كنترل پيچش ساختمان‌هاي يك‌طبقه‌ي نامتقارن جرمي توسط ميراگرهاي اصطكاكي

TORSIONAL CONTROL OF MASS ECCENTRIC ONE STORY BUILDINGS BY FRICTION DAMPERS

مطالعات گذشته حاكي از عملكرد مثبت ميراگرهاي اصطكاكي در كنترل پيچش سازه‌هاي نامتقارن است. هدف از اين مطالعه تعيين پارامترهاي موثر و مقدار آن‌ها در كنترل پيچش سازه‌ي نامتقارن جرمي توسط ميراگرهاي اصطكاكي است. براي اين منظور ساختمان‌هاي فولادي براساس يك مدل متقارن پايه و به‌ازاي خروج از مركزيت‌هاي مختلف جرمي، توزيع‌هاي مختلف ميراگر و مشخصات ميراگر اصطكاكي و مهاربندهاي متصل به ميراگر اصطكاكي توسط نرم‌افزار OpenSees مدل شده و مورد تحليل قرار گرفته‌اند. پاسخ‌هاي حاصل از ساختمان مجهز به ميراگر براي حالات مختلف توزيع مقايسه شده‌اند و پارامترهاي موثر و مقدار آن‌ها در رفتار نظير حالات بهينه‌ي وضعيت قرارگيري ميراگرها، بار لغزشي بهينه‌ي ميراگر اصطكاكي، مهاربند متصل به ميراگر اصطكاكي مورد مطالعه قرار گرفته‌ است. در نهايت مي‌توان نتيجه گرفت چنانچه پارامترهاي ذكر‌شده در حالت بهينه در سازه‌ي نامتقارن مورد استفاده قرار گيرد، ميراگرهاي اصطكاكي توانايي كنترل پيچش ضعيف و قوي سازه‌هاي نامتقارن را دارند.

Torsion has been recognized as a main failure mode in past earthquakes. One efficient method of reducing earthquake effects is the application of energy dissipation devices, such as dampers. Friction dampers are among the simplest energy dissipation devices. Although there is much research on the use of friction dampers in symmetric buildings, there are fewer studies reported on asymmetric buildings. Results of those limited past studies show that the performance of friction dampers in the control of torsion in asymmetric structures is considerable. The aim of this investigation is to determine effective parameters and their range of effective values for torsional control of asymmetric buildings by friction dampers. For this purpose, steel buildings have been modeled and analyzed by OpenSees. The asymmetric buildings in this study are assumed to be classified as mass eccentric buildings. These models are symmetric, with respect to stiffness and strength distribution, and their eccentricity is due to their asymmetric mass distribution. Different levels of mass eccentricity are considered in parametric studies. Damper placements are investigated to identify their optimum distribution in having the largest effect in reducing the adverse effect of torsion in asymmetric buildings. The characteristics of friction dampers are also changed to cover a wide range of realistic values. Also, considered in parametric studies, are the properties of braces, which are connected to the friction dampers. The effects of these parameters have been evaluated, not only in optimum placement, but, also, in the value of the slip load of friction dampers. The results show that the use of resulted optimum distribution and the recommended characteristics of friction dampers can control torsion in asymmetric buildings.