مقاوم سازي بهينه‌ي قاب خمشي فولادي با استفاده از روش توزيع يكنواخت تغييرشكل‌ها

Optimum Seismic Rehabilitation of Steel Moment Frames using the Uniform Deformation Method

به‌كارگيري ميراگرهاي فلزي به عنوان يك سيستم مستهلك‌كننده‌ي انرژي، روشي قابل قبول براي كنترل خرابي سازه‌ها و بهبود عملكرد لرزه‌يي آنهاست. در اين نوشتار، با بهره‌گيري از روش توزيع يكنواخت تغييرشكل‌ها، الگوي بهينه‌ي توزيع ميراگرها جهت كاهش پاسخ لرزه‌يي قاب فولادي چند درجه‌ي آزادي ارايه شده است، به نحوي كه پيكره‌بندي نهايي ميراگرها در قاب، در حالي كه معيارهاي عملكردي را تامين مي‌كند، كمينه‌ي وزن لازم را نيز داشته باشد؛. در اين مطالعه نشان داده شده است كه عملكرد لرزه‌يي چنين سازه‌يي بهينه بوده است و در آن از بيشينه‌ي ظرفيت سازه استفاده مي‌شود. در اين پژوهش روش بهينه‌سازي ذكرشده، به منظور بهسازي بهينه در سيستم‌هاي قاب خمشي با رفتار غيرارتجاعي و داراي ضعف اوليه در طراحي استفاده شده است و درنهايت، پيكره‌بندي بهينه‌ي ميراگرها در ارتفاع ساختمان مشخص شده است.

The rehabilitation of existing buildings or design of new resistant buildings under earthquake conditions, presents an important problem in earthquake prone countries. Different techniques and methods are used to rehabilitate structures such as passive energy dissipating devices. These systems are used to upgrade the performance level of structures and prevent structural damage during earthquakes. One energy dissipating device considered a passive control system, is the metallic-yielding damper. This passive control system is used to upgrade the performance of structures, modifying the stiffness, strength and damping of structures, simultaneously. These metallic seismic energy absorbing devices endure a large deformation in their mild steel plates, thus, yielding a large volume of steel and so increasing structural damping, which can dissipate substantial energy during an earthquake. According to presented optimization methods, various inelastic moment-resisting steel frames with some flaws in the primary design phase were rehabilitated optimally. In this research, employing the Uniform Deformation theory, a new trend is presented in order to decrease the seismic response of multi-degree moment-resisting steel frames. In this method, the basic aim of optimization is determining the optimum outline of dampers throughout the height of a structure, in such a way that the structure reaches allowable performance at the lowest cost. For modeling metallic-yielding dampers, nonlinear springs with Elasto-Perfectly-Plastic material are inserted into the structure on shevron chevron braces. It was shown that the structure retrofitted by this method has optimum seismic performance and uses its maximum capacity, while the structure satisfies seismic provisions. The effect of various parameters, such as number of stories, asymmetry, earthquake intensity and frequency content, on the optimization process, is studied. It is concluded that the number of iterations, the optimum objective function and the precision of convergence are highly affected by the mentioned parameters. The optimum outline and mechanical properties of dampers are dependent on applied earthquake ground motion.