Portalen

The Portalen pavilion is a double-layered deployable timber gridshell in the tradition of Frei Otto and his team, and it serves as meeting space and venue for the community centry of Hageby in the city of Norrköping, Sweden. The shell is designed as a simple flat mat of timber laths, which can bent into its three-dimensional form. Once positioned onto the glued laminated timber arches, the shell is braced by cables and covered by polycarbonate sheets.

A group of architects and engineers who had recently immigrated to Sweden wished to create a community centre for Portalen in Hageby, Norrköping. Portalen is a centre for labour-market integration and a place to make new contacts and find employment. The project was then formalized under the national programme “Art is happening”, conducted by the Statens Konstråd (Public Art Agency), collaborating with Norrköpings Konstmuseum and Portalen. In the Summer of 2016, in collaboration with Spanish architects Map13 Barcelona, they used experimental, vaulted brick work, to explore the potential nature of this meeting place. As a first step towards a community centre, the intent was to build a pavilion, initially envisioned as a large masonry vault.

Summum Engineering along with Edyta Augustynowicz were then invited to assist with parametric modelling and structural engineering. Due to poor soil conditions, the pavilion was then re-imagined as a more modestly sized timber structure, and the decision was made to build a deployable gridshell. We proceeded with the structural design on that basis.

Design

The gridshell was parametrically modelled by first generating a surface that met architectural and constructional constraints. A grid was mapped onto this surface using the compass method in order to create a so-called Chebyshev net – a network in which each edge has the same length – to guarantee that the curved form could be built using a square, flat mat of timber laths. This discrete network was then altered using form finding to improve its structural and constructional performance, before being analyzed.

Engineering

The structural model included various aspects including the layered timber with scissor hinges and joint slip of the timber connections, sliding cables with prestress, higher-order geometric nonlinearity as well as material properties according to Eurocode (a simpler analysis without many of these features would lead to a 30% increase in material use). The analysis was approached in two different ways: first, similar to seminal structures in the UK, such as the Weald & Downland Gridshell by viewing the actively bent gridshell as a set of curved glulam beams (advice was sought from the original engineers from Buro Happold and builders from Green Oak Carpentry), and second, by taking the residual bending stresses from deployment into account in combination with material creep. The gridshell was evaluated with respect to deflection, material strength and global buckling; the latter by comparison with buckling factors achieved for Frei Otto’s Multihalle gridshell in Mannheim, Germany.

Structure

The structure consists of two layers of timber laths in two directions, forming a grid. The grid was designed to be built as a flat mat on the ground, and then lifted to form a three-dimensional curved surface that works as an efficient shell structure. The grid is supported by four curving edges meeting at the four corners. These open arches made of glued laminated timber. Instead of deploying the grid, the contractor opted to build the grid lath by lath, using the edges and a temporary support as guidework. After bracing the grid with steel cables, the entire shell was covered by polycarbonate sheets. This cladding allows for light to pass through, transforming the perception of the interior and the exterior space.

The Portalen Pavilion officially opened on Friday, September 25th, 2050. This final art piece now serves as a permanent and public pavilion for Sweden’s newest citizens making their way to Portalen and finding their place in their new home country.

Project owner
Hyresbostäder

Project developer
Joanna Zawieja, Lena From| Public Art Agency Sweden (Statens Konstråd)

Project architect and client
Map13 Barcelona

Design and modelling team
Marta Domènech Rodríguez, David López López, Mariana Palumbo Fernández, Teresa del Pozo Lérida, Delfina Capiglioni, Antonio (Toni) Planas Portas, Alejandro Caballero | Map13 Barcelona
Diederik Veenendaal, Sjef Brands | Summum Engineering
Edyta Augustynowicz

Parametric modelling
Edyta Augustynowicz
Diederik Veenendaal | Summum Engineering

Project support
Marcus Abrahamsson | Nyrens

Structural engineering
Diederik Veenendaal | Summum Engineering (final design)
Andreas Alpkvist, Joacim Vilén | Tyrens (geotechnical design)
Limträteknik i Falun (construction design)

Contractor
David Ramberg | Dala Massivträ (project management)
JR Dala Bygg (assembly)

Suppliers
Sveden Trä (timber laths)
Hasslacher Norica Timber (glulam arches)
Swans Mekaniska (steel connections)
Carl Stahl (steel wire bracing)
GOP (polycarbonate cladding)
SFS Intec (connections)
Rothoblaas (connections)
Wurth (connections)
Swerbolt (connections)
Ahlsell (connections)

Construction consultant
Steve Corbett, Andrew Holloway | Green Oak Carpentry