Testing and Development of Pre-Stressed CFRP Retrofit Strategies for Controlling Fatigue Cracking in Steel Waterway Lock Gate Structures

Steel waterway lock gates across the national inland waterway transportation network are reaching and exceeding their intended service life, often experiencing component failures that lead to service interruptions. Unscheduled maintenance and repair of lock gates can be expensive and cause economic ripples throughout the entire inland waterway network. These lock gate component failures are often caused by fatigue cracking from repeated loading during operation. This thesis develops and tests a prestressed carbon fiber reinforced polymer (CFRP) fatigue retrofit for controlling fatigue demands within lock gate components. The study expands upon a recent analytical work by Lozano (2017) by experimentally investigating prestressing strategies, bonding mechanisms, prestress creep/relaxation performance, and large-scale experimental fatigue testing. A total of seven large-scale cyclic tests were conducted on lock gate components (with and without applied retrofits) to gauge the effectiveness of the developed prestressing strategies. All gate specimens tested were artificially notched to create a local stress concentration and worsened fatigue condition. Results indicate that the addition of the prestressed CFRP retrofit increases the fatigue life of the retrofitted gate component despite the prestress loss due to epoxy adhesive debonding following rapid cyclic loading. The retrofitted specimen experienced a fatigue life increase of nearly 3 times over the un-retrofitted specimen. Additionally, load shedding into the CFRP, even without significant prestress applied, contributes to a reduction in the component notch stress. The applied CFRP clamping force is able to provide enough force transfer to the CFRP to reduce the notch local stresses

The Kingdom of God as Relation

The author describes the theory of an emerging interdisciplinary field called \'ecological science,\' the study of which leads to innovative ideas about the nature of God

Metallothionein as an indicator of water quality: assessment of the bioavailability of cadmium, copper, mercury and zinc in aquatic animals at the cellular level

The study of metallothioneins (MTs) has greatly improved our understanding of body burdens, metal storage and detoxification in aquatic organisms subjected to contamination by the toxic heavy metals, Cd, Cu, Hg and Zn. These studies have shown that in certain organisms MT status can be used to assess impact of these metals at the cellular level and, whilst validation is currently limited to a few examples, this stress response may be linked to higher levels of organisation, thus indicating its potential for environmental quality assessment. Molluscs, such as Mytilus spp., and several commonly occurring teleost species, are the most promising of the indicator species tested. Natural variability of MT levels caused by the organism's size, condition, age, position in the sexual cycle, temperature and various stressors, can lead to difficulties in interpretation of field data as a definitive response-indicator of metal contamination unless a critical appraisal of these variables is available. From laboratory and field studies these data are almost complete for teleost fish. Whilst for molluscs much of this information is lacking, when suitable controls are utilised and MT measurements are combined with observations of metal partitioning, current studies indicate that they are nevertheless a powerful tool in the interpretation of impact, and may prove useful in water quality assessment

Turbine endwall two-cylinder program

Progress is reported in an effort to study the three dimensional separation of fluid flow around two isolated cylinders mounted on an endwall. The design and performance of a hydrogen bubble generator for water tunnel tests to determine bulk flow properties and to measure main stream velocity and boundary layer thickness are described. Although the water tunnel tests are behind schedule because of inlet distortion problems, tests are far enough along to indicate cylinder spacing, wall effects and low Reynolds number behavior, all of which impacted wind tunnel model design. The construction, assembly, and operation of the wind tunnel and the check out of its characteristics are described. An off-body potential flow program was adapted to calculate normal streams streamwise pressure gradients at the saddle point locations