"In recent years, significant research efforts have been dedicated to developing self-powered wireless sensors without the limit of battery lifetime, such that they can be used to continuously monitor critical limit states and detect structural potential failures for structural health monitoring (SHM). As one of the most promising techniques, vibration-based energy harvester using piezoelectric transducer has been extensively used, given the advantages in size limitation and flexibility of embedding beneath construction surfaces. However, the low frequency of civil infrastructures' fundamental vibration modes (< 5 Hz) severely impedes the application of the energy harvester, since piezoelectric transducer only exhibits optimal outputs under a narrow range of natural frequency inputs (50-300 Hz). Recently, a mechanism has been developed to harvest energy at very low frequencies (< 1 Hz) using mechanical energy concentrators and triggers. This technique is based on the snap-through between different buckling mode transitions of a bilaterally constrained beam subjected to quasi-static axial loads. Attaching piezoelectric transducer to the buckled beam, electrical power can be generated by converting the quasi-static excitations into localized dynamic motions. The proposed mechanism can be implemented as an indicator for critical limit states, given the electrical power indicates the corresponding strain/deformation that a structure undergoes. However, the efficiency of the mechanism significantly depends on the post-buckling behavior of the deflected beam element. Inadequate controlling over the system's mechanical response critically impedes the application of the mechanism. Therefore, it is of research and practice interests to effectively control the mechanical response such that to maximize the electrical power and control the electrical signal. This study presents a technique for energy harvesting and damage sensing under quasi-static excitations. In order to optimize the harvesting efficiency and sensing accuracy of the proposed technique, which cannot be achieved by using uniform cross-section beams, non-prismatic beams are theoretically and experimentally studied. The mechanical response of the structural instability-induced systems are efficiently predicted and controlled. In particular, a theoretical model is developed using small deformation assumptions. Non-uniform beams are investigated with respect to the effects of beam shape configuration and geometry property. Piezoelectric scavengers with different natural frequencies are then used to convert the high-rate motions of the deflected beams at buckling transitions into electrical power. In addition, a large deformation model is developed to capture the buckling snap-through of the bilaterally constrained systems under large deformation assumptions. The model investigates the static and dynamic instabilities of bilaterally constrained beams subjected to gradually increasing loads. The model takes into account the impact of constraints gap under different constraint scenarios."--Pages ii-iii.
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