تاثیر مستقیم دارد. در آیین نامه‌های مختلف طراحی سازه های بتنی اثر ترک خوردگی به صورت ضرایب میانگین و ثابت برای هر المان سازه‌ای در نظر گرفته می‌شود، در حالی که به طور وضوح شرایط اجزای مختلف بر اساس وضعیت بارگذاری و مشخصات متفاوت است. در این مقاله با استفاده از روش شبیه سازی مونت کارلو، قابلیت اطمینان ضرایب ترک خوردگی تیر و ستون های بتنی در آیین نامه ACI تحت توزیع تصادفی بار زنده در طبقات مورد بررسی قرار گرفته است. بدین ترتیب با استفاده از روش مونت کارلو، با احتساب 1000 حلقه مدلسازی و محاسبه دقیق ترک خوردگی‌های تیر و ستون در هر مدل، قابلیت اطمینان ضرایب ترک خوردگی بدست آمده است. نتایج نشان می‌دهد که شاخص قابلیت اطمینان این ضرایب بسیار کم می‌باشد. همچنین از دیگر نتایج این مدلسازی و اعمال ضرایب دقیق ترک خوردگی، کاهش 40 الی 55 درصدی در جابجایی طبقات، کاهش 20 الی 30 درصدی دوره تناوب در مد اول و دوم و افزایش عکس العمل نیروهای المان ها بویژه نیروی محوری و پیچشی می‌باشد.

کلیدواژه‌ها

عنوان مقاله [English]

Investigating the effect of probabilistic distribution of crack at the limit state on the seismic reliability of concrete buildings

نویسندگان [English]

  • Mohammad Safi 1
  • Majid Koolivand 2
  • Mahsa Rasouli 2
  • Hesam Ketabdari 2
1 Assistant Professor, Department of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran.
2 Ph.D. Student, Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
چکیده [English]

Description of the real behavior of the structures depends on the sources of uncertainty or effective random parameters of the inputs and structural characteristics. These uncertainties may appear as changes and dispersal in external forces and environmental conditions, boundary conditions, geometric parameters or specification of the materials. One of the effective factors in the analysis of concrete structures is consideration of the effect of cracking on the structural elements, which directly affects the calculation of the natural periods, the story displacement and other response parameters. In different codes for design of concrete structures, cracking effect is considered as a mean and constant coefficient for each element, while clearly the condition of various components will be different based on loading situation and specifications. In this paper, reliability of stiffness reduction coefficients of the beams and columns due to cracking of concrete in the ACI code is investigated under random distribution of floor live loads using Monte Carlo simulation method. By considering 1000 modelling loops, calculating accurate crack coefficients of beams and columns and applying them in each model, the reliability of cracking coefficients has been obtained. The results show that the reliability index of these coefficients is very low. Also, other results of this modeling and applying accurate cracking coefficients, show that the story displacements and time period of first and second modes decrease about 40-55% and 20-30%, respectively and the reaction forces of the elements, especially the axial forces and torsional moments increase about 20-30%.

کلیدواژه‌ها [English]

  • Cracking coefficients
  • Concrete Elements
  • Mont Carlo Simulation
  • Design Codes
  • Reliability

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