بررسی و تحلیل اثرات اصطکاک وابسته به سرعت در سازه مجهز به میراگر اصطکاکی تحت تحریک زلزله

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری سازه، گروه عمران، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران

2 استادیار،گروه مهندسی عمران، واحد علوم و تحقیقات، دانشگاه آزاداسلامی،تهران،ایران

3 گروه سازه و زلزله ، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی ، تهران ،ایران

چکیده

در این مطالعه سازه‌های مجهز به میراگر اصطکاکی، تحت اثر زلزله‌های حوزه دور و نزدیک مورد بررسی قرار می‌گیرند. نحوه لغزش و ارتعاش آن‌ها که شامل تغییر مکان، سرعت و شتاب می‌باشد به روش تحلیل عددی محاسبه می‌گردد. و پاسخ سازه تحت اثر زلزله‌های دور و نزدیک گسل ازیک‌طرف و نیز در نظر گرفتن مدل اصطکاکی ساده کولمب و مدل کامل‌تر اصطکاک وابسته به سرعت (اصطکاک Stribeck) مورد مقایسه قرارگرفته است. با وجود اینکه احتمال وقوع زلزله دور از گسل در یک منطقه بسیار محتمل است ولی وقوع زمین‌لرزه‌های بزرگ در نزدیکی شهرهایی که در مجاورت گسل‌ها قرارگرفته‌اند غیرقابل‌انکار است و این زمین‌لرزه‌ها دارای ویژگی‌های خاصی هستند که آن‌ها را از زلزله‌های دور از گسل متمایز می‌سازد. برخی از این ویژگی‌ها به‌صورتی است که اگر در نظر گرفته نشوند، منجر به تخمین نیروی زلزله بسیار کم‌تر از حد واقعی در طراحی سازه‌ها می‌شود. ازجمله این ویژگی‌ها می‌توان به تغییر مکان ماندگار یا اثر fling step و وجود پالس سرعت در مؤلفه عمود بر گسل می‌باشد که در اثر پدیده جهت پذیری پیش رونده (forward directivity) رخ می‌دهد، اشاره کرد.

با توجه به رفتار غیرخطی استهلاک نیرو، برای انجام آنالیز دینامیکی غیرخطی از برنامه‌نویسی و همچنین برای تحلیل سازه مجهز به میراگر اصطکاکی، از نرم‌افزار Open Sees استفاده شده است. نتایج نشان می‌دهد ساده سازه‌های مدل اصطکاکی لغزشی ازیک‌طرف و عدم تمرکز روی زلزله‌های حوزه نزدیک از طرف دیگر، باعث خطا در تخمین جابجایی‌ها و مخصوصاً نیروهای اعضا می‌گردد که با در نظر گرفتن اصطکاک Stribeck مقادیر خطا کاهش و نتایج مورد انتظار بهبود می‌یابد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation and analysis of the effects of velocity-dependent friction on structures equipped with friction dampers under earthquakes

نویسندگان [English]

  • Valiollah Davari 1
  • mohammad Reza Mansoori 2
  • Masoud Nekooei 3
1 Ph.D. Student, Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 Assistant professor, Department of Civil Engineering, Science and Research Branch, Islamic Azad University Tehran, Iran
3 Earthquake and Structure Engineering Department, Science and Research Branch, Islamic Azad university, Tehran, Iran
چکیده [English]

In this study, structures equipped with friction dampers under the influence of far-field and near-field earthquakes are investigated. How they slide and vibrate, which includes displacement, velocity and acceleration, is calculated by numerical analysis. And the response of the structure under the effect of far-field and near-field earthquakes on the one hand and also considering the simple friction model of Columbus and the more complete model of velocity-dependent friction (Stribeck friction) is compared. Although the possibility of a far-field earthquake is very likely, but the occurrence of large earthquakes near cities that are near faults is undeniable, and these earthquakes have certain specifications that distinguish them from far-field earthquakes. Some of these specifications are such that if neglected, they will lead to underestimation of the seismic force in the design of structures. Examples of these specifications are fling step effect and the presence of velocity pulse in the component perpendicular to the fault that is caused as a result of the phenomenon of forward directivity.

Due to the nonlinear behavior of the damping force (FD), programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in Open Sees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis. The results show that simplifications of the sliding friction model, on the one hand, and lack of focus on near-field earthquakes, on the other hand, result in underestimation of displacements, especially in member forces. Considering Stribeck friction, error rate is reduced and results are improved.

کلیدواژه‌ها [English]

  • Velocity-dependent friction
  • Far-field and near-field earthquake
  • Stick-slip phenomena
  • Symmetric Ricker wavelet
  • Friction damper
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