dc.description.abstract | Structural health monitoring (SHM) is the process of evaluating a structure with the
use of sensors to provide an accurate representation of its current condition. Damage is
identified, located, and quantified in order better understand the deterioration of the structure
and allow for informed decision-making. Vibration-based damage detection uses
accelerometers to measure the response of the structure due to ambient or applied loads and
calculates modal properties based on the measured response. These modal properties (natural
frequency, mode shape, modal damping) are functions of properties of the structure (mass,
stiffness); thus, a change in modal properties can be an indicator of damage. Only a portion
of each structure was investigated, using a process called substructuring. Substructuring is
the process of studying only a small section of the structure and identifying local behavior.
Using measurements from the boundaries of the substructure, a virtual force was calculated
to restrain the boundary to zero response. The response of the isolated substructure was
calculated by superimposing the (measured) global response with that from the applied
virtual supports. The natural frequencies of the isolated substructure were then calculated and
compared to the expected (undamaged) frequencies. A significant difference between the two
indicated damage within the substructure. The substructural health monitoring technique is
validated using a spring-mass and modeled beam. Local frequencies are shown to be
sensitive to local damage, insensitive to damage outside of the substructure, and change with
the severity of damage. | en_US |