رفتار بهبود‌يافته‌ي آزمايشگاهي و تحليلي ميراگر فلزي آكارديوني تحت تاثير افزايش لايه‌ها

Experimental and Analytical Behavior of Accordion Metallic Dampers by Increasing the Number of Layers

در اين مطالعه با هدف بهبود رفتار ميراگر فلزي آكارديوني به عنوان يكي از بارزترين ميراگرهاي فلزي جاري‌شونده در داخل كشور، تاثير افزايش تعداد لايه‌هاي جداره‌ي اين ميراگر مورد مطالعه‌ي تحليلي، آزمايشگاهي و پارامتريك قرار گرفته است. مطالعات آزمايشگاهي بر روي نمونه‌هاي تك ‌لايه و دو لايه انجام شده و مدل‌هاي تحليلي تك ‌لايه، دو لايه و سه لايه‌ي ميراگر توسعه يافته و با استفاده از نتايج مطالعات آزمايشگاهي مورد صحت‌سنجي قرار گرفته است. همچنين تاثير تغيير پارامترهاي مهم هندسي جداره‌ي ميراگر در رفتار استهلاكي آن بررسي و مدل ايده‌آل هندسي ارايه شده است. به‌علاوه مطالعه‌‌يي تحليلي به جهت شناسايي ميزان تاثير چند لايه‌شدن ميراگر در قابليت تحمل تعداد سيكل‌هاي بارگذاري انجام شده است. نتايج به‌دست‌آمده از مطالعات نشان مي‌دهد كه افزايش تعداد لايه‌هاي ميراگر به دليل ايجاد پايداري بيشتر رفتاري، اصلاح مودهاي كمانشي تغييرشكل و همچنين تاثيرات مطلوب اندركنش بين لايه‌ها، تاثير بسزايي در مشخصات رفتاري ميراگر و افزايش تعداد سيكل‌هاي بارگذاري قابل تحمل آن دارد.

Over the last three decades, structural control systems have developed into three categories: Passive, Active and Semi active. The hysteretic metallic damper is among one of the most popular supplemental energy dissipation devices, as a type of passive control system. The accordion metallic damper (AMD) was suggested to be the best hysteretic metallic damper because of its high capacity to absorb energy and its desirable behavior characteristics, including convenient fabrication and installation. The efficiency of AMD to control and mitigate the response of structures under seismic loading is established, both experimentally and analytically. In this research, for the purpose of improvement, the effect of increasing the number of accordion tube layers on the damping behavior of AMD is investigated using experimental, analytical and parametric studies. Experimental studies were conducted on single layer and two layer specimens under axial loading by a dynamic Roell-Amsler actuator. Analytical studies, based on the finite element method, and inelastic dynamic analysis have been carried out on a series of single and multi-layer AMD models, which have been verified by experimental results. Also, the effect of changing geometrical parameters on the damping behavior, by increasing the number of layers, was evaluated, and an ideal geometric model is made available. Finally, an analytical study has been performed to determine the effectiveness of a multilayer damper on the tolerability of low-cycle fatigue. The results show that increasing the number of layers has a great influence on the amount of dissipated energy, loading capacity and elastic stiffness, due to greater stable behavior. This includes improving the buckling mode, preventing destructive modes of buckling and interaction effects between the layers. Parametric study shows that the combination of geometric parameters, such as thickness of layer, radius of tube, length of tube and radius of corrugation, will provide ideal model geometry with optimal energy absorption. A fatigue study shows that increasing the number of layers has good effects on increasing the number of cycles tolerated, and reduces the damage damper coefficient by decreasing the stress focus on critical areas of the damper wall.