Theses and Dissertations

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Browsing Theses and Dissertations by Author "Aaleti, Sriram R"

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    Application of Ultra-High Performance Concrete in Prefabricated Bridge Element Connections for Accelerated Bridge Construction
    (University of Alabama Libraries, 2023) Bridi Valentim, Daniel; Aaleti, Sriram R; Kreger, Michael E
    A relatively new type of beam falling under the accelerated bridge construction (ABC) umbrella, the Northeast Extreme Tee (NEXT) D beam, was designed by the PCI Northeast Bridge Technical Committee, with connection details that substitute traditional welded ties joining butted-beam systems, such as bulb-tee girders and double-tee beams. Grout has traditionally been used in joints between prefabricated bridge elements and systems (PBES). This material, however, has resulted in issues with shear key cracking reported by the Federal Highway Administration. An alternative cementitious material, ultra-high performance concrete (UHPC), has been used as a great solution for connections between PBES in ABC. This material exhibits superior properties such as compressive, tensile, and bond strength, durability, and long-term stability when compared to conventional connection materials. Three main studies are presented herein. The first study presents a tensile strength evaluation of 54 UHPC specimens by comparing the direct tension (DT), four-point bending, and double-edge wedge-splitting (DEWS) test methods. No statistically significant difference was found between the peak tensile strengths obtained from DT and DEWS specimens. DEWS specimens are tested using a compression-testing machine, and can be cored and finished from existing UHPC members. The second study evaluates the bond-slip behavior of UHPC and untensioned prestressing strands. The variables studied in the 54 tested pull-out specimens include clear cover, embedment length, and strand diameter (dPT). It was observed that specimens that experienced strand failure had an embedment length of at least 24×dPT or clear cover distance of 2.17×dPT. The third study investigates the behavior of NEXT D beams under fatigue loading. Four double-tee and four slab specimens were subjected to 1 million cycles under AASHTO standard wheel truck loads. Moreover, finite element analyses (FEAs) were performed, effectively simulating the tested specimens, and a 60-ft. long bridge model was created to simulate a constructed bridge in Mobile County, Alabama. It was observed that an 8-in. (203-mm) wide UHPC joint with a single reinforcement layer containing straight #5 bars, an 8-in. (203-mm) embedment length, and spaced every 6 in. (152 mm) had satisfactory performance according to results from experimental testing and FEAs.
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    Improving Engineering Design and Structural Performance Through the Effective Characterization of High-Performance Materials in Geotechnical Transportation Engineering
    (University of Alabama Libraries, 2022) Skelton, Eleanor Huggins; Amirkhanian, Armen; University of Alabama Tuscaloosa
    Innovations in engineering materials are useful in the construction of sustainable and resilient infrastructure for our rapidly changing world, but the effective use of alternative engineering materials often requires changes to engineering design, construction, and testing techniques. This research considers a range of materials that may be used in geotechnical transportation engineering applications: Cement Modified Recycled Base (CMRB), Cement Stabilized Aggregate Base (CSAB), All-Weather Fill (AWF), and Ultra-High-Performance Concrete (UHPC) H-piles. These materials have been selected as research subjects because they 1) make use of recycled materials and/or offer high-performance characteristics and 2) present potential challenges to traditional testing, modeling, design, and/or performance verification methods. CMRB and CSAB offer improved subgrade performance and CMRB makes use of RAP, but the methodology for modeling the resilient modulus of cement-modified materials in Mechanistic-Empirical Pavement Design is not currently well understood. AWF is a proposed trade name that refers to crushed stone materials that are produced by aggregate manufacturers, but which do not meet the specifications for acceptance as crushed stone fill, base, subbase, or concrete/asphalt aggregates. Such materials are expected to offer significant reductions in construction weather delays by better resisting traffic when wet compared to conventional soil fills, but it is necessary to quantify, through trafficability and drying modeling, the improved trafficability and reduction in construction delays (and the associated cost savings) that AWF can offer. Finally, H-shaped UHPC piles that can be cast with steel end caps that can be spliced can arguably be used in any application where steel H-piles can be used, and UHPC offer many performance and durability benefits. However, the steel splicing plates, steel fibers, or other characteristics of the UHPC H-piles will potentially affect the results of conventional wave-based pile integrity and capacity tests, including the commonly used Pile Driving Analyzer (PDA). This research focuses on the effects of longitudinal material heterogeneity, UHPC material properties, and section shape on dynamic field testing of UHPC piles and how this may affect wave-based field evaluations in engineering practice. Overall, the research presented in this report will inform the use of selected high-performance materials in civil engineering practice.