Browsing by Subject "Repair"
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Item Acoustic Emission Monitoring of Fatigue Cracks in Steel Bridge Girders(Minnesota Department of Transportation, 1999-09) McKeefry, Jay A.; Shield, Carol K.This report presents results from a laboratory study and field implementation of acoustic emission monitoring of fatigue cracks in cover-plated steel bridge girders. The acoustic monitoring successfully detected growing fatigue cracks in the lab when using both source location and a state of stress criteria. Application of this methodology on three field bridges also proved successful by detecting a propagating crack in two of the bridges and an extinguished crack in a third bridge. Researchers tested a double angle retrofit, designed by the Minnesota Department of Transportation, both in the lab and in the field of girder with fatigue cracks in the top flange. This retrofit does not require removal of concrete deck, and only involves bolting the retrofit to the bridge girder web. The double angle retrofit applied to laboratory test girder resulted in a reduction of flange stresses by 42 percent. Field implementation of the retrofit had mixed success. On one bridge, stress ranges in the cracked flange was reduced by 43 percent. However, on a second test bridge, the reduction was only 8 percent, likely due to the inadequate space for proper installation of the retrofit.Item Circuits of capital: India’s electronic waste in the informal global economy(2018-08) Corwin, JuliaElectronics are rife with significance to the complex workings of the global economy: commodity circuits to produce devices like personal computers and smartphones include materials mined and manufactured from across the globe, and the recycling and disposal of these commodities has attracted significant attention due to globe-trotting electronic wastes (e-waste) as well. This dissertation begins and ends with contemplating Delhi’s diverse e-waste industries as part of the global economy, with ramifications for both the Delhi-based workers themselves and the circuits of capital in which they operate. Against the common discourse on informal electronic waste recycling labor in India as crude, polluting and hazardous work, my research argues that this local industry is rooted in the creative reinvention of electronics and their reentry into commodity circuits, rather than their disposal. I demonstrate how Delhi’s organized and uniquely efficient informal secondary use electronics industries provide environmental services for the city as well as the immaterially and materially interconnected world. This inventive repair work exists in what is otherwise conceived of as a world in the digital ‘cloud,’ the ephemeral and immaterial world of the human mind and the computer processor. Revaluing supposedly local, used and non-corporate secondary use electronics labor reveals the politics behind electronic waste management, in which access to e-waste as a valuable ‘urban’ mine is fought over through environmental governance and corporate campaigns. By understanding supposedly local electronics repair work as inseparable from global economic processes, these electronic circuits of capital reveal the global economy to be densely connected and fundamentally informal, based in a variety of illegal, legal-adjacent, unauthorized and unregulated business practices that form the backbone of India’s electronics industry. Rather than the informal sector and informal labor representing the forgotten underbelly of global consumption, I argue that not only is global trade and corporate capital dependent on informality but it is intimately entrenched in this informality as a basis for ensuring smooth capital flows. The circuits of capital are connected through the processes of moving materials both across categories (of waste/value, informal/formal, non-corporate/corporate, non-capital/capital) and across places in the world. All this positions the informal work of waste not as peripheral or ancillary to global capitalism but right in the middle of it all, enabling its flows of supply and demand through the wastage of materials along with their informal trade networks. In this way, the work of waste is not just a facilitator of global electronics production, consumption and trade but illustrative of the norms and functions of global capitalism as rooted in waste production, subterranean pathways and salvage accumulation.Item Effect of FRCM Repair on the Bond Behavior of Corroded Reinforced Concrete Beams Subjected to Static and Cyclic Loading(2017-08) Anderson, MirandaThis paper presents the evaluation of the effectiveness of Fiber Reinforced Cementitious Matrix (FRCM) repair in improving the bond behavior of corroded reinforced concrete beams under both static and fatigue loading. The study consisted of 30 full-scale beams, both corroded and uncorroded. The variables used in this study were corrosion level based on mass loss, repair method used, type of loading (monotonic or repeated loading), and load range applied. Corrosion was found to reduce the fatigue strength of reinforced concrete beams by introducing internal stresses in the concrete that ultimately cause reduction in the bond between the reinforcement and the surrounding concrete. FRCM was found to increase the fatigue strength of corroded concrete beams by providing confinement, thus making it an effective method for repairing beams damaged from corrosion. The use of a cementitious substrate with FRCM allowed for easier monitoring of the cracks developed in the concrete while testing.Item Protein expression profile of rat type two alveolar epithelial cells during hyperoxic stress and recovery(2013-05) Bhargava, ManeeshRationale: In rodent model systems, the sequential changes in lung morphology resulting from hyperoxic injury are well characterized, and are similar to changes in human acute respiratory distress syndrome (ARDS). In the injured lung, alveolar type two (AT2) epithelial cells play a critical role restoring the normal alveolar structure. Thus characterizing the changes in AT2 cells will provide insights into the mechanisms underpinning the recovery from lung injury. Methods: We applied an unbiased systems level proteomics approach to elucidate molecular mechanisms contributing to lung repair in a rat hyperoxic lung injury model. AT2 cells were isolated from rat lungs at predetermined intervals during hyperoxic injury and recovery. Protein expression profiles were determined by using iTRAQ® with tandem mass spectrometry. Results: Of 959 distinct proteins identified, 183 significantly changed in abundance during the injury-recovery cycle. Gene Ontology enrichment analysis identified cell cycle, cell differentiation, cell metabolism, ion homeostasis, programmed cell death, ubiquitination, and cell migration to be significantly enriched by these proteins. Gene Set Enrichment Analysis of data acquired during lung repair revealed differential expression of gene sets that control multicellular organismal development, systems development, organ development, and chemical homeostasis. More detailed analysis identified activity in two regulatory pathways, JNK and miR 374. A Short Time-series Expression Miner (STEM) algorithm identified protein clusters with coherent changes during injury and repair. Conclusion: Coherent changes occur in the AT2 cell proteome in response to hyperoxic stress. These findings offer guidance regarding the specific molecular mechanisms governing repair of the injured lung.