Browsing by Subject "Fiber"
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Item Analytical and Experimental Assessment of an AASHTO I-girder Type I Prestressed with AFRP Tendons(2014-12-12) Cummings, Wesley DavidCorrosion induced deterioration is one of the main reason for repair and rehabilitation programs in conventional steel reinforced concrete bridge decks. Of all bridges in the United States, over 50 percent are constructed of conventional reinforced or prestressed concrete (NACE, 2013), where one in three bridges are considered structurally deficient or functionally obsolete due to corrosion of the steel reinforcement. According to NACE International (2013) the annual cost of corrosion-related maintenance for highway bridges in the U.S. is estimated at $13.6 billion. Over the past couple of decades, fiber reinforced polymer (FRP) bars have been noted by researchers and engineers as a corrosion-resistant alternative for either conventional reinforcing steel or prestressing strands. High strength-to-weight ratio, corrosion resistance, ease in placement of the bars and accelerated implementation due to light weight are the special characteristics that make these bars an appealing alternative. Up to this end, extensive research has been conducted on the structural performance of FRP reinforced concrete beams and slabs; however, less attention has been paid to FRP reinforced concrete bridge girders in composite action with the bridge deck. Accounting for the effect of composite action between the bridge girder and deck can significantly impact the structural performance of the girder including the load and deformation capacities as well as the failure mode. Therefore, separate tests of the FRP concrete beams and slabs may not be sufficient to study the structural behavior and to provide design guidelines for engineers. This thesis presents the experimental and analytical investigations on structural performance of a full-scale AASHTO I-girder Type I, reinforced and prestressed with aramid fiber reinforced polymer (AFRP) bars, where the bridge girder is composite with the deck. The major objectives of this research were to develop a reliable prestressing anchorage system, examine the constructability of the full-scale specimen, study the load and deformation capacities, determine whether or not the design criteria per AASHTO LRFD were met, and improve the performance of the specimen by adjusting the prestressing layout. The specimen was constructed at a prestressing plant in San Marcos, Texas and tested at the High Bay Structural and Material Testing Laboratory on the campus of Texas A&M University. The cross-section of the bridge girder was composed of self-consolidating concrete with a total of 24 prestressed and 8 non-prestressed AFRP bars. The bridge deck consisted of a 203 mm (8 in.) conventional steel reinforced concrete slab. A flexure test was conducted to determine the moment-curvature relationship, flexure load capacity, and failure mode. The test was conducted as a simply supported, four point bending test in order to create a region of constant moment at the center of the beam. Two shear tests were conducted to determine the shear capacity, failure mode, maximum strain in the web, and moment-curvature relationship. The shear tests were conducted as a simply supported, three point bending test with varying load placement. The results of these tests were compared to a similar study which investigated the structural performance of a conventional steel reinforced AASHTO I-girder Type I with topping deck (Trejo et al. 2008). The specimen was also analyzed analytically to determine the effect on performance of varying the prestressing ratio of the separate layers in the bottom flange of the girder. The goal of this analysis was to determine an optimal prestressing layout to improve the performance at the ultimate state, while still satisfying serviceability limits. The prestressing ratio of the layers were varied from 0 to 50 percent in 5 percent increments to study the moment and curvature at both the cracking and ultimate states, along with the available compressive stress due to prestressing at the bottom of the girder. The results of this research confirms that the experimental specimen showed adequate strength and deformation capacities, satisfying the AASHTO LRFD design criteria. Additionally, the experimental specimen showed significantly greater cracking when compared to the conventional steel reinforced specimen, which is an early warning of impending failure. It was also determined that reducing the prestressing ratio of the AFRP bars in the lower layers improves the ductility of the specimen. The moment capacity can also be improved depending on the prestressing layout. However, reducing