<p>Vehicles that run on compressed natural gas and hydrogen are currently being developed to reduce greenhouse gas emissions and smog. To meet the need for a safe, reliable fuel storage system, a low-cost, acoustic-ultrasonic system has been developed to detect damage in high-pressure storage cylinders made of Carbon Fiber Reinforced Polymers (CFRP). This structural health monitoring system could lead to lighter, lower cost cylinders, and improved safety in automotive applications that utilize hydrogen and natural gas.</p><p>Several Non-Deconstructive Evaluation (NDE) techniques were investigated in the course of this work, and low-cost piezo-film sensors were selected to monitor the cylinder. These sensors were integrated into the carbon fiber structure, resulting in a sensor network that can be used for real-time structural health monitoring of composite cylinders. The system was operated by exciting the piezo-film sensors with an impulse and then the corresponding structural response (or signature) was measured and analyzed. This was compared to a previously measured response and evaluated for changes which can indicate failures in the tank. The analysis reduces the changes in the structural response to a single damage coefficient, which can then be used for malfunction indication and decision making in an automotive on-board microprocessor control system.</p><p>The technology can be deployed at a reasonable cost, and has been designed to accurately detect damage with little or no maintenance required. Thirty cylinders were used in a test matrix to examine all possible failure mechanisms of the tanks, including: fatigue, cuts and gouges, impact and delaminations, stress rupture, heat damage, and combinations of these damage mechanisms. The damage detection system was capable of detecting damage long before a critical condition arose for all cases. However, further development and testing into larger cylinder designs and testing is still required to develop a final commercial product.

Structural Health Monitoring (SHM) comprises a wide range of techniques for the condition and damage assessment of an existing structure. Vibration-based damage detection (VBDD) techniques, a class of SHM methods, use changes in the dynamic properties (i.e., natural frequencies, mode shapes and damping characteristics) of structures to detect deterioration or damage. The application of VBDD methods to simple structures in a well-controlled laboratory environment has gained some successful results. However, the practical field application of VBDD still faces significant challenges since vibration measurement is subject to the influences of high levels of uncertainty in environmental, structural and loading conditions. In this thesis, the influence of temperature variations on the application of VBDD methods to an in-service complex structure was experimentally and numerically studied. The structure studied was the Attridge Drive overpass in Saskatoon, Saskatchewan.<p> The main objective of this research was to assess the influence of temperature variation on the dynamic properties (natural frequencies and mode shapes) of the overpass, and on the ability of VBDD methods to detect and locate damage. Field dynamic measurements were made on the bridge on numerous occasions under a wide variety of ambient temperatures, using high sensitivity accelerometers and a temperature sensor. Dynamic excitation was provided solely by ambient traffic loading.<p> Finite element models of the overpass were also created and manually calibrated to measured field data. The models were used to simulate the dynamic behaviour of the bridge at a variety of temperatures and under various states of small-scale damage. Numerical analysis was conducted to study the effect of ambient temperature on structures dynamic characteristics and to differentiate the patterns of mode shape changes caused by damage and ambient temperature. It was concluded that the change of ambient temperature mainly affects the elastic modulus of the construction materials and therefore stiffness of the entire bridge. As a result, the eigenfrequencies and mode shapes of the structure are influenced.<p> The dynamic properties extracted from measured experiment data showed an approximately bilinear relationship between the three first natural frequencies and the ambient temperature. The natural frequencies for all three modes increased when the temperature fell.<p> It was also found that, conceptually, it is possible to distinguish the patterns of mode shape changes caused by small-scale damage from those due to thermal effects, but only if a sufficient number of sensors are used to measure the mode shapes; in addition, those sensors must be located close to the damage location.

