Browsing by Author "Walls, Richard Shaun"

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    A beam finite element for the analysis of structures in fire
    (Stellenbosch : Stellenbosch University, 2016-12) Walls, Richard Shaun; Viljoen, Celeste; De Clercq, Hennie; Stellenbosch University. Faculty Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: All building structures require a specified fire resistance rating and numerous procedures have been produced for ensuring this. In engineering practice designers can generally not perform detailed structural fire designs on buildings due to the high computational modelling requirements of most modern structures, and so they typically resort to conservative prescriptive methods instead. Hence, design engineer orientated methods are required to improve fire safety while providing more economical buildings. The goal of this dissertation is to provide a simple, but technically accurate, model for the analysis of structures in fire, including composite structures, which considers buildings as skeletal frames. To achieve this end a beam finite element has been developed that has a moving, eccentric neutral axis that accounts for material properties that change as structures heat up. A composite bending stiffness, axial stiffness and resultant thermal forces are calculated for a generic cross-section. Material and geometric nonlinearity is considered. The properties of any number of materials (e.g. a steel beam, concrete slab and reinforcing steel) are represented by single beam properties. These calculated beam properties can be included in either commercially available, but simple, finite element software or advanced finite element modelling tools. The only assumption required is that Euler-Bernoulli behaviour, where plane sections remain plane, must hold. A methodology for including rebar tension stiffening at elevated temperatures has been included based on modifying an ambient temperature model. A series of numerical case studies are presented, comparing the results of the proposed beam formulation against finite element models using shell elements. Results between these models (which includes deflections, stresses, strains and neutral axis positions) typically differ by 0-5% when Euler-Bernoulli assumptions hold. Furthermore, case studies and experimental results from real fire tests in the literature were also analysed by the proposed formulation coupled with relatively simple finite element software. The deflections of structures in fire predicted by the proposed model are well within acceptable tolerances for fire engineering systems, and typically comparable to more complex models in the literature. The model developed has been used to investigate eleven different beams consisting of steel beams, concrete slabs and composite steel-concrete beams, along with conducting a series of parametric studies. With further research and the inclusion of three-dimensional behaviour the method could become a valuable tool for the analysis of structures in fire.
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    Fire risk reduction on the margins of an urbanizing world
    (Emerald, 2020-10) Rush, David; Bankoff, Greg; Cooper-Knock, Sarah-Jane; Gibson, Lesley; Hirst, Laura; Jordan, Steve; Spinardi, Graham; Twigg, John; Walls, Richard Shaun
    Purpose: Globally, over 95% of fire related deaths and injuries occur in low- and middle-income countries. Within informal settlements, the risk of fire resulting in injury or death is particularly high. This paper examines fire risks in informal settlements in New Delhi and Cape Town, and tented informal settlements in Lebanon. Design/methodology/approach: Our analysis draws on primary sources, secondary literature, statistical data and qualitative interviews. Findings: The distribution of fire risk across urban societies is a fundamentally political issue. Residential fire risk can be tackled by accessible, affordable, safety-compliant housing. That said, important interim measures can be taken to mitigate fire risk. Some of the risks requiring attention are similar across our case studies, driven by high population densities; flammable housing materials; unreliable or inaccessible access to safe power sources; and – in the case of Cape Town and New Delhi particularly – the inability of fire services to reach sites of fire. However, these common risks are embedded in distinct social, economic and political contexts that must be placed at the center of any intervention. Interventions must also be aware that the risk of fire is not spread evenly within informal settlements, intersecting as it does with factors like gender, age, health and disability. Originality/value: Informal settlement fires have been under-studied to date. The studies that do exist tend to operate within disciplinary silos. This paper represents an important interdisciplinary approach to fire within informal settlements, which grounds technical data, modeling and experiments in political, social and economic realities.