Evaluation of seismic behavior of reinforced concrete frames with buckling restrained braces (BRB) in zigzag configuration in high-risk seismic zone

In the event of earthquake, structures are impacted by severe seismic loads which results in entrance of some of their lateral load-resisting members to the nonlinear zone. In such case, main part of input energy will be dissipated through structural intrinsic damping and non-linear hysteretic mechanism. In more intense earthquakes, input energy increases and more energy will be lost due to creation of plastic deformations. Such deformations are resulted from creation of local plastic joints in some parts of structure which in turn causes more energy dissipation in the system. As a result, great amount of seismic input energy to the building will be dissipated, because of local damages in lateral load-resisting system. This way, structure will lose its efficiency and eventually collapses if necessary measures would not be taken. During recent years, innovative methods of increasing efficiency and safety of structures against natural hazards including earthquake have been researched and presented. In the research 10, 15, and 20-storey structures have been studied. They are 3D structures with 3 and 2 spans in x and y directions, respectively. It should be noted that, primary design has been prepared in E-Tabs; then, non-linear time history analysis has been performed via Perform 3D. In terms of stiffness and ductility also, adding zigzag BRB results in approximately 10% increase in stiffness; while, ductility does not drop much. Therefore, structures with diagonal BRB may be replaced with zigzag BRB structures with acceptable accuracy, provided that required stiffness is more than what is expected. In cases of structures with zigzag BRB, stiffness will be increased, and ductility reduction factor will be reduced. In other words, structure being rehabilitated via zigzag BRB has lower ductility and yield strength within elastic and plastic limits. Also, the results show that energy absorption level in much more in zigzag structures, comparing to those with moment frame.

Keywords:

Reinforced Concrete structure , Buckling-Restrained Brace (BRB) , Zigzag configuration , High-risk seismic zone