<p>Vehicles that run on compressed natural gas and hydrogen are currently being developed to reduce greenhouse gas emissions and smog. To meet the need for a safe, reliable fuel storage system, a low-cost, acoustic-ultrasonic system has been developed to detect damage in high-pressure storage cylinders made of Carbon Fiber Reinforced Polymers (CFRP). This structural health monitoring system could lead to lighter, lower cost cylinders, and improved safety in automotive applications that utilize hydrogen and natural gas.</p><p>Several Non-Deconstructive Evaluation (NDE) techniques were investigated in the course of this work, and low-cost piezo-film sensors were selected to monitor the cylinder. These sensors were integrated into the carbon fiber structure, resulting in a sensor network that can be used for real-time structural health monitoring of composite cylinders. The system was operated by exciting the piezo-film sensors with an impulse and then the corresponding structural response (or signature) was measured and analyzed. This was compared to a previously measured response and evaluated for changes which can indicate failures in the tank. The analysis reduces the changes in the structural response to a single damage coefficient, which can then be used for malfunction indication and decision making in an automotive on-board microprocessor control system.</p><p>The technology can be deployed at a reasonable cost, and has been designed to accurately detect damage with little or no maintenance required. Thirty cylinders were used in a test matrix to examine all possible failure mechanisms of the tanks, including: fatigue, cuts and gouges, impact and delaminations, stress rupture, heat damage, and combinations of these damage mechanisms. The damage detection system was capable of detecting damage long before a critical condition arose for all cases. However, further development and testing into larger cylinder designs and testing is still required to develop a final commercial product.

Structural Health Monitoring (SHM) comprises a wide range of techniques for the condition and damage assessment of an existing structure. Vibration-based damage detection (VBDD) techniques, a class of SHM methods, use changes in the dynamic properties (i.e., natural frequencies, mode shapes and damping characteristics) of structures to detect deterioration or damage. The application of VBDD methods to simple structures in a well-controlled laboratory environment has gained some successful results. However, the practical field application of VBDD still faces significant challenges since vibration measurement is subject to the influences of high levels of uncertainty in environmental, structural and loading conditions. In this thesis, the influence of temperature variations on the application of VBDD methods to an in-service complex structure was experimentally and numerically studied. The structure studied was the Attridge Drive overpass in Saskatoon, Saskatchewan.<p> The main objective of this research was to assess the influence of temperature variation on the dynamic properties (natural frequencies and mode shapes) of the overpass, and on the ability of VBDD methods to detect and locate damage. Field dynamic measurements were made on the bridge on numerous occasions under a wide variety of ambient temperatures, using high sensitivity accelerometers and a temperature sensor. Dynamic excitation was provided solely by ambient traffic loading.<p> Finite element models of the overpass were also created and manually calibrated to measured field data. The models were used to simulate the dynamic behaviour of the bridge at a variety of temperatures and under various states of small-scale damage. Numerical analysis was conducted to study the effect of ambient temperature on structures dynamic characteristics and to differentiate the patterns of mode shape changes caused by damage and ambient temperature. It was concluded that the change of ambient temperature mainly affects the elastic modulus of the construction materials and therefore stiffness of the entire bridge. As a result, the eigenfrequencies and mode shapes of the structure are influenced.<p> The dynamic properties extracted from measured experiment data showed an approximately bilinear relationship between the three first natural frequencies and the ambient temperature. The natural frequencies for all three modes increased when the temperature fell.<p> It was also found that, conceptually, it is possible to distinguish the patterns of mode shape changes caused by small-scale damage from those due to thermal effects, but only if a sufficient number of sensors are used to measure the mode shapes; in addition, those sensors must be located close to the damage location.

The aim of this thesis was to use long-term sewage sludge application to land to determine if sludge, particularly metal-rich sludge, alters the microbial community as indicated by substrate utilisation profiles (sups), using the Biolog ^TM method.  An additional aim was to assess Biolog^TM as a rapid method of monitoring soil health. Sludge rich in Cadmium altered microbial community profiles, but this was possibly due to differences in organic Carbon quality between sludges used in the trial.  Conditioning (incubation) of soils before analysis with Biolog^TM made these effects more apparent.  Storage of soil also altered microbial activity and community profiles, which were not restored by a conditioning period.  Both incubation and storage influenced the Biolog^TM response and can potentially affect available soil C. Therefore, the effects of organic matter application at high levels on the microbial community, were assessed without metals.  Low metals sludge altered microbial community function, although the trends were not consistent across soil types.  Biolog^TM was more sensitive to sludge treatment effects than total microbial biomass C. The microbial community responses to sludge and preparation disturbance were examined (using Biolog^TM and microbial PLFAs). A method to determine extractable carbohydrates was adapted for use in a microplate format, and was employed to assess the relationship between microbial community change and available soil C.  Changes in soil microbial community structure and function were not related to extractable carbohydrate C.  Biolog^TM and PLFA responded differently:  disturbance had a greater effect on Biolog response than either application of sewage sludge or the quality of soil C;  but PLFAs were more affected by long-term sewage sludge amendment, highlighting implications for the monitoring of waste-amended soils.

