عملکرد سازه ی مجهز به جداساز لرزه یی طبقه و آلیاژهای حافظه دار شکلی با پایه ی آهنی

در سال‌های اخیر، در ساختمان‌های خاص به طراحی جداسازهای لرزه‌یی در طبقات بالاتر از پایه که جداساز طبقه نامیده می‌شود، بسیار توجه شده است. با وجود این، جداسازهای لرزه‌یی با محدودیت‌هایی، از قبیل: ناپایداری در تغییرشکل‌های بزرگ، جابه‌جایی پسماند و غیره پس از زلزله‌های شدید هستند. استفاده از آلیاژهای حافظه‌دار شکلی با توجه به خواص منحصر به فردی که دارند، به عنوان راه حلی مناسب برای غلبه بر این نواقص درنظر گرفته شده‌اند. هدف از پژوهش حاضر، بررسی اثر ترکیب آلیاژهای حافظه‌دار شکلی و جداسازها در سازه و تاثیر آن‌ها در کاهش پاسخ لرزه‌یی سازه بوده است. به همین منظور، سازه‌ی چندطبقه‌یفولادی همراه با ترکیب جداساز لرزه‌یی طبقه و آلیاژهای حافظه‌دار شکلی با پایه‌ی آهنی و با استفاده از نرم‌افزار o‌p‌e‌n‌s‌e‌e‌s مدل‌سازی و ارزیابی شده است. نتایج به‌دست آمده نشان داده است که استفاده از آلیاژهای مذکور در جداسازهای لرزه‌یی طبقه باعث کاهش جابه‌جایی در تراز جداساز می‌شود و می‌توان آن را به‌عنوان سامانه‌یی مطلوب در مهار سازه‌ها در نظر گرفت.

Performance of Floor Isolation equipped with Shape memory alloys

Today, there is an increasing interest in use of seismic isolation to protect the structures against earthquakes. The most common type of seismic isolation is called base isolation, in which the isolation layer is installed under foundations to separate the structures from the ground and reduce the earthquake forces. However, the use of this type of seismic isolation faces some difficulties such as construction in congested urban areas or construction of near sea structures. Furthermore, for seismic retrofitting of existing buildings, the installation of the isolation under foundations is difficult or even impossible; so, it needs to be located on the middle floors of the buildings. The method of isolation design is called floor or middle story isolation. Despite the advantages of seismic isolations, they have some limitations such as instability in large deformations, residual displacement, and the need for replacement after severe earthquakes. The use of Shape Memory Alloys (SMA) regarding their unique properties is considered as an appropriate solution to overcome the above problems. These smart materials show high strength and strain capacity, high recentering ability, and high resistance to corrosion and to fatigue. The purpose of this study is to investigate the effect of combination of middle story isolation utilized by Natural Rubber Bearing (NRB) and ironbased shape memory alloys in steel structures and to compare the performance of such structures with and without the presence of the shape memory alloy in the middlestory isolation system. Then, a threestory steel structure has been modeled and evaluated. For this purpose, a structure with floor isolation and ironbased shape memory alloy was modeled in OpenSees computer program. The structures were then subjected to seismic loading. The results were presented in the form of story drift, floor acceleration, floor shear forces, and base shear. The outcome of this research showed that the use of these alloys in the middlestory isolation reduced the overall base shear and floor shear forces. The overall story drift, floor acceleration and displacement are reduced; with the exception at the isolation level. Thus, utilizing the natural rubber bearing isolator along with the ironbased shape memory alloy can be considered as a desirable system for the seismic protective design of buildings.