Motion magnification for optical-based structural health monitoring

Applications of motion magnification has been seen as an effective way to extract pertinent structural health monitoring data without the use of instrumentation. In particular, phase-based motion magnification (PMM) has been adopted to amplify subtle motions that cannot be seen clearly without further processing. For large infrastructure, this tool can be helpful in identifying the dynamic range of motion and modal frequencies. The use of accelerometers poses a problem for structures that contain large geometry, due to the complexities that arise when attempting to setup a modal test. Optically, one can identify singular points or regions of interest that capture a large range of motion for a structure. These regions of interest ultimately provide the dynamic information that is needed to perform structural health monitoring (SHM) of a complex system. This paper aims to identify a shift in frequency and operational deflection shapes due to varying loading scenarios while using PMM. The ability to capture multiple points without being limited by a data acquisition system permits further analysis of structural health. For example, the ability to apply varying loading scenarios can provide warnings as to how a frequency shifts while sustaining a particular force. Due to the plethora of loading conditions, the variation in external loading makes SHM a more conclusive process. For instance, it was applied many different scenarios for loading conditions and damages to observe the shifts in the frequencies due to each factor. It was also done testing with different sensing techniques and with traditional sensing to verify the reliability of PMM. The tests were done in laboratory structures and in real structures to prove the applicability of PMM and to verify what information is needed to identify damage in the structure.