Application of Lower Grade Steel on Dynamic Behavior of X-Braces in Shear, Part 2: Advanced Nonlinear Static and Incremental Dynamic (IDA) Analyses

In first part of this paper, the theory of design of X-braces using different steel grades introduced and its effects on different frames verified using nonlinear static analyses. It was found hat using lower grade steel in X-braces increases the stiffness, energy absorption capacity, dampingand ductility of system and decreases its lateral drift. In order to completely investigate behavior of steel structures with X-bracing system in design with different steel grades and consider their dynamic behavior, the frames with different stories studied using advanced nonlinear static and Incremental Dynamic Analyses (IDA). The results presented as comparative diagrams and tables. The near and far field earthquakes used for dynamic analyse sand their seismic performance studied. Therefore, this research can lead to better investigation of seismic behavior of X-braced systems in design with different steel grades. The proposed theory along with analyses show that building codes and steel seismic design specifications can consider the effects of steel grades in seismic parameters definition of structures.The comparative diagrams and tables show that the seismic behavior of X-braces designed with lower grade steel improves considerably. In addition, the response of structures under near field earthquakes is bigger than related parameters under far field earthquakes.