Saskatchewan Highways and Transportation (SHT) is responsible for 26,125 km of highways in the province. The highway system is divided into primary and secondary highways. The primary highway system provides an inter-regional, inter-provincial, and inter-national highway network that was built to accommodate traffic volumes in excess of 4,000 vehicles per day with significant numbers of heavily loaded trucks. The secondary highway system consists of structural, thin membrane surface (TMS), and gravel highways. TMS highways were constructed to provide feeder links into the primary system for relatively low volumes of traffic with few heavily loaded trucks. Years of increasing volumes of heavy trucks and inadequate funding on the TMS highway system have forced SHT to evaluate various management strategies. New maintenance and management strategies like partnerships with Rural Municipalities and full depth in-place chemical strengthening have been developed and, along with conventional management strategies, are being used throughout Saskatchewan. The purpose of this research is to develop a project level analytical framework capable of evaluating management strategies for secondary highways, based on SHT surfacing and structure standards. The best management strategy is the lowest total cost strategy (agency and road user) based on SHT standards. Probabilistic modeling was also included in the framework so uncertainty in the variables, like length of the service life of these new strategies, could be analyzed. A project on Highway No. 19 was evaluated to demonstrate the framework. From the analysis, the full depth in-place chemical strengthening was the preferred strategy if it lasted 15 to 20 years, relative to a 15 year expected life of the conventional strategy. As well, as the technology advances in Saskatchewan, it appears that the full depth in-place chemical strengthening should decrease in cost while the conventional strategy increases in cost as aggregate sources are depleted. This trend should result in long-term cost savings to SHT.

Saskatchewan Highways and Transportation (SHT) is responsible for 26,125 km of highways in the province. The highway system is divided into primary and secondary highways. The primary highway system provides an inter-regional, inter-provincial, and inter-national highway network that was built to accommodate traffic volumes in excess of 4,000 vehicles per day with significant numbers of heavily loaded trucks. The secondary highway system consists of structural, thin membrane surface (TMS), and gravel highways. TMS highways were constructed to provide feeder links into the primary system for relatively low volumes of traffic with few heavily loaded trucks. Years of increasing volumes of heavy trucks and inadequate funding on the TMS highway system have forced SHT to evaluate various management strategies. New maintenance and management strategies like partnerships with Rural Municipalities and full depth in-place chemical strengthening have been developed and, along with conventional management strategies, are being used throughout Saskatchewan. The purpose of this research is to develop a project level analytical framework capable of evaluating management strategies for secondary highways, based on SHT surfacing and structure standards. The best management strategy is the lowest total cost strategy (agency and road user) based on SHT standards. Probabilistic modeling was also included in the framework so uncertainty in the variables, like length of the service life of these new strategies, could be analyzed. A project on Highway No. 19 was evaluated to demonstrate the framework. From the analysis, the full depth in-place chemical strengthening was the preferred strategy if it lasted 15 to 20 years, relative to a 15 year expected life of the conventional strategy. As well, as the technology advances in Saskatchewan, it appears that the full depth in-place chemical strengthening should decrease in cost while the conventional strategy increases in cost as aggregate sources are depleted. This trend should result in long-term cost savings to SHT.

The use of externally bounded Carbon Fiber Reinforced Polymer (CFRP) for strengthening existing RC structures has shown promising results. Although CFRP materials have high tensile strength, the ability to utilize that strength is limited by debonding of the CFRP laminates from the concrete surface. In order to prevent or delay debonding, CFRP anchors were used to provide an alternative means of transferring forces from CFRP strips to the concrete. Previous tests on prestressed I-girders strengthened with uni-directional and bi-directional CFRP strips showed that bi-directional CFRP application resulted in significant shear strength gain in comparison to a uni-directional application. The objective of this thesis is to evaluate the behavior of reinforced concrete beams strengthened in shear with bi-directional CFRP strips and CFRP anchors so that the findings from the previous work can be understood and implemented. Four 24 in. deep T-beams were fabricated at the Phil M. Ferguson Structural Engineering Laboratory at The University of Texas at Austin. Eight tests were conducted on these specimens to examine the effect of the bi-directional layout of CFRP on the shear strength. Specimens with 14-in. web width were selected as a part of the experimental program to allow for direct comparison with test results from the previous project. Additional beams with a web width of 8 in. were included to evaluate thinner webs similar to those in the I-girders. Test results indicate a significant increase in shear strength due to the bi-directional application of CFRP strips with CFRP anchors installed on beams with a shear span-to-depth ratio (a/d) of 3. Substantial shear strength gain up to 62% was achieved in beams with 14-in. webs. and up to 43% for beams with 8-in. webs. However, negligible shear strength gain was observed in beams with a/d of 1.5 (deep beams). Experimental test results demonstrate an interaction between the contribution of concrete, transverse steel and CFRP to the shear resistance of a reinforced concrete beam. The findings of this research contribute to a better understanding of the shear behavior of reinforced concrete members strengthened with externally bonded CFRP applied bi-directionally. Experimental results from this research project provide data needed in the field of CFRP shear strengthening since limited data are available on large-scale tests. / text

