SEISMIC DESIGN OF CONCRETE FRAMES UPGRADED BY SHEAR-BENDING COMBINED METALLIC DAMPERS BASED ON CAPACITY CURVE METHOD

With the increasing seismic performance requirements of structures in recent years, existing concrete frames could not meet the requirements of multi seismic performance objectives. Adding metallic damper in existing concrete frames could significantly improve their seismic performance to meet current performance objectives. However, there is still lack of seismic design method for concrete frames upgraded by metallic damper. This paper proposed a seismic design method for concrete frames upgraded by metallic damper based on the capacity curve method, in which the shear-bending combined damper with multi-stage yielding feature was incorporated to achieve various performance objectives under different earthquake intensities. The equivalent bilinear capacity of concrete frames was obtained based on pushover results. The intersection points between the capacity curve of upgraded structure and demand spectrum could be determined after setting story drift performance objectives under frequently occurred, design-based and maximum considered earthquakes. The equivalent damping of the whole structure was calculated considering the additional viscous damping after the yielding of metallic damper. The yielding strength of shear and bending plates of metallic damper could be calculated through the performance intersection points. Following the design process, shear-bending combined dampers were designed to upgrade the 4-story, 6-story and 9-story concrete frames. The analytical modelling of the structures was established using OpenSees software and verified against the experimental results. It showed that the upgraded structures could meet the desired performance objectives through time-history analyses, indicating the efficiency and reliability of the design method. The research results in this paper provided guidelines on seismic design of metallic damper to upgrade concrete frames.