Application of Lower Grade Steel on Dynamic Behavior of X-Braces in ShearPart 1: Classical Theory of Braces in Shear

Using Lower Grade Steel (LGS) in design of buildings increases ductility and energy dissipation capacity along with load bearing capacity with decreased seismic demands. In addition, the performance of structures increases because of decreased target displacement. Nevertheless, the majority of seismic design codes follow an approach that is irrespective of steel grade. The procedures of structural design with different steel grades are typical independent of demand and capacity curves, as the related design codes have specified the seismic parameters based on the type of structural system and often recommend the same behavior factor and over-strength coefficient for steels of different grades. This comprehensive study includes two major parts. The first part includes design theory development of structures for X-Bracing system for different grades of steel and the classic formulas introduced to calculate main capacity and demand parameters. Then, the accuracy of proposed theory verified with nonlinear static analyses which leads to enough accuracy for buildings with shear behavior. Also, using LGS in seismic design of X-bracing buildings increases stability, ductility and energy dissipation capacity under severe earthquakes. In the second part, the comparative behavior of frames with different steel grades studied using advanced nonlinear static and Incremental dynamic analyses and the effect of height of the building emphasized.