the prestressing ratio of the bottom layers causes the cracking moment and available compressive stress at the bottom of the girder to diminish. In order to compensate for this loss, the non-prestressed bars in the web can be prestressed. The optimal prestressing layout features the bottom three layers of the specimen prestressed to 35, 40, and 45 percent of their ultimate capacity, and two of the three layers of middle bars prestressed to 50 percent of their ultimate capacity.Item Cyclic Loading of Fiber-Containing Cement Sheaths in HPHT Conditions(2014-09-05) Johns, Andrew WesleyA Chandler 7600 Ultra HPHT Viscometer was setup to imitate well bore conditions of high pressure, high temperature wells, and the research objective was to investigate the reaction of Class H cement with 35% silica and 0.5% nylon fiber to cyclic loading. This experimental setup facilitated the cyclic loading of the cement sheath by maintaining a constant confining pressure while the casing pressure was cycled. The fatigue endurance limit was found for 1,000 psi and 2,000 psi cyclic pressure differentials for the Class H with added fiber and the results were compared with that of Class H cement without fiber. At 1,000 psi pressure differentials, the cement with fiber remained intact until 15 cycles, whereas the cement without fiber failed at 14 cycles. At 2,000 psi pressure differentials the cement without nylon failed at 14 cycles, whereas the cement without nylon fiber failed at 13 cycles. These results clearly show that the cement with 0.5% nylon maintained integrity for one cycle longer for both 1,000 and 2,000 psi differentials tests when compared to the same cement without nylon fiber. The cement with added nylon therefore exhibits an increased tolerance to cyclic loading.Item Cytoplasmic foci at the crossroads of artifactual science and biological function(2016-05) Zhao, Alice; Marcotte, Edward M.; Ellington, Andrew D; Zhang, Yan J; Appling, Dean R; Iyer, Vishwanath RDeciphering protein interaction and compartmentalization is crucial to understanding the molecular mechanisms that drive biological processes. Using various high throughput approaches, we have managed to score subcellular dynamic protein re-organization into supramolecular structures and map physical association networks to discover protein complexes on a proteome-wide level. However, the case by case studies of some of these novel structures and interactions reveal difficulties in interpreting their biological basis. This study offers insights into limits inherent in the molecular techniques used to investigate subcellular structures and protein interactions, describing a set of cautionary tales and critical analysis for deciphering cases of confounding data from orthogonal approaches. This study also offers a new experimental technique for high-throughput imaging assays with mammalian cell lines.Item Development of a Seed Cotton Fiber Quality Sensing System For Cotton Fiber Quality Mapping(2012-02-14) Schielack, Vincent PaulFor precision agriculture to work, an automated process to collect spatial-variability data within a field is necessary. Otherwise, data collection is prohibitively expensive and time consuming. Furthermore, to minimize measurement error due to harvesting method, data-collection processes involving normal cotton harvesting and ginning operations must be used. For the case of cotton, an automated prototype system using image processing to measure the micronaire value of cotton fiber during harvest was designed and built in the laboratory. This system was tested with two image-processing algorithms to identify and remove the effects of objects present in the images that were not cotton fiber, and then measure the reflectivity in three Near-Infrared (NIR) wavebands. Both algorithms yielded similar results when used on seed cotton samples. The reflectivity measurement after removing the effects of foreign matter had a strong relationship to standard micronaire measurements (R^2= 0.73 and 0.74 for the ratio-image and single-image algorithms, respectively) with a root mean squared error (RMSE) of 0.28 and 0.27, respectively. The ratio-image pixel classification method classified an average of 58% of the pixels in an image as "cotton", while the single-image method classified an average of 81% of the pixels in each image as cotton. These results do not show as strong a relationship between micronaire and NIR reflectivity of cotton samples as previous research done with very uniform lint cotton calibration samples. This is attributed to the higher content of foreign matter in seed cotton samples. With higher trash cotton and fiber that has not yet been cleaned, results obviously are not as good as when using calibration cotton samples. These