Local damage detection using incomplete modal data

This paper introduces a new method that can identify the location and estimate the severity of damage in a structure using limited modal data such as: (1) few of the lower natural frequencies and mode shapes, (2) limited measurements of degrees of freedom, and (3) spatially incomplete measurements of mode shapes. The method is based on the physical interpretation of modal flexibility and an assumption that a small damage event will have an insignificant effect on the internal force of a structure under certain loading conditions. The method is applicable to incomplete modal data measured from either a forced vibration test or an ambient vibration test. One of the attractive advantages of the method is the localization of some faults using mode shapes. The method is believed to be efficient in the following situations: (1) if an inspection of the entire structure is not necessary, and (2) if only local measurements of modal data are available. The effectiveness, feasibility, and practicability of the method are investigated through modal data extracted from vibrational measurements from the Swiss Z24 Bridge.