The objective of the research presented in this thesis was to study and optimize the transverse deck reinforcement for a skewed concrete bridge deck supported by Hybrid Composite Beams (HCB's).  An HCB consists of a Glass Fiber Reinforced Polymer outer shell, a concrete arch, and high strength seven wire steel strands running along the bottom to tie the ends of the concrete arch together.  The remaining space within the shell is filled with foam.  The concrete arch does not need to be cast until the beam is in place, making the HCB very light during shipping.  This lowers construction costs and time since more beams can be transported per truck and smaller cranes can be used.  HCB's are quite flexible, so AASHTO LRFD's design model for bridge decks, as a one-way slab continuous over rigid supports, might not apply well to the HCB's deck design. A skewed three HCB girder bridge with a reinforced concrete deck and end diaphragms was built in the laboratory at Virginia Tech.  Concentrated loads were applied at locations chosen to maximize the negative and positive moments in the deck in the transverse direction.  The tests revealed that the transverse reinforcement was more than adequate under service loads. An Abaqus model was created to further study the behavior of the bridge and to help create future design recommendations.  The model revealed that the HCB bridge was behaving more like a stiffened plate at the middle section of the bridge, indicating that the flexibility of the girders needed to be considered. / Master of Science

Millions of people in low-lying areas are already affected by flooding, and the number will increase substantially in the future. Tidal flooding, the form of flooding caused by a combination of high tides and sea level rise to overcome protection levels, can cause damage and inconveniences such as road closures, overwhelmed drainage systems, and infrastructure deterioration from water damage. Tidal flooding already occurs annually in cities along the U.S. east coast, most notably Miami. However, the time it will take for other regions globally to begin to experience tidal flooding has not yet been assessed. Therefore, there is a limited understanding of how and when human populations will be exposed to this type of flooding. Tide gauge data from the GESLA-2 data base are used to obtain information about the highest astronomical tide (HAT) and extreme value statistics for 571 locations globally. For a complete spatial analysis, modelled water levels from the Global Tide and Surge Reanalysis (GTSR) are also used. Estimated protection levels are extracted from the DIVA database and translated to absolute heights based on the extreme value statistics of high water levels. This analysis is based on calculating the difference between the existing protection level and HAT, which indicates how much sea levels can rise before tidal flooding occurs, and evaluating in what decade this is expected to happen under different sea-level rise (SLR) scenarios. Tidal trends from the nodal and perigean are also taken account and used to modify 1000 different sea level rise scenarios to provide a more comprehensive analysis of possible tidal flooding years. Our results indicate that tidal flooding may occur within a few decades in many locations (under the assumption that no adaptation will take place), and therefore awareness should be heightened so that actions can be taken to minimize the impacts.

No description available.

A test program for the Hybrid-Composite Beam (HCB) was conducted prior to its use for the replacement of a skewed, simply-supported bridge (Tide Mill Bridge). The HCB is an innovative combination of conventional materials and ideas in a structural beam. The beam consists of a concrete arch tied with prestressing strand that is placed within a Fiber-Reinforced Polymer (FRP) box. Behavior in individual HCB's and a three HCB-system was examined to determine the appropriateness of the current design methodology developed by John Hillman and the simplifying assumptions made within it. Such assumptions include strain compatibility and linear-elastic behavior. Three HCB's were tested at the structures laboratory at Virginia Tech. During individual beam tests, the predicted behavior of the FRP box and prestressing strand agreed with experimental results. The tests revealed the arch was susceptible to local bending and behaved far differently from predicted. Overall, the beams were shown to behave linearly. A final test was performed to apply the design live load to the system. Slight non-linear behavior was observed in the beams. Distribution factors for the system were also investigated and compared to AASHTO and Hillman's model. AASHTO factors were conservative for exterior girders but unconservative for interior girders. Hillman's factors were often conservative but were in agreement for the shear in the exterior girder. The current design procedure appeared to predict FRP and strand behavior well, but the behavior of the arch appeared to differ greatly from the other components of the HCB. / Master of Science

Thesis (M. Phil.)--University of Hong Kong, 1991.

