تاثير حلقه‌ي فولادي در قاب‌هاي مهاربندي‌شده‌ي هم‌مركز تحت زلزله‌هاي مصنوعي به روش موجك

Effect of Steel Ring in Concentrically Braces Frame with Wavelet Based Artificial Earthquake

قاب‌هاي مهاربندي‌شده‌ي هم‌مركز به عنوان يكي ازسيستم‌هاي مقاوم در برابر بار جانبي، ضمن داشتن سختي بالا، مسايل اقتصادي و سهولت اجرا نسبت به قاب‌هاي خمشي شكل‌پذيري كمتري دارند، در دو دهه‌ي اخير، پژوهش‌هاي متعددي در زمينه‌ي افزايش شكل‌پذيري اين سيستم بر روي المان‌هاي جاذب انرژي در محل اتصال بادبند به صفحه‌ي گوشه انجام شده است. حلقه‌ي فولادي يكي از انواع المان‌هاي جاذب انرژي است، كه به صورت تحليلي و آزمايشگاهي مورد بررسي قرار گرفته است. حلقه‌ي فولادي در هنگام وقوع زلزله از ورود ساير اعضا به ناحيه‌ي غيرخطي و كمانش در مهاربند جلوگيري مي‌كند و يا آن را به تعويق مي‌اندازد، در اين نوشتار، ضمن مدل‌سازي و انجام آناليز غيرخطي قاب‌هاي خمشي مهاربندي‌شده‌ي هم‌محور، تاثير حلقه‌ي فولادي يك بار تحت زلزله‌هاي موجود و بار ديگر تحت زلزله‌هاي مصنوعي توليدشده به روش موجك مورد بررسي قرار گرفته است. نتايج نشان مي‌دهد حلقه‌ي فولادي ضمن كاهش برش پايه، عملكرد مطلوبي در استهلاك انرژي خواهد داشت.

Concentrically braced frames are a lateral resistant system in steel structures that is used more than any other structural system, because of ease of implementation, high stiffness and economic viability. However, they have less ductility compared to moment frames. In the past two decades, extensive research has been undertaken to increase their ductility. One of these methods is using energy dissipation fuses. There are several types of these elements designed for flexure, shear and torsion. A steel ring is a new flexural fuse that can be installed in concentric braced frames. The steel ring has been studied experimentally, showing a high energy absorption capability and high ductility. Since the maximum load bearing capacity of the brace elements is the same as the ring, they can be designed in such a way to prevent braces from buckling. In this paper, the effect of the steel ring on the response of the system is described using modeling and the nonlinear analysis of braced frames; once under an existing earthquake and once again on a synthetic earthquake generated based on the wavelet method. In this order, two cases including, ten and fifteen–story moment braced frames with and without steel rings were selected. The results in the orginal records show that by application of the steel ring, the relative displacement of the frame increases in the stories, especially the middle ones. Also, the base shear of the frame decreased. The percentages of decrease in the base shear for 10 and 15 story frames are 31% and 21%, respectively. The results of the base shear of two frames in the artificial records by application of the steel ring, showed the same tendency as in the initial records. However, the percentages of decrease in the base shear of the artificial earthquakes obtained for 10 and 15 story frames are 17% and 28%, respectively. In fact, the steel ring controlled the earthquake by absorbtion of energy, reduction of base shear and an increase in relative displacement.