Theses and Dissertations

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

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    Analysis of the Mechanical Behavior of Explosive Spalling Resistant Ultra High Performance Concrete (UHPC) Beam and Column Members Under Combined Structural and Fire Loading
    (University of Alabama Libraries, 2024) Satioglu, Azize Ceren; Bhardwaj, Saahastaranshu R.
    Ultra High Performance Concrete (UHPC) stands out as a robust and enduring material, demonstrating superior compressive and tensile strength in comparison to both ordinary concrete and high strength concrete. Despite its exceptional strength and durability, UHPC presents a potential explosive spalling issue when subjected to fire loading, necessitating precautionary measures. Existing research on the development and use of fire resistant UHPC for structural elements is limited. This dissertation delves into the critical aspect of the behavior of UHPC under fire loading conditions by presenting a detailed review of the selected work conducted on the subject to date. The primary objective of this dissertation is to comprehend the explosive spalling resistant UHPC beam and column behavior under combined structural and fire loading by the aid of simulation, benchmarking and parametric 3D nonlinear finite element analysis. The study involves a comprehensive comparison of various material models and incorporating considerations for creep, transient strains, and material failures specific to UHPC and steel. The benchmarked FE models are used to conduct detailed parametric studies aimed at comprehensively examining the behavior of beams and columns made of non-spalling UHPC under both fire and structural loading conditions. The literature review reveals the importance of steel and polypropylene (PP) hybrid usage on the explosive spalling resistance. As the result of the parametric studies, it has been observed that, load percentage, load eccentricity, size of the cross section, number of fire surfaces, length, longitudinal reinforcement ratio and support conditions affect the behavior significantly. On the other hand, the behavior of the explosive spalling resistant UHPC beam and column under combined structural and fire loading was affected less significantly by the change in the stirrup ratio, UHPC and steel strengths, cover thickness and geometric imperfection parameters. In future work, the outcomes of these analyses will be leveraged to formulate capacity equations for elevated temperatures and determine fire resistance ratings for non-spalling UHPC beams subjected to combined structural and fire loading. This is particularly relevant for the prospective application of UHPC in fields where endurance and high strengths are necessary for elements when they are exposed to high temperatures.