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Numerical modeling of steel-framed floors for energy harvesting applications : modeling protocol, verification, parametric study, and optimization of a system : a report submitted to the faculty of the Milwaukee School of Engineering in partial fulfillment of the requirements for the degree of Master of Science in Structural Engineering / by Aaron M. Huberty.

by Huberty, Aaron M., author., Milwaukee School of Engineering

Steel framing (Building)

Microelectricalmechanical systems

Energy harvesting

94 leaves : illustrations, some of which are in color ; 29 cm.

Introduction and literature review -- Construction of the numerical model -- Model validation and parametric studies -- Conclusions -- Appendix A: time history study results.

Lightweight steel-framed floors have been known to be susceptible to vibrations. Pedestrian traffic on these floors is capable of exciting several vibration modes. Structural engineers typically design to minimize these vibrations. However, some of these modes may be targeted to harvest low-demand energy with the use of a Micro-Electrical Mechanical System (MEMS). Modal analysis is a useful tool for determining the resonant frequencies of a floor system. Recent advances in MEMS technology and vibration analysis, as well as increased demand for sustainable energy sources, have prompted the creation of intermediate scale energy harvesters with the ability to capture vibrations with low frequency content. In order to optimize the coupled system of steel-framed floor and harvester, an accurate numerical model must be created and evaluated. A numerical model of an existing experimental floor is presented. The existing floor system was selected for study because the modal frequencies, damping ratios, and mode shapes had already been determined, allowing for easy comparison to the numerical model. A parametric study was performed on the numerical model to optimize design of the coupled floor-harvester system. The study was done by varying the mass and stiffness of a harvester in the numerical model and measuring the resulting displacements, accelerations, and response frequencies. The process of the model's creation, validation studies, and results are discussed. The numerical model was able to accurately portray the dynamic behavior of the experimental model as well as optimize basic parameters for the energy harvesters and show locations that would result in the highest performance from the harvesters. The model was able to replicate the dynamic behaviors of the floor accurately for the first 5 modes of vibration, with the largest margin of error being 25.6% (in the 3rd mode), and the smallest margin of error being 0.85% (in the 1st mode). Additionally, the model was able to show that the areas of the floor with the greatest acceleration occurred at the regions experiencing greatest displacement during the 3rd, 4th, and 5th modes. Finally, the model was able to show that during a 0 - 30 Hz slow sweep, the coupled harvester experienced accelerations greater than 0.1g during 31.74% of vibrations.

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