In recent years, much research and development has been carried out on the use of vibration characteristics to detect structural damage in various types of structures. Being a type of the widely developed methods, the vibrations based damage detection methods, in particular modal based methods, are found to be promising in assessing the “health” condition of a structure in terms of locating and quantifying damage. However, despite of advances in vibration based damage detection methods of numerical simulations and some laboratory experimental implementations, very limited progress has been reported in field applications. The main obstacles in field applications are associated with the uncertainties, such as measurement noise, processing errors and error due to limited measurement points. In addition, the complexity of civil structures and/or materials further undermines the effectiveness and reliability of developed damage detection methods. This is evident by the fact that much less research and development has been reported for timber or reinforced concrete structures in terms of damage detection. It is therefore necessary to investigate effects of measurement noise, processing errors and errors due to limited measurement points on damage detection and develop a new robust and reliable method to locate and quantify damage in reinforced concrete structures.