Evaluation of seismic performance of X bracing systems equipped with flexural yielding dampers

The X-bracing system is one of the lateral loads bearing system. In X-bracing system’s elements, axial plastic hinges (compressive or tensile) will be formed instead of flexural hinges which are not capable to absorb high energy. Seismic performance can be improved by replacing these plastic hinges with the bending plastic joints. In this study, a new kind of X-bracing named X-bracing equipped with flexural yielding damper is introduced in which the plastic axial hinges is substituted by flexural plastic hinges. In this kind of bracing the failure mechanisms focuses on flexural hinges. The objective of this study is to evaluate the seismic performance of this kind of bracing. For this purpose, several X-bracing frames with various stories was selected and designed based on Iranian building codes. The seismic performance of these frames (stiffness capacity, strength capacity, and ductility capacity) and force reduction factors were evaluated using static and time history nonlinear analysis. In dynamic time history analysis seven acceleration-time records was applied. The results show that the damper reduces stiffness and strength capacity inconsiderably, but increases the ductility capacity significantly. It also increases the force reduction factor of the frames significantly. The amount of force reduction factor for this system is the same as eccentrically braced frame one.