پیشنهاد قطعه جاذب انرژی با عملکرد محوری برای بهبود رفتار لرزه ای سازه های مهاربندی شده با مهاربند قطری

تجربیات به دست آمده از عملکرد سازه های مهاربندی شده با مهاربندهای همگرا طی سالیان گذشته محققان را بر آن داشت تا با ایجاد تغییراتی در اعضای مهاربندی به بهبود رفتار لرزه ای آنها کمک نمایند؛ نصب و استفاده از اعضای جاذب انرژی یک از این راهکارها بوده است که با توجه به تاثیر قابل توجهی که در پاسخ لرزه ای سازه ها ایجاد نموده همواره مورد توجه محققین گرفته است. لکن با بررسی تاریخچه تحقیقات انجام شده و با توجه به انعطاف پذیری قابلیت طراحی میراگرها به نظر می رسد می توان به طرح های کارا تری نیز در این زمینه دست یافت. در این مقاله سعی شده است تا ضمن انجام تحلیل های حساسیت بر روی پارامترهای موثر هندسی میراگرهای تسلیمی فولادی با ورق های موازی، نوعی میراگر تسلیمی جدید با عملکرد دو مرحله ای سخت شونده طراحی و ارائه شود. در ادامه با مقایسه نتایج به دست آمده از تحلیل های تاریخچه زمانی غیرخطی بر روی قاب در نظر گرفته شده، میزان تاثیر این میراگر در بهبود رفتار لرزه ای قاب سه طبقه بررسی شده است. نتایج به دست آمده نشان داد تغییر برخی پارامترهای هندسی تاثیر زیادی در شکل پذیری، تحمل نیرو و میزان جذب انرژی میراگر دارد؛ در عوض تغییر برخی پارامترهای دیگر تاثیر چندانی بر روی مولفه های ذکر شده نخواهد داشت؛ همچنین مقایسه پاسخ های لرزه ای نشان داد، استفاده از میراگر پیشنهادی ضمن جلوگیری از کمانش مهاربندها در محدوده ی تغییر شکلی تعریف شده، می تواند کاهش قابل توجهی بر روی پاسخ های لرزه ای قاب مورد نظر داشته باشد.

proposing an energy absorber component with axial behavior to improve the seismic performance of diagonal braced structures

convergent bracing system has long been considered by structural designers. however, the performance of this system during an earthquake has disadvantages such as high base shear, high roof acceleration and low energy absorption due to buckling of the braces. thus, researchers have tried to improve the behavior of the structure by proposing the use of different dampers in the lateral bearing section like friction, yielding and viscos dampers and buckling restrained braces. meanwhile, yielding dampers as low-cost dampers with easy manufacturing technology compared to visco-elastic and non-buckling dampers and flexible designing have always attracted the attention of researchers, however, the proposed designs have generally a one-level behavior and the yielding members cause instability of the frame in the case of the failure. in this research, a new type of steel yielding damper with two-level performance has been introduced using sensitivity analyses, in which the flexural yield of the parallel trapezoidal plates has been used for the energy absorption process. also, to ensure the stability of the braced frame in severe earthquakes, a simple support system has been included in its design. the geometrical dimensions of the damper are designed so as it doesn’t have any confliction with the architectural limitations. the damper has two plates at the ends to make its installation as easy as possible. it also has a pyramidal core that can be adjusted for stiffness and functional levels based on the seismic requirements of the frame. to perform this research, while performing finite element modeling by the abaqus finite element software, a comparative nonlinear time history analyses on a three 3 story frame has been done by coding the opensees. the frames were subjected to scaled accelerometers from fema p-695 and the story drifts, story velocity, base shear and roof acceleration parameters were compared. the results indicated the appropriate and stable cyclic behavior of the multi-level pyramidal damper, also showed that some geometrical parameters like the distance of two support plates and the thickness of the trapezoidal plate have more effects on cyclic performance and ductility of the device while the others has less. also increasing the thickness of the trapezoidal plate causes the activation of the shearing yielding mood in it and movement limitations. although the angle of the fuse plate decreases, a more uniform distribution of flow occurs on the surface of it, but the length of the end of the plate will be limited, which due to the limitations of the width of the fuse to avoid interfering with the architecture of the structure, its design will face problems. according to the results, the damping factor of the device has been obtained in range of 0.17 to 0.28 in cyclic behavior. the comparison of the results of the time history analyses showed that using the damper can cause a significant reduction on the base shear and roof acceleration seismic response of the frame, although the story drift and velocity responses of the frame increases, but the story drift values remain in the permissible range of regulations.