A Simplified Design Procedure to Improve the Seismic Performance of RC Framed Buildings with Hysteretic Damped Braces

Abstract

The study presents an effective and easy to use design procedure for the seismic upgrade of frame structures equipped with hysteretic dampers, in order to attain, for a specific level of seismic intensity, a designated performance level. The frame-dampers structural system is idealized as an equivalent Single Degree of Freedom (SDOF) system, characterized through its secant stiffness and equivalent viscous damping. The global stiffness and strength of the equivalent SDOF system are distributed along the height of the frame according to a stiffness-proportionality criterion, which constrains the drifts of the braced frame to follow the first mode deformation of the main frame. To demonstrate the effectiveness of the design procedure, a case-study is chosen as paradigmatic of a category of existing buildings in Italy designed according to outdated codes. In order to assess the suitability of the design procedure, non-linear static analyses are performed on the upgraded building, showing a satisfactory agreement between the design target and numerical capacity curves. To have a deeper insight, also bidirectional non-linear dynamic analyses are performed in accordance with the provisions of the Eurocode 8.