Non-Dimensional Parameters to Design Damper Systems in RC Existing Framed Buildings

The use of dissipative bracing systems by hysteretic dampers represents one of the most efficient innovative techniques for the seismic retrofitting of existing structures, especially for reinforced concrete (RC) frame buildings. Many studies on design approaches and case studies have been developed in recent decades and are still in progress; however, the importance of the relation between the properties of the existing structure and of the damper system has not been analyzed, and the influence of the type of arrangement inside or outside the structure, has not been pointed out. In this paper, an innovative dimensionless approach is proposed to describe the dynamic structural properties of the retrofitted structure introducing ratios between the properties of the existing structure and damper system. Therefore, indications to optimize the design of the passive energy dissipation (PED) system can be clearly established for each case. Furthermore, a generalization of the design approach considering different solutions with internal and external bracings is proposed. The application of the dimensionless parameters to the design of a dissipation system for a single-bay three-story RC frame building and points out that damping can be reduced by two times if the capacity of the existing structure is used, further reducing the base shear transmitted to foundation. This result is also obtained by mounting the PED system on an external structure. The effect of infill walls on the stiffness of the existing structure requires an increment of the stiffness of the PED system with double the stiffness of the devices further than the buckling-restrained braces (BRBs).