Browsing by Author "Muigai, Rachel Njeri"

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    A framework towards the design of more sustainable concrete structures
    (2014) Muigai, Rachel Njeri; Alexander, Mark Gavin
    The main contribution of this study is the development of a novel framework for the design of reinforced concrete (RC) structures which aims at ensuring that future RC structures have the lowest possible carbon footprint, energy use and impact on the environment. The key focus of the study is on structural design where there is a lack of grasp of materials aspects, and environmental aspects of construction. In the proposed framework, a set of quantifiable design parameters and variables (binder type, concrete grade, diffusivity, concrete cover depth, area of steel in the structural component) are selected with respect to a set of performance measures which cover the functionality and availability of the structure to the user during its service life. The outputs generated from the framework are optimised material types and properties which not only meet the design performance requirements but also lead to minimised life-cycle environmental impacts. Two case studies are used to demonstrate the proposed design methodology. These include a reinforced concrete frame building and a post-tensioned box girder. The application of the framework for design in the material specifications showed a reduced volume of materials in construction compared to the current materials and structures design practice.
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    Probabilistic modelling for durability design of reinforced concrete structures
    (2008) Muigai, Rachel Njeri; Moyo, Pilate
    The purpose of this study was to create a framework for the development of a probabilistic model for durability design of reinforced concrete (RC) structures in South African marine conditions. Durability design of RC structures is mainly concerned with ensuring the ability of the concrete to resist the penetration of aggressive agents during the concrete‘s intended service life. RC structures in the marine environment may be attacked by aggressive chloride ions which penetrate concrete mainly through the diffusion mechanism. The chloride ions accumulate at the steel level and, upon reaching a critical concentration, cause corrosion to initiate which if not intercepted leads to the eventual deterioration of the entire structure.