Theses and Dissertations at Montana State University (MSU)
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Item Performance of FRP-strengthened reinforced concrete beams subjected to low temperature(Montana State University - Bozeman, College of Engineering, 2021) Ahmed, Emtiaz; Chairperson, Graduate Committee: Kirsten MattesonThe use of Fiber Reinforced Polymer (FRP) to repair and strengthen existing concrete structural elements (beams, columns, beam-column connections, and slabs) has become globally accepted and popular. FRP can be used for this application in several forms, such as externally applied wrapping, Near Surface Mounted (NSM) bars, lamination, and sheets. The strength to weight ratio of this material is one of the main criteria that makes this material approved and desired by engineers and researchers for this application. Also, FRP is corrosion resistant and requires less installation time compared to other repairing techniques such as jacketing, section enlargement, and external post tensioning. The performance of FRP repairs has been studied extensively at conventional, non-extreme temperatures; however, little research has been conducted on the performance of these repairs at cold temperatures. The research discussed herein aims to fill this gap in knowledge so that FRP repairs can be more widely used in cold temperature environments, such as for bridge repairs in the state of Montana. In this work, six beams (6 in. x 8 in., 10 ft long) were constructed and tested in four-point bending at two different temperatures (room temperature and -40 °C). For each temperature, there were three beam types: 1) a control beam, 2) a longitudinal strengthened beam, and 3) a longitudinal + transverse strengthened beam. Overall, the results showed that low temperatures have a generally positive effect on concrete strength and beam performance. The average concrete compressive strength of frozen cylinders at -40 °C was observed to be 87.18% higher than the cylinders tested at room temperature. For all beam types, the ultimate load carrying capacity of the low temperature beams exceeded the capacity of the counterpart beam tested at room temperature. Additionally, at lower temperatures the strengthened beams showed delayed FRP delamination (occurring at higher displacements). Further, the initial stiffnesses of the cold beams were found to be significantly higher than the room temperature beams. Overall, the results of this study are promising for the potential of use of FRP for repairs in cold environments and future research is warranted.Item Resistance temperature devices fabricated using micro electromechanical systems technology designed and characterized for low-temperature applications(Montana State University - Bozeman, College of Engineering, 2020) Thomae, Madelyn Ruth; Chairperson, Graduate Committee: Stephan WarnatResearch shows that microorganisms play a major role in climate change, but there is a lack of adequate understanding of microbial involvement in climate change and further research is needed for greater understanding. Temperature monitoring lends an insight into the current climatic shifts in Arctic and Antarctic regions. Currently, satellite monitoring is used to track temperature changes in those regions. To further the understanding of the role microorganisms play in the rising temperatures in those regions, in-situ temperature monitoring is needed. Commercially available temperature probes are high in cost and not well-suited for the harsh environment of Arctic and Antarctic regions. Utilizing micro electromechanical systems technology provides a solution for robust low-cost, low-power sensors that can be designed specifically to operate in harsh environments. Gold resistance temperature devices were designed and fabricated using micro electromechanical systems technology with a high spatial resolution capable of detecting microorganisms in subzero applications. The fabricated temperature sensors were calibrated for subzero use and freezing experiments were done to detect any changes due to impurities in the sample. The gold resistance temperature devices were able to withstand prolonged exposure to the harsh experimental environment and provide an accurate spatial temperature gradient throughout the media. The gold resistance temperature devices had negligible effects due to the self-heating phenomenon common in resistance temperature devices. Additionally, the sensors were able to detect variations in the freezing curve of the media with the inclusion of the bacterial isolate Flavobacterium sp. ANT 11 (accession number GU592435) in DI water samples. Future research should focus on (1) furthering the understanding of the microbial interactions in the cooling curves of different medias and (2) integrating electrical impedance spectroscopy sensors to provide knowledge of what impurities are in the sample that could be affecting the freezing curve of the media.Item Operating characteristics and calibration of thermocouple psychrometers at low temperatures and potentials near zero(Montana State University - Bozeman, College of Agriculture, 1975) Degn, Roy Madsen