"The Future of Us" – Resolving gridshell buckling risks
Singapore's 'Future of Us' exhibition captured the imagination of the public and inspired more than 400,000 individuals to record their hopes, dreams and promises.
The exhibition was spread across four domes linked by a large-span shell structure, engineered by Singaporean firm Passage Projects. Passage Projects worked closely with Architects at the Singapore University of Technology and Design Advanced Architecture Laboratory to design the gridshell's metal lattice structure to generate a stunning play of light and shade cast by the lattice – creating the illusion of walking through a forest. The engineers were faced with challenges due to the complexity of the design but were able to resolve the challenges using Oasys GSA analysis.
The steel structure, spanning approximately 50m and rising to 16m, supports 11,000 perforated aluminium panels. The structure consists of primary arches and a secondary bracing structure. Most of the connections are bolted, allowing for a fast construction cycle of just under 5 weeks.
The global analysis of the steel structure was carried out using Oasys GSA. The structure was first modelled on Rhino and imported into the GSA software seamlessly using the AutoCAD DWG/DSF import tool. View the analysis model in GSA plan view in the image slider above.
Instabilities investigations
A modal buckling analysis was carried out under ULS loadings. In some locations, arch buckling modes were found to have a buckling factor smaller than 3. The arches at these locations are very flat and are subject to high compression forces. The GSA analysis helped to identify the arches requiring additional stiffness. It was decided to stiffen these flat areas of the gridshell by fixing all the primary purlins to the affected arches. This increased the buckling factor from 3 to 8.
Buckling of flat arches with a buckling factor smaller than 3
Plan view of the analysis model – All primary purlins are pinned to the arches, except at the flat area where they are fixed
Instabilities and Geometrical imperfections.
Three global buckling modes remained with a buckling factor lower than 10. To resolve this issue, a geometrically non-linear elastic analysis was done. Global imperfections were included in the model and local imperfections taken into account through members checks.
Engineers were able easily to include these global imperfections in their calculations because GSA has built-in tools to create a new model from deformed geometry. This used the deformed shape of the first global buckling mode, with the maximum amplitude of the global imperfection limited to 30mm. A non-linear analysis was then carried out on this new model and the results used to check the structural members.
Buckling mode – buckling of arches
Axial force – ULS Moment – ULS
The Future of Us exhibition, Singapore
Engineers: Passage Projects / Sh Ng
Architects: Advance Architecture Laboratory, SUTD
"The project reinvents the experience of a tropical space by providing a comfortable, unique, multi-sensorial and climatically appropriate experience to be enjoyed by everyone."
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