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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
771

Pull-Out Strength of Fiberglass/Epoxy Composite RebarFabricated on a Three-Dimensional Braiding Machine

Machanzi, Tarisai 01 November 2017 (has links)
The objective of this research was to explore and demonstrate the production andperformance of fiber-reinforced polymer (FRP) rebar manufactured on a continuous threedimensionalbraiding machine for use as reinforcement in concrete structures. Differentconfigurations of fiberglass/epoxy composite cylindrical rebar rods were manufactured,embedded in concrete, and tested in axial tension to identify the relationships betweenmanufacturing parameters and tensile pull-out strength of the rebar. The strength of the bondbetween concrete and FRP rebar was investigated using the pull-out test detailed by ACI 440.3R-12. The rebar was a No. 4 size and produced by combining multiple tows of fiberglass/epoxyprepreg to form the core of cylindrical rods which were consolidated using spirally-woundaramid consolidation fibers. The manufactured rebar was cured at 121°C (250°F) as specified bythe material manufacturer, TCR Composites. Preliminary research performed on carbon/epoxyrebar guided the process of developing a test matrix based on multiple variables. Primaryvariables investigated included the nature of the consolidation fiber material (dry vs prepreg),and the use of sand coating as a secondary process. The rebar samples were cast in 200 mm x200 mm x 200 mm (8.0 in x 8.0 in x 8.0 in) concrete cubes to investigate bond strength. A testfixture was designed and fabricated for use on a universal tensile testing machine. Standard 12.7mm (0.5 in) diameter steel rebar and a commercially comparable fiberglass rebar were alsotested to provide baseline values. Measurements were collected at both the free and loaded endsof the rebar with free-end results being a more accurate presentation of rebar bond stress.Results showed that the bond strength was 6-13% higher for the free-end for rebarconsolidated with a dry tow compared to prepreg tow consolidated rebar. When sand was added,dry tow consolidated sand-coated samples showed higher bond stress in the range of 15-26% forthe free-end than samples consolidated with a dry tow but excluded sand coating. Samplesconsolidated with prepreg tow and coated with sand showed higher bond stress in the range of43-58% for the free-end compared to prepreg tow no-sand coating samples. Overall, for therebar manufactured on the 3-D braiding machine, the prepreg tow consolidated rebar samplesrecorded the highest bond strength values with a maximum average bond stress value of 15.2MPa (2.26 ksi). The dry tow sand consolidated rebar recorded a maximum average bond stressvalue of 11.4 MPa (1.65 ksi). The rebar purchased from American Fiberglass Rebar recorded amaximum average bond stress of 12.0 MPa (1.74 ksi) while the maximum average bond stress ofsteel rebar was 13.1 MPa (1.90 ksi). Results demonstrated that quality composite rebar can bemanufactured using the 3-D braiding machine and that consolidating the rebar with a prepregtow and coating the surface with sand resulted in a rebar which bonded well with concretecompared to commercialized FRP and steel rebar.
772

Pull-Out Strength of Fiberglass/Epoxy Composite RebarFabricated on a Three-Dimensional Braiding Machine

Machanzi, Tarisai 01 November 2017 (has links)
The objective of this research was to explore and demonstrate the production andperformance of fiber-reinforced polymer (FRP) rebar manufactured on a continuous threedimensionalbraiding machine for use as reinforcement in concrete structures. Differentconfigurations of fiberglass/epoxy composite cylindrical rebar rods were manufactured,embedded in concrete, and tested in axial tension to identify the relationships betweenmanufacturing parameters and tensile pull-out strength of the rebar. The strength of the bondbetween concrete and FRP rebar was investigated using the pull-out test detailed by ACI 440.3R-12. The rebar was a No. 4 size and produced by combining multiple tows of fiberglass/epoxyprepreg to form the core of cylindrical rods which were consolidated using spirally-woundaramid consolidation fibers. The manufactured rebar was cured at 121C (250F) as specified bythe material manufacturer, TCR Composites. Preliminary research performed on carbon/epoxyrebar guided the process of developing a test matrix based on multiple variables. Primaryvariables investigated included the nature of the consolidation fiber material (dry vs prepreg),and the use of sand coating as a secondary process. The rebar samples were cast in 200 mm x200 mm x 200 mm (8.0 in x 8.0 in x 8.0 in) concrete cubes to investigate bond strength. A testfixture was designed and fabricated for use on a universal tensile testing machine. Standard 12.7mm (0.5 in) diameter steel rebar and a commercially comparable fiberglass rebar were alsotested to provide baseline values. Measurements were collected at both the free and loaded endsof the rebar with free-end results being a more accurate presentation of rebar bond stress.Results showed that the bond strength was 6-13% higher for the free-end for rebarconsolidated with a dry tow compared to prepreg tow consolidated rebar. When sand was added,dry tow consolidated sand-coated samples showed higher bond stress in the range of 15-26% forthe free-end than samples consolidated with a dry tow but excluded sand coating. Samplesconsolidated with prepreg tow and coated with sand showed higher bond stress in the range of43-58% for the free-end compared to prepreg tow no-sand coating samples. Overall, for therebar manufactured on the 3-D braiding machine, the prepreg tow consolidated rebar samplesrecorded the highest bond strength values with a maximum average bond stress value of 15.2MPa (2.26 ksi). The dry tow sand consolidated rebar recorded a maximum average bond stressvalue of 11.4 MPa (1.65 ksi). The rebar purchased from American Fiberglass Rebar recorded amaximum average bond stress of 12.0 MPa (1.74 ksi) while the maximum average bond stress ofsteel rebar was 13.1 MPa (1.90 ksi). Results demonstrated that quality composite rebar can bemanufactured using the 3-D braiding machine and that consolidating the rebar with a prepregtow and coating the surface with sand resulted in a rebar which bonded well with concretecompared to commercialized FRP and steel rebar.
773

