Client: City of Joensuu
Architects: Pro-Ark Oy Marjatta Hara-Pietilä, Pentti Värälä
Engineers: Finnmap Consulting Oy
Timber suppliers: Finnforest Oy, Late-Rakenteet Oy
Contractors: YIT Rakennus Oy

The City of Joensuu, in Karelia, eastern Finland, invited tenders for a new multisports arena in December 2001. The arena was to cater for mixed sporting events, physical recreation, conferences, concerts and other public events, all to a specified budget. The winning proposal was a timber structure, particularly appropriate in this area rich in forest products industries, close to large areas of sustainably managed forests.

Multipurpose, flexible usage was an important aspect of the design brief. A three-storey entry area includes offices, locker and changing rooms, and access to the stands. The main hall is an oval timber dome, approximately 150m long, with a clear central height of 24m, created from a series of latticed arches up to 110m across. Large enough to accommodate 7,000 spectators, it also encompasses an enclosed soccer pitch, athletics track and areas for other track and field events, as well as various ball games. A grandstand area for 2,000 spectators can be adapted to suit different events or removed completely.

The timber engineering aspects of the project are impressive, with the repetitive use of 28 latticed half-arch frames making good use of prefabricated manufacture and allowing an orderly erection process.

The central crown of the roof, receiving the thrust of the half-arches, is a boatshaped glazed spaceframe, which introduces natural light over the main arena, enhanced by special reflective sails. The arches have glulam main chords, with LVL (Laminated Veneer Lumber) latticed web members and purlins.

Inconspicuous dowel-type fasteners are used to connect the majority of the web-to-chord nodes and the roof lantern structure. Some of the main arch connections, including the base-to-foundation details, use true pinned connections with forged and welded steelwork. This is attached to the timberwork with flitched-in dowel connections.

Approximately 1,300m3 of glulam and LVL was incorporated in the main structure, using 39,000 dowel-type fasteners, together with about 150 tonnes of steelwork.

The construction and erection sequence involved the completion of the foundations and the arch bases as the initial stage. Next, the prefabricated 55m long x 10m wide crown unit, made in Finland mainly from LVL, was assembled on the ground and lifted in place using tower cranes. The half-arches were then partially assembled at a low level, including the addition of thermal insulation, waterproofing membranes, and HVAC equipment. Once connected to their reinforced concrete bases, the frames were raised in opposing pairs and locked into final position on the skylight structure.

The arena, covering 14,483m2, was opened according to plan in 2004 and is thought to be the largest timber structure in Finland. It won the Finnish Association of Civil Engineers Award, 2004.