results indicate the system can be adapted to perform in-situ measurement of cotton fiber quality, specifically micronaire, and enable harvesters to create quality maps of a field automatically to allow better crop management.Item Fiber optic sensing technology for measuring in-cylinder pressure in automotive engines(Texas A&M University, 2006-10-30) Bae, TaehanA new fiber optic sensing technology for measuring in-cylinder pressure in automotive engines was investigated. The optic sensing element consists of two mirrors in an in-line single mode fiber that are separated by some distance. To withstand the harsh conditions inside an engine, the Fiber Fabry-Perot Interferometer (FFPI) element was coated with gold and copper. The metal-protected fiber sensor was embedded into a small cut in the metal casing of the spark plug. At first, the sensing element was dipped in liquid gold and cured. Then the gold-coated fiber sensor was electroplated with copper. Finally, the metal-coated fiber sensor was embedded in the spark plug. The spark-plug-embedded FFPI sensor was monitored using a signal conditioning unit. Field tests were carried out in a 3-cylinder automotive engine with a piezoelectric pressure sensor as a reference transducer up to about 3500 rpm. The fiber optic sensor data generally matched those measured by the piezoelectric reference sensor. The use of a Vertical Cavity Surface Emitting Laser (VCSEL) diode as a light source in an FFPI optic sensor system was investigated. Reflected light from the FFPI sensing element was used to measure the optical path difference. With a 1550nm VCSEL as the light source in a 12mm cavity length Fiber Fabry-Perot Interferometer, spectral characteristics were examined to determine the proper combination of dc bias current, modulation current amplitude and modulation frequency. Single VCSEL operation and regular fringe patterns were achieved. The laser tuning was -41.2 GHz/mA and was determined from measurements of the shift in the spectral peak of the VCSEL diode output as a function of dc bias current. By testing the fringe movement as the FFPI sensor was heated, the temperature tuning coefficient for the optical length was determined to be 11 x 10-6 ????C. The results of these experiments indicate that the use of VCSEL diode as a light source for the FFPI sensor offers a viable alternative to the use of Distributed Feedback (DFB) laser diodes for monitoring at a lower bias current and modulating current amplitude.Item Molecular Basis of Quantitative Genetics Revealed by Cloning and Analysis of 474 Genes Controlling Fiber Length in Cotton(2014-07-11) Liu, Yun HuaCotton (Gossypium spp.) is a leading textile crop in the world, generating an annual economic benefit of over hundred billion USD. However, few genes controlling fiber quality and yield traits have been cloned and characterized to date. In this study, a large number of genes controlling the upper half mean length (UHML) of fibers were cloned using a newly-developed high-throughput gene and QTL cloning system and subjected to systems analysis. Furthermore, the molecular basis and regulation mechanisms of UHML were investigated using the cloned fiber length genes. A total of 474 GFL (Gossypium Fiber Length) genes were cloned. The effect of each GFL gene on UHML varied from 2.64% to 7.92%. Of 474 GFL genes, 88.6% decreased UHML when turned on or actively expressed in the developing fibers at the 10 days post-anthesis (10-dpa), whereas only 11.4% increased UHML. The GFL genes encode proteins and enzymes that are involved in a variety of biological processes and metabolic pathways. The 474 GFL genes interacted to form an interaction network in the 10-dpa fibers, which suggests that UHML is the consequence of interactions among the GFL genes. In addition, the evolution of fiber length was examined between diploid and tetraploid cottons using the GFL genes. The results showed that the variation of the GFL gene networks, including the number of genes and number of gene x gene interactions, also plays an important role in the variation of fiber length during polyploidization. Therefore, this study has, for the first time worldwide, cloned a large number of genes controlling UHML and deciphered the underlying molecular basis and regulation mechanisms, thus providing novel resources and knowledge for development of new toolkits for enhanced cotton fiber breeding. The UHML is determined not only by its controlling genes, GFLs, but also by their actions, action directions and interactions. Moreover, the results of this study have not only provided a first line of evidence that a quantitative trait is controlled by a large number of genes, but also added new molecular basis, thus forming the molecular mechanisms of quantitative