Equivalent Viscous Damping for the Displacement-Based Seismic Assessment of Infilled RC Frames

According to the displacement-based approach, in the seismic assessment of existing buildings it is required the definition of the equivalent viscous damping of the structure under study. As the hysteretic damping represents a measure of the dissipative capacity of structures, it is expected that it is larger for RC frames with masonry infills than for bare frames. At the date, the assessment procedure proposed within the displacement-based approach concerns only bare frame. The objective of this study was to extend the procedure to infilled RC frames by defining a ductility-damping law valid for this kind of frames. In order to obtain the mentioned relationship, several nonlinear dynamic analyses were carried out by applying different ground motions to single storey-single bay infilled frames. The effectiveness of the proposed ductility-damping law was then verified by comparing the displacement demand calculated with the assessment procedure with that obtained from nonlinear dynamic analyses.