Damage detection in a framed building structure

Interest in infrastructure health monitoring and damage detection has received a considerable amount of attention over the past two decades. Previous approaches to non-destructive evaluation of structures to assess their integrity typically involved some form of human interaction. Recent advances in smart materials and structures technology has resulted in a renewed interest in developing advanced self-diagnostic capability for assessing the state of a structure without any human interaction. The goal is to reduce human interaction while at the same time monitor the integrity of a structure. With this god in mind, many researchers have made significant strides in developing damage detection methods for civil structures based on traditional modal analysis techniques. These techniques are often well suited for structures which can be modeled by discrete lumped-parameter elements where the presence of damage leads to some low frequency change in the global behavior of the system. On the other hand small defects such as cracks are obscured by modal approaches since such phenomena are high frequency effects not easily discovered by examining changes in modal mass, stiffness or damping parameters. This is because at high frequency modal structural models are subject to uncertainty. This uncertainty can be reduced by increasing the spatial order of the discrete model, however, this increases the computational effort of modal-based damage detection schemes. On the other hand, wave propagation models of structures have higher spatial order model fidelity. Thus, they are better suited for detecting small defects since they are sensitive to changes in local mechanical impedance. This paper discusses the use of local and global wave propagation models to detect damage in a discrete model of a framed building structure, consisting of discrete structural elements. Simulated damage in the form of mass or stiffness loss is used to determine the effect on the resonant and incident wave response of the structure. Examination of the incident transfer function response of the structure reveals the loading path of the damaged element.