A Computational Tool for the Design of Prestressed Cable Supported Structures

Examensarbete för masterexamen
Abdul Sater, Ahmad
Thor, Oskar
Abstract Cable supported structures are light-weight structures gaining their load-bearing capacity through the use of one or several cables in combination with other structural members such as struts, beams, and plates. Cables transfer loads in tension only and adapt their shape depending on the loading condition. The relationship between applied loads and deformations is therefore highly non-linear and consequently the geometrical shape of cables requires bespoke design approaches. Traditionally, architects and engineers have designed cable structures using physical models or with graphical methods. This has changed as advances in numerical analysis and computational engineering have been made over the recent century. Many software programs available today can be used for analysis. However, a key part of structural design requires the ability to "sketch" and "iterate", which is absent in many available packages. A computational design tool is developed with the aim to support the design in early design stages. After evaluating three existing numerical methods for large displacement structures, a solver with Green strain bar elements is implemented. The tool extends the open-source BHoM code library. Output data from the tool is benchmarked by comparing results with analytical and numerical models. By exposing the functionality of the tool to user-interfaces such as Grasshopper and Excel, users can explore alternative design proposals by changing a set of parameters. These parameters include the input geometry, initial prestress, section sizes and topology. Case-studies are used to highlight how this tool is used in Grasshopper. A set of design-objectives are defined and met by controlling a set of parameters, subsequently creating several designs proposals. For the studied cases, which display small strains and large displacements, the tool provides accurate results. Should a different analysis model be required, the tool is suited for modifications and extensions of its capabilities.
cable-supported structures, form-finding, prestress, geometrical stiffness, structural design., parametric design
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