Browsing by Author "Elvin, Alex"

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    A Comparative Study of the Efficiencies of Vertical Bracing Practices
    (University of the Witwatersrand, Johannesburg, 2023-11) Saunders, Shawn Wayne Valintino; Elvin, Alex
    The efficiencies of cross sections and configurations applied to vertical bracing are investigated by evaluating reference configurations (RCs), composed of cross braced circular hollow section (CHS) members, against comparative configurations (CCs), consisting of cross-braced Angle members, and single-CHS members. The metrics used to evaluate efficiencies were mass, raw materials costs, and fabrication and erection costs. CCs were found to be more efficient than RCs for most analysed cases, metric and configuration dependent. The following results were found: i. Mass metric a. Crossed-Angle more efficient in 79% of analysed cases. b. Single CHS more efficient in 87% of analysed cases. ii. Raw materials costs metric a. Crossed-Angle more efficient in 92% of analysed cases b. Single CHS more efficient in 88% of analysed cases iii. Fabrication and erection costs metric a. Crossed-Angle more efficient in 90.4% of analysed cases b. Single CHS more efficient in 88.5% of analysed cases Inversions of the efficiency parameter findings, with RCs more efficient than CCs, were observed when: i. RC CHS member slenderness ratios were less than 80-90. ii. CC design loads were greater than 225 kN, 1200 kN and 1500 kN for mass, raw materials and total cost efficiency metrics, respectively
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    Optimizing Structures with Semi‑Rigid Connections Using the Principle of Virtual Work
    (Springer, 2018-04) Elvin, Alex; Strydom, Johnnie
    In this paper, the virtual work optimization method (VWOM) has been generalised to consider structures with semi-rigid connections. The VWOM is an automated method that minimizes the mass of a structure with a given geometry, multiple deflection criteria, and load cases while adhering to design code requirements. In the optimization process, members are selected from a discrete database to meet all strength and stiffness criteria. Connections are modelled using rotational springs, allowing some moment transfer. The rotational stiffness of each connection can be varied from rigid to pinned. The example of a pitched roof frame is used to explain the method. Two case studies are considered: (i) (i) a three-storey two-bay and (ii) a four-storey three-bay office building. The VWOM produced results up to 26.7% lighter than results in the literature. Furthermore, the structures were optimized for a range of rotational stifness, where all connections in the structure were assumed to have the same rotational stiffness. Characteristic jumps in the optimized mass versus rotational stiffness were observed.