genetics.Item Seismic retrofit of RC columns with FRP composites and anchorage system(2015-05) Psaros Andriopoulos, Apostolos; Jirsa, J. O. (James Otis); Hrynyk, TrevorResearch on the use of composite materials in structural applications started more than 30 years ago but still remains active. The challenges that accompany those applications are diverse and seem to increase as the variety of applications grows. There are several fiber-reinforced polymer (FRP) systems that have been introduced through the years for strengthening reinforced concrete (RC) structures. Those systems focus on strengthening of slabs, beams and columns. The present study pertains to seismic retrofit of rectangular RC columns. The typical FRP materials used in structural applications are introduced, as well as, how FRP materials become an integral part of the force-resisting system. In addition, analysis work pertaining to a series of strengthened RC columns was conducted and the results were compared to the experimental data. Moreover, deficiencies of typical material models were highlighted. Design guidelines are discussed and recommendations about current design practices are provided. Finally, research gaps and future research recommendations are identified.Item Seismic retrofit of RC columns with FRP composites and anchorage system(2015-05) Psaros Andriopoulos, Apostolos; Jirsa, J. O. (James Otis); Hrynyk, TrevorResearch on the use of composite materials in structural applications started more than 30 years ago but still remains active. The challenges that accompany those applications are diverse and seem to increase as the variety of applications grows. There are several fiber-reinforced polymer (FRP) systems that have been introduced through the years for strengthening reinforced concrete (RC) structures. Those systems focus on strengthening of slabs, beams and columns. The present study pertains to seismic retrofit of rectangular RC columns. The typical FRP materials used in structural applications are introduced, as well as, how FRP materials become an integral part of the force-resisting system. In addition, analysis work pertaining to a series of strengthened RC columns was conducted and the results were compared to the experimental data. Moreover, deficiencies of typical material models were highlighted. Design guidelines are discussed and recommendations about current design practices are provided. Finally, research gaps and future research recommendations are identified.Item Stochastic differential equation model for cotton fiber breakage(2007-05) Simsek, Hakan; Allen, Edward J.; Krifa, Mourad; Allen, Linda J. S.A stochastic differential equation (SDE) model is developed for fibers undergoing breakage during textile processing steps. The SDE model generalizes a classic deterministic model for fiber breakage. Furthermore, SDE model compares well with Monte Carlo computations for different fiber breakage phenomena. Also calculations with the SDE model exhibit a bimodal distribution in fiber lengths which is commonly seen in data.Item Tunable erbium-doped fiber ring laser using an intra-cavity filter(Texas A&M University, 2004-11-15) Fadel, Hicham JosephLinear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.Item Yield components of new germplasm(2007-05) Maulding, Gene; Albers, Dave; Hequet, Eric F.; Lyford, Conrad; Bednarz, Craig W.; Boman, Randal K.Cotton produces more fruiting sites than it will ever mature to harvest. Fiber lint yields vary from rain fed conditions of 150kg/ha to irrigated environments producing in excess of 2000kg/ha. The way in which cotton builds its yield has been researched and debated for years. There is a general agreement on the primary yield components but which of these components have the greatest impact is still debatable. The purpose of this study is to determine which specific variables contribute to cotton's overall lint yield and to determine their relative importance for different cultivars. Recent genetic improvements in cotton have led to a significant increase in the amount of lint produced by the newer cultivars. Six cultivars from Delta and Pine Land Company have been chosen for analysis. These cultivars are separated between the older cultivars and the newer cultivars taking their place in the market. This study found that there is not just one variable that contributes to cotton's final yield, but rather a combination of any of the variables that leads to an increase in yield. There is not just one set way for a cultivar to develop its yield; rather, each cultivar develops differently and adapts differently to fluctuations in the environment. Data indicated that the newer cultivars are producing longer fibers with lower micronaire values than their older counterparts.