A story damage index of seismically-excited buildings based on modal frequency and mode shape

In this paper, a story damage index (SDI) is developed and expressed as a simple formula based on modal frequency and mode shape obtained from real earthquake records. It is useful because only one set of modal parameters is required for the calculation of the SDI to show the degree of damage of the storey in question. According to numerical simulation results, it is shown that the proposed SDI has both high accuracy and high reliability. The approximate SDI, named ASDI, is more convenient and can be applied without the floor mass information. It is verified by some numerical simulations and the experimental data analysis for a benchmark (IASC-ASCE Phase II) model. This ASDI is also applied to the damage assessment of a 7-storey reinforced concrete hotel building in Van Nuys, California, which experienced severe structural damage during the 1994 Northridge earthquake. With both its fundamental frequency and mode shape identified by the SRIM (System Realization using Information Matrix) identification technique, it is shown that the ASDI agrees fairly well with the results of the visual inspection, and is valuable in practical application.