No description available.

The purpose of this dissertation is to demonstrate the ability to design health monitoring systems from a systematic perspective and how, with proper sensor and actuator placement, damage occurring in a structure can be detected and tracked. To this end, a design optimization was performed to determine the best locations to excite the structure and to collect data while using the minimum number of sensors. The type of sensors used in this design optimization was uni-axis accelerometers. It should be noted that the design techniques presented here are not limited to accelerometers. Instead, they allow for any type of sensor (thermal, strain, electromagnetic, etc.) and will find the optimal locations with respect to defined objective functions (sensitivity, cost, etc.). The use of model-based optimization techniques for the design of the monitoring system is driven by the desire to obtain the best performance possible from the system given what is known about the system prior to implementation. The use of a model is more systematic than human judgment and is able to take far more into account by using information about the dynamical response of a system than even an experienced structural engineer. It is understood in the context of structural modeling that no model is 100\% accurate and that any designs produced using model-based techniques should be tolerant to modeling errors. Demonstrations performed in the past have shown that poorly placed sensors can be very insensitive to damage development. To perform the optimization, a multi-objective genetic algorithm (GA) was employed. The objectives of the optimization were to be highly sensitive to damage occurring in potential “hot spots” while also maintaining the ability to detect damage occurring elsewhere in the structure and maintaining robustness to modeling errors. Two other objectives were to minimize the number of sensors and actuators used. The optimization only considered placing accelerometers, but it could have considered different type of sensors (i.e. strain, magneto-restrictive) or any combination thereof.

In any infrastructure project, monitoring and managing the built assets is an important task. Structural Health Monitoring (SHM) is meant for continuous assessment of safety and serviceability of a structure and its elements. SHM has taken a leading role in the field of structural engineering and has become very popular in recent age. Bridge deflection is the basic evaluation index to examine the health status of a bridge structure. The existing bridge monitoring systems have several drawbacks. Hence, a new methodological approach has been proposed to overcome the limitations of traditional contact-based bridge deflection monitoring system and other non-contact based system. This study developed a non-contact linear feature based Deflection Monitoring System (DMS) using Terrestrial Laser Scanning (TLS) and cameras for timber railroad bridges. The process and detailed workflow of building the DMS, its components and sensors involved are discussed here. The efficiency of this DMS is validated against a deflectometer. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

No description available.

Structural Health Monitoring (SHM) is the process of monitoring the state of a structure to determine the existence, location, and degree of damage that may exist within the entire structure. A structure’s health or level of damage can be monitored by identifying changes in structural or modal parameters. In this research, the structure’s health is monitored by identifying changes in structural stiffness. The Adaptive Least Mean Square (LMS) filtering approach is used to directly identify changes in structural stiffness for the IASC-ASCE Structural Health Monitoring Task Group Benchmark problem for both Phase I and II. The research focuses primarily on Phase II of the benchmark problem. In Phase II, modeling error and noise is introduced to the problem making the problem more realistic. The research found that the LMS filter approach can be used to detect damage and distinguish relative severity of the damage in Phase II of the benchmark problem in real time. Even though the LMS filter approach identified damage, a threshold below which damage is hard to identify exists. If the overall stiffness changes less than 10%, then identifying the presence and location of damage is difficult. But if the time of damage is known, then the presence and location can be determined. The research is of great interest to those in the structural health monitoring community, structural engineers, and inspection practitioners who deal with structural damage identification problems.