توزيع بهينه‌ي ميراگرهاي مثلثي‌شكل افزاينده‌ي سختي و ميرايي جهت بهبود عملكرد لرزه‌يي قاب‌هاي خمشي

Optimum Distribution of TADAS Dampers for Improving the Seismic Performance of Moment Frames

در اين نوشتار دست‌يابي به توزيع بهينه‌ي سختي ميراگرهاي افزاينده‌ي سختي و ميرايي (TADAS)، جهت بهبود عملكرد يك قاب 3 طبقه با استفاده از الگوريتم‌هاي بهينه‌يابي ژنتيك و توده‌ي ذرات انجام شده است. همچنين با ايجاد تغييراتي در الگوريتم تغييرشكل يكنواخت، توزيع بهينه‌ي ميراگرها با استفاده از الگوريتم مذكور به‌دست‌آمده و نتايج آن با دو الگوريتم ديگر مقايسه شده است. معيار ارزيابي عملكرد سازه نسبت تقاضا به ظرفيت اعضاست، كه مطابق با آيين‌نامه‌ي 06-41ASCE محاسبه شده است. نتايج نشان مي‌دهد الگوريتم تغييرشكل يكنواخت با انجام تحليل‌هاي بسيار كمتري نسبت به دو الگوريتم ديگر به توزيع بهينه‌ي سختي ميراگرهاي TADAS در ارتفاع قاب دست پيدا مي‌كند و هر چه نسبت تقاضا به ظرفيت طبقه يكنواخت‌تر شود، طرح مناسب‌تري به‌ دست مي‌آيد.

Different passive dampers have been presented in order to improve structural performance, and various investigations have been undertaken to find their optimum distribution by different methods. In this paper, optimal distribution of TADAS dampers to improve the performance of a 3-story steel moment frame is investigated. This frame has the same loading condition, mass, geometry, and beam and column material, as the moment resisting frame of a 3-story SAC building located in Los Angeles. The design of the members of the frame does not satisfy ASCE41-06 criteria. A nonlinear static procedure, according to ASCE41-06 instruction, is used to analyze the frame under seismic load. Based on the concept of the uniform distribution of deformation (UDD) algorithm, in order to obtain optimal design, structural resistance elements should be transferred from strong to weak portions. In this study, a modified UDD algorithm is used to achieve optimal distribution of dampers. This algorithm acquires the optimal stiffness distribution of TADAS dampers, with respect to the demand to capacity ratio (DCR) of the stories. The DCR of each story is equal to the maximum DCR of elements in that story, which is calculated based on ASCE41-06 regulations. First, the proposed algorithm assigns minimum stiffness to all dampers, then, increases TADAS stiffness in stories that have DCR greater than the allowable value, and vice versa. This process continues until uniform distribution for the stories DCR is achieved. Genetic and PSO algorithms are types of heuristic algorithms. Optimal distribution of dampers using these algorithms is also obtained and their results compare with the UDD algorithm. Heuristic methods utilize a stochastic search to find optimum solution. First, they generate a population of solutions, then, find proper solutions, with regard to the objective function, and in the next steps, attempt to produce better population. Finally, they converge to the optimum design. The results show that the optimum stiffness distribution of TADAS dampers is obtained when the distribution of stories DCR becomes uniform. Also, the UDD alogorithm acquires optimum distribution of dampers in fewer numbers of analyses in comparison with heuristic methods, because this algorithm uses engineering intelligence instead of stochastic search to find an optimum solution.