Seismic performance assessment of elliptic braced frames incorporating XADAS dampers

The elliptic brace is a new lateral resistance system recently presented. This paper investigates the performance of a yielding damper named X-shaped added damping and stiffness (XADAS) on the elliptic braced frame. For this purpose, 12 XADAS dampers with different numbers of plates, dimensions, and thicknesses were utilized on three braced frames. Also, three sections, including BOX 60×4, BOX 80×6, and BOX 100×10, were considered for the braces. The models were subjected to a cyclic loading and a non-linear static analysis. Three parameters, dissipated energy, fracture tendency and response modification factor, were evaluated to compare the models. The numerical analysis illustrated that the frames without dampers dissipate more energy at the end of loading due to higher stiffness, but they also experience more failures. Therefore, the models were compared at an equal value of dissipated energy and fracture tendency for a correct comparison. In comparing the models with the same fracture tendency, it was observed that the frame with a damper can dissipate up to 93% more energy than the model without a damper. The models with 15 cm-high dampers have experienced less damage, and in the models equipped with 9 cm-high dampers, more damage has been transferred to the dampers. The results showed that the model braced by the BOX 80×6 and equipped with the damper that the number, height and thickness of plates are respectively equal to 6, 15cm and 8mm has the best performance regarding dissipated energy, fracture tendency and response modification factor.