Experimental and numerical evaluation of the fundamental period of undamaged and damaged RC buildings

This paper deals with the period evaluation of Reinforced Concrete (RC) framed buildings in elastic, yield and severely damaged states. Firstly, period-height relationships either reported in the literature, or obtained from both numerical simulations (eigenvalue analyses) and experimental measurements (ambient vibration analyses) have been examined and compared. Structural types representing low-rise, mid-rise and high-rise RC buildings without earthquake resistant design, widely present in the Italian and European built environment, have been studied. Results have shown high differences between numerical and experimental period values. Period elongation (stiffness degradation) during and after strong ground shaking has been also examined based on results from experimental in situ and laboratory tests performed on some RC framed building structures which suffered moderate-heavy damage. Some comments on the relationship between damage level and period elongation are reported.