پاسخ لرزه‌اي و خرابي پيشرونده سازه‌هاي قاب خمشي فولادي نامنظم در پلان مجهز به ميراگرهاي تسليم شونده TADAS

Seismic Response, Progressive Collapse Capacity of Irregular Buildings equipped with TADAS Damper

پژوهش­هاي گوناگوني در زمينه خرابي پيشرونده ناشي از بارگذاري غيرعادي نظير انفجار صورت پذيرفته است و سيستم­هاي مقاوم متعددي در اين زمينه مورد ارزيابي قرار گرفته است. هدف اصلي اين پژوهش بررسي تاثير بكارگيري ميراگر تسليم شونده فلزي Triangular Added Damping an‎d Stiffness (TADAS) به منظور بالا بردن ظرفيت سازه­هاي نامنظم سه و نه طبقه نامنظم در برابر زلزله و خرابي پيشرونده خواهد بود. به اين منظور با توجه به نياز سازه از ميراگر فلزيTADAS به جهت بهبود عملكرد لرزه­اي آن بهره گرفته شده است. سپس به منظور ارزيابي عملكرد اين ميراگر در بهبود ظرفيت سازه در برابر خرابي پيشرونده، سناريوهاي مختلف بحراني جهت حذف ستون انتخاب و ظرفيت سازه با استفاده از آناليز تاريخچه زماني غيرخطي توسط نرم افزار SAP2000 مورد ارزيابي قرار گرفته است. به منظور ارزيابي غيرخطي سازه، رفتار غيرخطي تيرها با استفاده از مفصل پلاستيك و به منظور در نظر گرفتن اندركنش غيرخطي نيروي محوري و لنگر خمشي از مدل فايبر براي رفتار غيرخطي ستون­ها استفاده شده است. مدل­سازي ميراگرها نيز با استفاده از المان لينك در نرم افزار و تخصيص دادن مدل غيرخطي WEN به آن انجام پذيرفته است. به منظور ارزيابي عملكرد لرزه­اي سيستم ميراگر از تحريكات پالس­گونه بهره گرفته شده است. نتايج ارائه شده نشان دهنده موفقيت بالاي 40 درصدي در كاهش جابجايي نسبي ميان طبقه ­اي مي­باشد. افزايش حداقل 15 درصدي وحداكثر 100 درصدي ظرفيت سازه مجهز به ميراگر تسليم شونده در برابر خرابي پيشرونده از ديگر نتايج اين تحقيق مي‌باشد.

In recent years, the use of supplemental damping devices to increase the capacity of structures against progressive failure due to explosion has received less attention. The main purpose of this research is to investigate the effect of using Triangular yielding metal damper called TADAS. in order to increase the capacity of an irregular three and nine-story steel moment frame buildings against pulse like seismic excitations and progressive collapse effect. For this purpose, seismic performance level of this structure has been evaluated and rehabilitated by TADAS damper. The seismic performance level of damper-equipped building was evaluated by nonlinear static analysis (pushover) and also nonlinear time history analysis under various pulse-like ground motions. In order to assess the performance of TADAS damper under progressive collapse phenomenon, 12 critical columns considering side and corner locations proposed by GSA code were selected to remove. Then considering the seismic nonlinear response of these columns under selected ground motions, four critical scenarios were selected for each building. According to irregularity of the structural plan the capacity of the rehabilitated structure was evaluated using nonlinear time history analysis. To simulate the progressive collapse phenomenon at first the internal column forces are evaluated before it is removed. These forces are dynamically applied to the structure as a nodal point load in addition to existed dead and live loads in five seconds after removing the column. After completing the amount of loading they kept unchanged for two second and finally the nodal point loads would be removed over a fraction of second and therefor the dynamic sudden column removal was simulated. The nonlinear response of the irregular TADAS-equipped building was computed through the step by step numerical integration method known as the Newmark’s β-method integration procedure using SAP2000 software. A fiber element model was employed to take into account the non-linear behavior of columns while for beam elements it is used plastic hinge model considering ASCE41 code. The dampers are also modeled using the link element in the software and the nonlinear plastic Wen model is assigned to simulate the nonlinear behavior of this element . The presented results include comparison of roof displacement diagrams, inter story drift and center mass acceleration for the structure with and without dampers in different failure scenarios. The seismic results show the ability of TADAS damper to improve seismic performance of irregular building. This control system could reduce the inter story drift of buildings at least 40% while the center mass acceleration increase 5.0% While the hysteresis diagram of dampers indicates their ability to suppress the response of this structure. These results indicate the success of the damping system in the simultaneous control of acceleration and displacement and indicate another result of this study. On the other hands the progressive collapse analysis results show the ability of TADAS damper to improve the capacity of the structure against four types of progressive failure scenario especially in scenario 2. The results showed that the vertical displacement was reduced at least 15%.