Doctoral Degrees (Civil Engineering)

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Browsing Doctoral Degrees (Civil Engineering) by Subject "Bayesian calibration"

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    Structural reliability of ultra-high performance fibre reinforced concrete structures
    (Stellenbosch : Stellenbosch University, 2022-12) Simwanda, Lenganji Shadrek; De Koker, Nico; Viljoen, Celeste; Babafemi, Adewumi John; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: The current lack of established guidelines for ultra high-performance fibre reinforced concrete (UHPFRC) structures has resulted in their design and construction being based on recommendations adapted from provisions for either conventional reinforced concrete or steel fiber reinforced concrete. Despite these approaches being associated with a fair amount of uncertainty with respect to the performance of the material, the margin of structural safety of UHPFRC structures designed using these guidelines has not been extensively probed in a probabilistic context. Structural reliability provides the most objective and consistent measure of structural safety and allows, in a probabilistic context, comparison of alternative design solutions. As such, it forms a key part of the standardisation of modern structural codes of practice through the prescription of partial safety factors calibrated to conform to minimum levels of safety and is used in probabilistic performance-based design philosophies to target the relevant levels of safety (or performance) directly by explicitly computing the probability of failure. Therefore, to stochastically quantify the level of structural safety in UHPFRC structures, and to take steps towards standardisation for their efficient design, this dissertation presents five studies associated with the development and calibration of methodologies for considering the structural reliability of UHPFRC structures. The first and second studies consider the reliability-based design of UHPFRC beams under the limit states of flexure and shear, respectively. Based on the model uncertainty characterised in these studies, global resistance factors for flexural and shear resistance models of UHPFRC beams are calibrated in the third study. The reliability of existing reinforced concrete beams strengthened with UHPFRC tensile layers is considered in the fourth study. Lastly, a work on Bayesian calibration of temperature-dependent thermal physical properties of UHPFRC and structural reliability of UHPFRC beams under the fire limit state of the load-bearing function is presented.