A simplified design procedure for seismic upgrade of frame structures equipped with hysteretic dampers

This paper presents a simple and affordable design procedure for the seismic upgrade of frame structures equipped with hysteretic dampers. The proposed framework is aimed at leading the designer to proportion the damper device(s)) in order to achieve a desired structural performance level. According to the method, the structural system composed by frame and dampers is replaced by an equivalent Single Degree of Freedom (SDOF) system, characterized through its secant stiffness and equivalent viscous damping, both defined in relation to a “performance point” which is assigned on the basis of the allowable damage of the frame and on the first mode deformation of the main structure. The global stiffness and strength of the equivalent SDOF system are then distributed along the height of the frame according to a stiffness-proportionality criterion, and the properties of the damper units are calculated depending on the chosen layout. Two case-studies relevant to as many reinforced concrete frames are provided to demonstrate the effectiveness of the suggested procedure, obtaining a satisfactory agreement between the design target and numerical capacity curves. Non-linear dynamic analyses are further performed to assess the reliability of the methodology.