As the world energy demand increases, drilling deeper wells is inevitable. Deeper wells have abnormal pressure zones where the difference between pore pressure and fracture pressure gradient, is very small. Smaller drilling margins make it harder to drill the well and result in high operation costs due to the increase of non-productive time. One of the major factors influence non-productive time in drilling operations is lost circulation due to drilling induced fractures. The most common approach is still plugging the fractures by using various loss circulation materials and there are several wellbore strengthening techniques present in the literature to explain the physics behind this treatment. This thesis focuses on development of a rock mechanics/hydraulic model for quantifying the stress distribution around the wellbore and fracture geometry after fracture initiation, propagation and plugging the fracture with loss circulation materials. In addition, fracture behavior is investigated in different stress states, for different permeability values and in the presence of multiple fractures. The following chapters contain detailed description of this model, and analysis results. / text

No description available.

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (ℓ. 156-170)

The success in fabrication of various nano-sized powders, wires or tubes has arisen the new possibility in modifying the existing commercial materials in terms of their functional or structural characteristics. In this study, the AZ61 Mg alloy is adopted as the matrix, and nano-sized SiO2 particulates are introduced into the alloy by means of casting, powder metallurgy, or spray forming processes to fabricate a high performance Mg matrix composite. The strengthening mechanisms, fracture toughness and bending toughness of the AZ61 Mg based composites are examined. The composites were prepared either by spray forming, ingot metallurgy, or powder metallurgy, followed by severe hot extrusion. The spray formed composites exhibit the best nano particle distribution and toughness, but the volume fraction of the nano particles that can be inserted is limited. The nano composites fabricated through the powder metallurgy method possess the highest strength due to the extra strengthening effect from the MgO phase. Strengthening analysis based on the Orowan strengthening mechanism can predict well the composite strength provided that the nano particles are in reasonably uniform dispersion. For composites containing higher nano particle volume fractions greater than 3%, the experimental strength data fall well below the theoretical predictions, suggesting poor dispersion of the reinforcement. The creep properties of the composites are also explored. The specimens are subjected to tensile loading at temperatures 200 to 400oC and strain rates 1x10-3 to 1x10-1. The creep mechanism is identified as dislocation creep controlled with the rate controlling diffusion step being the magnesium lattice diffusion at low strain rates and grain boundary diffusion at high strain rates.

No description available.

Ein Ziel des Sonderforschungsbereiches 528 war, das Verbundsystem auf allen Skalenebenen so präzise beschreiben zu können, dass eine hinreichende Genauigkeit bei der Berechnung des Tragverhaltens von Stahlbetonbauteilen mit Textilbetonverstärkung nicht nur bei der Nachrechnung, sondern auch bei der Prognose erreicht wird. Die Vorhersagequalität von Tragfähigkeiten für die Biege-, Querkraft- und Normalkraftverstärkung wurde mit Hilfe von Großversuchen nachgewiesen, deren Ergebnisse vor der Berechnung nicht bekannt waren. Anhand der bereitgestellten Materialparameter und Geometriedaten wurde in den numerischen Teilprojekten sowie in einem experimentell orientierten Teilprojekt das Tragverhalten prognostiziert. Danach wurden die Versuche durchgeführt. Die prognostizierten Traglasten wurden durch die Experimente bestätigt. Der vorliegende Beitrag fokussiert auf die Querkraftverstärkung, da eine detaillierte Beschreibung aller Versuche den Rahmen sprengen würde. / One aim of the developments in the SFB 528 was the description of the compound system as precisely as possible at all scale levels that an adequate precision is not achieved by reinforced concrete components at the calculation of the load carrying behaviour with TRC reinforcements only at the historical calculation but also at the forecast. The forecast quality of load-capacities for the bend, shear and normal force strengthenings was proved with the help of large-scale experiments whose results were not confessed before the calculation. With the provided material parameters and geometry data the load carrying behaviour was forecast in the numeric subprojects as well as in an experimentally oriented subproject. After that the tests were carried out. The forecast loads were confirmed by the experiments. The paper on hand focuses on the shear strengthening since a detailed description of all tests would go beyond the scope.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 313-321). Available also in a digital version from Dissertation Abstracts.