Field observations and laboratory studies on growth and tillering in seedlings of oryzopsis hymenoides as affected by selected environmental factors of the sand dunes of Lynndyl, Utah

Smigelski, Leopold B. 01 August 1968 (has links)
Seedlings of Indian rice grass Oryzopsis hvmenoides (Roem. & Shult.) Ricker. were studied to determine the effect of soil moisture, photoperiod, depth of burial of germinated grains, temperature, and the rate of soil accumulation on seedling growth and tillering. The study was performed in two phases: Field observations and laboratory studies. Field observations were made on a system of sand dunes located northwest of Lynndyl, Utah. General observations were made from January, 1966 to May, 1968.
774

The Origin Of The Lion's Head Peninsula Beach

Davidson, Ian Ritchie 04 1900 (has links)
<p> The beach deposits at the head of the Lion's Head Peninsula are described and categorized according to the type, size and morphology of the rocks making up the deposit and their origins. This categorization emerges as a pattern of four zones along the l ength of the beach. </p> <p> The points at each end of the beach, which used to be in a much more defined bay, have been glacially eroded by re-entrants and undercut by postglacial lakes. Shales and dolomite from the escarpment make up this zone's deposits. </p> <p> Zone two is a dolomite cobble beach supplied by the escarpment's erosion from a blockaded late-glacial ice margin and the undercutting of postglacial lakes. </p> <p> Zone three is a mixture of the dolomite from the escarpment, lacustrine sand deposits, and glacial erratics. </p> <p> Zone four is made up of a distinct band of erratics deposited by the ice of the Georgian Bay lobe of the Late Wisconsin Glaciation. The Lion's Head promontory stood resistant to the flow of ice and caused it to deposit these large erratics which are still visible today. </p> / Thesis / Bachelor of Arts (BA)
775

Cement stabilization of poorly graded sand

Sisung, Lana Grayson Brown 08 December 2023 (has links) (PDF)
Stabilization of poorly graded sand in full-scale applications is challenging. This thesis evaluated cement-stabilized sand and had two objectives: (1) evaluation of stabilized material using the PM device to quantify engineering properties for future comparison to alterative materials and to investigate the effectiveness of the device with sand and (2) investigation of the merits of alternative application of cement to sand to benchmark against other topically applied materials. The PM device was successfully used to recommend 10% cement for field studies with one sand, successfully allowed data collection in laboratory and field applications, and its potential in sand seems promising though more overarching conclusions on characterization of sand using the PM device are withheld for subsequent efforts. Topical application methods developed in this thesis were able to percolate cement into sand and produce an average estimated unconfined compressive strength of 245 psi measured on cores that were 2.5 inches thick.
776

Migrating Sandscapes: From the Microparticle to the Architecture

Albunni, Lamia 25 May 2023 (has links)
No description available.
777

The succession of vegetation on a southern Utah sand dune

Castle, Elias S. 01 August 1954 (has links)
The sand dunes lying ten miles northwest of Kanab in Kane County, Utah, support a sparse plant cover with four species dominating the vegetation: Psoralea stenostachys, Sophora stenophylla, Oryzopsis hymenoides, and Wyethia scabra var. attenuata. Of these Psoralea and Wyethia are endemic to the dunes or to a limited area which includes the dunes. The pineer species gain a start in the valleys between dunes and occupy the area only until sand covers them or until sand is blown away from their roots. Stabilization of the soils is not permanently in the interdune valleys and the dunes continue to wander. The low fertility of the soils, the low moisture content, the extremes of temperature, light, and other environmental factors limits the number of individual plants which can occupy the dunes. The region will continue to have actively moving dunes until major climatic changes occur permittimg a denser plant cover which would tend to stabilize the sands.
778

An Investigation of Source Water Feeding Buck Creek, Great Sand Dunes National Monument and Preserve

Neu, Roene Ellen Medellia January 2005 (has links)
No description available.
779

DEMYSTIFYING HOUSE OF SAND AND FOG THROUGH POSTCOLONIAL AND FEMINIST LENSES

Ark, Darcy Lynne 27 March 2007 (has links)
No description available.
780

A Path Toward Equality in George Sand's <i> Horace</i>, <i> Mauprat</i>, and “Lavinia”

Miller, Katarina 19 July 2012 (has links)
No description available.

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