Seismic Retrofitting of Eccentrically Braced Frames by Rocking Walls and Viscous Dampers

Abstract

A design procedure for seismic retrofitting of eccentrically braced frames (EBFs) by rocking walls and viscous dampers is proposed. The design procedure is founded on the displacement-based approach. The top displacement capacity of the building is evaluated based on the displacement ductility capacity of links and on a rigid lateral deformed configuration of the structure promoted by the rocking walls. The equivalent viscous damping ratio capacity of the EBFs with rocking walls is calculated by semi-empirical relationships specifically calibrated for EBFs with links characterized by mechanical length lower than 2.0. Additional damping is provided by linear viscous dampers. The design internal forces of the rocking walls are evaluated based on the seismic effects of more than one mode of vibration. The effectiveness of the design procedure is verified by means of a case study.