Wong Chun Kwan. / "June, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 211-231). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

While community ecologists have traditionally focused on local-scale processes, it has become apparent that a broader perspective, which explores the community-level ramifications of material fluxes within and between ecosystems, is necessary to effectively evaluate bottom-up influences on community structure and dynamics. In this dissertation, I employed ecosystem principles to understand these processes in rocky intertidal communities. I specifically examined the roles of sessile invertebrates in mediating the transfers and transformations of carbon and nitrogen in intertidal ecosystems. First, I quantified the links between nearshore pelagic and rocky intertidal systems. By assimilating suspended particulate organic material (seston), mussels and other sessile invertebrates serve as mediators of material exchange from pelagic to benthic ecosystems. I evaluated these trophic linkages along productivity gradients on the coasts of New Zealand and Oregon, which allowed me to address the influences of seston quality and quantity on the growth and ammonium excretion rates of mussels. My results highlight the necessity of simultaneously considering both seston quantity (total organic particulates) and quality (phytoplankton availability) in evaluating benthic-pelagic coupling. Second, I assessed the utilization of invertebrate-excreted ammonium by macroalgae in high-intertidal pools. Sessile invertebrates not only serve as mediators of material transfer into intertidal ecosystems, they also chemically transform that material, converting particulate organic nitrogen, which is unusable by macroalgae, into ammonium, which algae readily assimilate. l showed that especially in high-zone pools, which are isolated from the ocean for 80% of the time, invertebrate-excreted ammonium is an important nitrogen source for macroalgae. Ammonium accumulated in tide pools and was subsequently taken up by algae. This novel positive interaction influenced community structure: macroalgal species richness increased with the rate of invertebrate-mediated ammonium loading in pools. Finally, by experimentally manipulating macroalgae and invertebrates in laboratory mesocosms, I quantified the effect of ammonium loading on algal growth. I demonstrated that algal nitrogen assimilation rates increased with the rate of ammonium accumulation in tide pools, which resulted in enhanced growth when invertebrates were present. Together, these studies suggest that by merging community and ecosystem perspectives we can gain unique and important insights into the bottom-up processes influencing intertidal systems. / Graduation date: 2004

