Browsing by Author "Van Rooyen, G. C."

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    Critical normal traffic loading for flexure of skew bridges according to TMH7
    (South African Institution of Civil Engineering, 2013-10) Malan, Andreas D.; Van Rooyen, G. C.
    Different types of loading due to traffic may act on bridges. The focus of this paper is on normal traffic loading according to the South African specification TMH7 (Committee of State Road Authorities 1988). TMH7 represents the code of practice for the design of highway bridges and culverts in South Africa. The aim of the paper is to provide additional insight into the effect of normal traffic loading patterns on the flexural analysis of skew bridges. This is necessary since TMH7 does not explicitly specify application patterns for normal traffic loading. Only the intensity of normal traffic loading is specified and it should be applied to yield the most adverse effects. In this paper a set of so-called “standard application patterns” are investigated and compared with the application patterns that yield the most adverse effects. The patterns are compared for flexural effects in selected design regions of the bridge deck. Numerical experiments were performed and are presented for a typical single-span bridge deck. The results of the numerical experiments are compared as the angle of skew of the bridge deck increases.
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    Sewer network design : heuristic algorithm for hydraulic optimisation
    (South African Institution of Civil Engineering, 2017-09) De Villiers, N.; Van Rooyen, G. C.; Middendorf, M.
    ENGLISH ABSTRACT: For a given sewer network layout and choice of pipe material, the total installed cost of the network is determined mainly by the pipe diameters and slopes. Hydraulic design optimisation is the task of determining suitable pipe diameters and slopes so as to minimise the installed cost of the network. This is a complex problem for which numerous solution approaches have been proposed. Recently the use of metaheuristic algorithms, like Ant Colony Optimisation (ACO) for example, has gained popularity, and they perform well for a given static layout. However, their computational complexity precludes their use in simultaneous layout and hydraulic optimisation, where a complete hydraulic optimisation has to be performed for each layout. This paper proposes a computationally efficient method for near optimal hydraulic design of a gravity sewer network. It makes use of required minimum slope information to heuristically determine optimal pipe sizes and slopes. The method is used to solve two benchmark problems and is shown to obtain good solutions while being computationally extremely efficient. Therefore it is ideally suited to be used in combination with a metaheuristic algorithm aimed at optimising the network layout.
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    Sewer network design layout optimisation using ant colony algorithms
    (South African Institution of Civil Engineering, 2018) De Villiers, Nico-Ben; Van Rooyen, G. C.; Middendorf, Martin
    The optimal design of sewer networks typically comprises two sub-problems. The first is to determine an optimal layout of the network elements, and the second to optimally design the network components. In this article the focus is on the optimisation of gravity sewer network layouts, which requires simultaneous optimisation of hydraulic design. The layout is optimised using ant colony algorithms with four proposed node and edge-based selection strategies, while a heuristic optimisation algorithm is used for the hydraulic optimisation. The resulting simultaneous optimisation algorithm is shown to perform very well. The selection strategies are shown to be effective, but no clear best strategy is identified, as the performance of the layout algorithms is shown to depend heavily on characteristics of the network under consideration. However, some strategies are shown to perform inconsistently and worse than others on average.