A new modal based damage detection approach utilising added mass

To reliably detect structural damage and estimate damage severity at its early stage poses a great challenge to engineering community. Despite a great deal of research and development in the areas of damage detection and health monitoring, there are very few successful applications in real life damage detection in engineering practices. One of the main obstacles for successful application of damage detection algorithms to real life civil infrastructure is the complex nature of structures and the uncertainties associated with modelling and measurement. This paper presents a new modal based damage detection approach aiming to provide an effective means to improve reliability and accuracy of damage detection. The proposed approach requires measurement data from two states of the structure, i.e. data from the structure "as-is" and data from the structure after adding a known mass. By means of experimental modal analysis (EMA), the modal parameters of the structure with and without added mass can be obtained. With modal parameters of the said two states and the known added mass, the proposed method will be able to produce the "in-service" system stiffness matrix. With the element connectivity being known a priori (or assumed reasonably), the "in-service" element stiffness can be obtained. Location of damage as well as damage severity of the structure will therefore be known. Experimental verification of the proposed method was carried out using a three storey shear building model. The experimental results show that the proposed damage detection method is superior in both damage localisation and damage severity estimation.