Les estimations de la remontée générale du niveau de la mer, de l’ordre de 17 ± 2 cm sur le siècle dernier, masquent une réalité très variable d’une région à l’autre. Qu’en est-il du littoral charentais ? Des séries temporelles de plus de 40-50 ans sont souvent indispensables pour tirer des tendances fiables à long terme sur les composantes du niveau marin : niveau moyen de la mer, ondes de marée et effets météorologiques. Or, de nombreux lots de mesures marégraphiques du littoral charentais « sommeillaient » dans les centres d’archive français, i.e. : La Rochelle-Vieux port (1775-1892), La Rochelle-La Pallice (1885-auj.), île d’Aix (1824-auj.), fort Enet (1859-1873), fort Boyard(1873-1909) et Cordouan (1812-1994). Les objectifs de nos travaux de recherche étaient multiples : inventorier,sauvegarder et numériser des lots de mesures historiques du niveau marin, puis construire des séries temporelles recomposées à partir de ces lots de mesures hétérogènes, temporellement et spatialement, et enfin les exploiter pour mieux décrire et comprendre l’évolution à long terme du niveau de la mer. La qualité des trois séries construites (LaRochelle : 1775-auj. ; Aix-Enet-Boyard : 1824-auj. ; et Cordouan : 1812-1994) a ensuite été éprouvée en détail afin d’évaluer le niveau de précision de notre reconstruction. A partir de ces séries inédites, nous avons pu étudier l’évolution des composantes du niveau marin. Suite à ces travaux, nous fournissons un inventaire le plus exhaustif possible détaillant les mesures de 25 observatoires de Charente-Maritime, de 1775 à aujourd’hui. Les données des séries temporelles ainsi que des éléments permettant d’apprécier leur qualité seront bientôt disponibles en ligne sur REFMAR (refmar.shom.fr), SONEL (www.sonel.org) et au PSMSL (www.psmsl.org). Nos résultats positifs nous ont permis de reconstruire une série encore plus globale, celle du pertuis d’Antioche, à partir des moyennes mensuelles du niveau marin des séries de La Rochelle et d’Aix-Enet-Boyard. Parmi les résultats marquants obtenus,le niveau moyen de la mer s’est élevé de +1,38 ± 0,08 mm/an dans le pertuis d’Antioche sur la période 1860-2010.Ce résultat est cohérent avec Liverpool (+1,2 ± 0,1 mm/an sur la période 1858-1997 [Woodworth, 1999a]) et avec les récents résultats suggérant que l’élévation du niveau marin sur les côtes atlantiques européennes est moins importante qu’au niveau mondial (+1,7 ± 0,3 mm/an sur la période 1870-2004 [Church & White, 2006]). / Global sea level rise, which is estimated at 17 ± 2 cm over the last century, does not reflect the differences of the sealevel evolution between places across the world. What is the situation along the Charente-Maritime French Atlanticcoast? Time series covering a period of at least 40-50 years are vital to establish reliable long-term trends of sealevel components: mean sea level, tidal constituents and meteorological effects. Many tide gauge data sets of the Charente-Maritime coast have recently been rediscovered in archives: La Rochelle-Vieux port (1775-1892), La Rochelle-La Pallice (1885-today), île d’Aix (1824-today), fort Enet (1859-1873), fort Boyard (1873-1909) and Cordouan (1812-1994). The aims of this thesis were firstly to inventory, to rescue and to digitize historical sea leveldata sets. Secondly, those data sets were put back together in order to construct continuous time series, which have been analysed and led to a better description of long-term sea level changes. In this way, three time series were constructed (La Rochelle: 1775-today; Aix-Enet-Boyard: 1824-today; and Cordouan: 1812-1994) and have been deeply examined to assess the construction validity and quality. From these new time series, we could estimate changes of sea level components. Thanks to this research work, we have been able to provide an inventory as exhaustive as possible, with detailed measurements of twenty five Charente-Maritime’s stations from 1775 to nowadays. All those data will be soon available on REFMAR (refmar.shom.fr), SONEL (www.sonel.org) and PSMSL (www.psmsl.org) websites. From those positive results, we have been able to reconstruct a more global time series (Pertuis d’Antioche) from the monthly mean sea levels of La Rochelle and Aix-Enet-Boyard. Among our results, we can high light that the mean sea level trend on Pertuis d’Antioche is estimated at +1.38 ± 0.08 mm/year, from 1860 to 2010. This result is consistent with Liverpool’s trend (+1.2 ± 0.1 mm/year from 1858 to 1997[Woodworth, 1999a]) and also with recent results suggesting that sea level rise along the European Atlantic coasts isslower than global sea level rise (+1.7 ± 0.3 mm/year from 1870 to 2004 [Church & White, 2006]).

Social Science scholars study how the New Left - the wave of leftist governments in Latin America since 1999 - redefines leftism in the Post-Cold War. Part of this redefinition is a new social pact between the Queer community and those Latin American governments. Chapter 1 traces the ideological itinerary of this new social agreement and establishes the methodology of the study. El lobo, el bosque y el hombre nuevo (The Wolf, the Forest and the New Man) by Senel Paz reformulated the relationship between the dissident subjects of the patriarchy and the leftist state in Cuban society of the 1990s. Chapter 2 highlights Paz's text for its separation from the Cold War narratives centered on the leftist armed insurgent movements. Chapter 3 studies how the film adaptation of Paz's work globalized the argument and structured it within the Post-Cold War. Chapter 4 analyzes the theatrical adaptations of Paz's work made in Latin American countries after 1999. Two are compared from countries with New Latin American Leftist governments, Venezuela and Argentina, with others made in non-Latin American countries, the United States and Spain. The critical reception of the two theatrical adaptations done in Latin America showed the argument as part of their reality, in contrast to the representations made in the United States and Spain. Chapter 5 analyzes the repercussions of Paz's text in popular culture through the reggaeton "Fresa y chocolate."

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management