عملکرد لرزه ای پیکربندی جدیدی از میراگر اصطکاکی دورانی در مهاربندهای ضربدری

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه محقق اردبیلی، اردبیل، ایران

چکیده

در این مقاله پیکربندی جدیدی برای میراگر اصطکاکی دورانی پیشنهاد شده و رفتار آن تحلیل گردیده است. این میراگر دارای ساختاری بسیار ساده تر از میراگر پال بوده و المان اصطکاکی شامل مفصل و بازوها بر خلاف میراگر موآلا که در زیر تیر قرار می‌گیرد، در مرکز قاب بوده و از طریق کشش و فشاری که از مهاربندها اعمال می‌شود، مفصل اصطکاکی تحت لنگر دورانی قرار می‌گیرد. پارامترهای طراحی این نوع میراگر که در این مطالعه نیز مورد بررسی قرار گرفته اند، لنگر آستانه لغزش در مرکز میراگر، طول بازوی افقی و طول بازوی قائم میراگر است. رابطه ای بین مقادیر بهینه سه پارامتر یاد شده بدست آمده و هم چنین روشی ساده و مبتنی بر تحلیل استاتیکی معادل برای طراحی این میراگر ارائه شده است که لنگر لغزش بهینه را به طور متغیر در طبقات توزیع می‌کند. تعبیه میراگرهای بهینه در طبقات قاب و بررسی شاخص عملکرد آنها، برتری این روش توزیع را نسبت به توزیع یکنواخت نشان می‌دهد. توزیع متغیر روشی ساده و بدون نیاز به تحلیلهای دینامیکی غیر خطی زیاد برای یافتن بهترین شاخص عملکرد است. این روش شاخص‌های عملکردی بهتر از شاخص‌های بدست آمده از توزیع یکنواخت ارائه می‌دهد. هم چنین در توزیع متغیر لنگر لغزش در طبقات، همه میراگرها بخصوص در طبقه بام به خوبی به لغزش می‌افتند. در مطالعات موردی میراگر پیشنهادی شاخص عملکرد لرزه ای سازه را تا 11% بهبود داده است که در صورت توزیع بهینه در طبقات تا 17% نیز افزایش می یابد. کارآیی این سیستم در سازه های مرتفع تر و تحت زلزله های شدیدتر بیشتر است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic Performance of a Novel Configuration of Rotational Friction Damper in X Bracings

نویسندگان [English]

  • A. Gholizad
  • M. Morawej Nekoo
Engineering Department, University of Mohaghegh Ardabili, Ardabil, Iran
چکیده [English]

Seismic performance of a cruciform rotational friction damper has been evaluated in this article. Horizontal and vertical arms’ length and sliding threshold moment are three adjusting parameters of this device which shall be optimized to assure the damper efficiency. It has been shown that the energy dissipation rate increases for shorter arms due to more relative rotation between frictional contacting surfaces. The best dimensions for friction device arms have been evaluated in this study. A simple method has also been suggested based on static analysis and aiming to find the optimum sliding threshold moment for friction damper implemented at different stories. Closed form solutions of kinetic and kinematic equations of the damper dynamic have been employed on this regard. Dissipaters’ seismic performance indexes have been evaluated through nonlinear dynamic analyses to validate the reliability of the proposed method. It has been shown that the variant values of sliding threshold moment for optimum FD at different stories improves the seismic performance index in comparison with the case of identical devices utilized on all stories. Implementation of identical friction device on all stories may cause inactiveness of the dissipaters on upper stories where the inter-story shear force is not high enough and it acts as ordinary X bracings. The proposed method provides a simple and efficient approach for FD optimum design on different stories of building without multitude of time consuming nonlinear dynamic analyses. According to the dynamic analyses results inconstant optimally designed FDs will be active on all stories while identical FDs may not be sliding at upper stories during the earthquake. Performance of optimally designed FDs has been evaluated for 4, 8 and 12 story buildings under low, medium and high intensity earthquakes. It has been concluded that the proposed dissipater is more effective for high rise buildings and its efficiency increases for severe earthquakes. Although FD utilization on X-braces increases the inter-story drifts; base shear and residual energy considerably decrease. At last it results in 5%-20% improvement in seismic performance index. 3%-6% more reduction in SPI can be achieved using different sliding threshold moments for dampers on each story.

کلیدواژه‌ها [English]

  • Rotational Friction Damper
  • seismic performance
  • Threshold Sliding Moment
  • Optimum Configuration
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