Evaluation of Seismic Damage of Multi-Storey RC Frames with Damage-Based Inelastic Spectra

In the context of performance-based design. structural damage as a comprehensive measure of the seismic demand against the available capacity may be used as an effective performance indicator Accurate methods of damage estimation usually require sophisticated dynamic response analysis and yet they do not necessarily yield the best results due to the great uncertainties involved in the seismic input. A simple and rational method based on well-constructed response spectra could be more desirable, especially in a design environment. In this paper, a methodology is developed to estimate the seismic damage of multi-storey reinforced concrete (RC) frames in terms of both the overall (global) damage and the damage distribution. The multi-storey frame is first transformed into an equivalent SDOF system. so that the damage in the equivalent SDOF system can be found from the damage-based inelastic spectra for a specified seismic intensity. Numerical investigation on a series of generic frames under a selection of real ground motions indicates that the SDOF damage and the overall damage of the actual frame correlates in a consistent manner, thus the conversion from the established SDOF damage back to the overall frame damage is rather straightforward. Two alternative methods are proposed for the prediction of the distribution of damage along the frame height, one using the modal pushover analysis, and the other based on the structural characterization using a storey capacity factor.