The research reported in this thesis is part of a project to develop a remote wireless sensing network for monitoring the health of highway bridges. Remote health monitoring that does not require direct human observation has many advantages in terms of cost and increased productivity. However, bridges that cannot be easily connected to the power grid require alternative means of acquiring power. This thesis describes the design of a wind energy harvester to power a particular component in the sensor network, the wireless router. The work discussed in this thesis provides a review of relevant literature and development of a detailed analytical modeling of wind turbine behavior. The analytical model provides key information on sizing generators and choosing appropriate wind turbine dimensions to provide the required amount of power. The analytical model also distinguishes the performance of vertical and horizontal axis wind turbines. The model is verified through design and testing of a first generation prototype and benchmarking of a commercially available turbine. Based on these results, the design of the next generation wind harvesting system is described. A new methodology to design non-destructive attachment systems is also discussed. / text

The work described in this thesis discusses the design of a solar energy harvesting system to support a structural health monitoring system. The objective was to design a photovoltaic system capable of powering a wireless gateway and cellular modem, a static DC 14W load, while meeting certain functional and energy requirements for deployment on a bridge. A literature review of the application, technologies, components, and latest innovations in solar energy technology was completed. A methodology for designing a system for attaching energy harvesting systems onto bridges while meeting design requirements is presented as a tool for engineers and students. The use of the tool was demonstrated through a study which revealed that the methodology aided in producing concepts that were higher in quality, quantity, and better met design requirements. A PV array performance model was used to determine the proper PV module size, battery bank size, panel orientation, the usefulness of a solar tracker and MPPT charge controller, and whether the use of two separate PV modules with independent geometric orientations provide better performance as compared to a single larger panel. It was found from the study that the optimal PV system design specifications were a 120W Polycrystalline PV panel, a 120 A-hr LiFePO4 battery bank, a 45 degree tilt and 0 degrees solar azimuth angle (south), and an MPPT controller. The results from the analytical model also showed that the maximum energy produced with two independent panels would be at a solar azimuth angle of 0 degrees (south) and tilt angles of 45 and 50 degrees respectively. However, these energy gains were insignificant compared to simply increasing the size of the PV module. This result was verified by physical experiments. The physical embodiment of the solar energy harvester with these characteristics, including the mount to the bridge and the panel, was conceptualized, refined, analyzed for structural integrity, and prototyped. / text

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17106号 / 工博第3617号 / 新制||工||1549(附属図書館) / 29836 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 白土 博通, 教授 河野 広隆 / 学位規則第4条第1項該当

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21080号 / 工博第4444号 / 新制||工||1691(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 KIM Chul-Woo, 教授 杉浦 邦征, 教授 八木 知己 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This dissertation studied the structural identification and damage detection of civil engineering structures. Several issues regarding structural health monitoring were addressed. The data-driven subspace identification algorithm was investigated for modal identification of bridges using output-only data. This algorithm was tested through a numerical truss bridge with abrupt damage as well as a real concrete highway bridge with actual measurements. Stabilization diagrams were used to analyze the identified results and determine the modal characteristics. The identification results showed that this identification method is quite effective and accurate. The influence of temperature fluctuation on the frequencies of a highway concrete bridge was investigated using ambient vibration data over a one-year period of a highway bridge under health monitoring. The data were fitted by nonlinear and linear regression models, which were then analyzed. The substructure identification by using an adaptive Kalman filter was investigated by applying numerical studies of a shear building, a frame structure, and a truss structure. The stiffness and damping were identified successfully from limited acceleration responses, while the abrupt damages were identified as well. Wavelet analysis was also proposed for damage detection of substructures, and was shown to be able to approximately locate such damages. Delamination detection of concrete slabs by modal identification from the output-only data was proposed and carried out through numerical studies and experimental modal testing. It was concluded that the changes in modal characteristics can indicate the presence and severity of delamination. Finite element models of concrete decks with different delamination sizes and locations were established and proven to be reasonable. Pounding identification can provide useful early warning information regarding the potential damage of structures. This thesis proposed to use wavelet scalograms of dynamic response to identify the occurrence of pounding. Its applications in a numerical example as well as shaking table tests of a bridge showed that the scalograms can detect the occurrence of pounding very well. These studies are very useful for vibration-based structural health monitoring.

Structural health monitoring systems provide a promising route to real-time data for analyzing the current state of large structures. In the wake of two high-profile bridge collapses due to an aging highway infrastructure, the interest in implementing such systems into fracture-critical and structurally deficient bridges is greater now than at any point in history. Traditionally, these technologies have not been cost-effective as bridges lack existing wiring architecture and the addition of this is cost prohibitive. Modern wireless sensor networks (WSN) now present a viable alternative to traditional networking; however, these systems must incorporate localized power sources capable of decade-long operation with minimal maintenance. To this end, this thesis explores the development of two energy harvesting systems capable of long-term bridge deployment with minimal maintenance. First, an electromagnetic, linear, vibrational energy harvester is explored that utilizes the excitations from passing traffic to induce motion in a translating permanent magnet mass. This motion is then converted to electrical energy using Faraday’s law of induction. This thesis presents a review of vibrational energy harvesting literature before detailing the process of designing, simulating, prototyping, and testing a selected design. Included is an analysis of the effects of frequency, excitation amplitude, load, and damping on the power production potential of the harvester. Second, a solar energy harvester using photovoltaic (PV) panels is explored for powering the critical gateway component of the WSN responsible for data aggregation. As solar energy harvesting is a more mature technology, this thesis focuses on the methodologies for properly sizing a solar harvesting system and experimentally validating the selected design. Fabrication of the prototype system was completed and field testing was performed in Austin, TX. The results validate the selected system’s ability to power the necessary 14 W DC load with a 0° panel azimuth angle (facing direct south) and 45° tilt. / text