Paul Van Ratingen
Johnson Pilton Walker, Sydney
Mjøstårnet is an 85-meter-high mixed-use timber building in Brumunddal, completed in March 2019. Ratified by CTBUH as the world’s tallest timber building, Mjøstårnet consists of offices, technical rooms, 32 apartments, 72 hotel rooms, a restaurant, a conference room on level 17 and a rooftop terrace.
The main load bearing consists of large-scale glulam trusses along the façades as well as internal columns and beams. The trusses handle the global forces in horizontal and vertical direction and give the building its necessary stiffness. CLT walls are used for secondary load bearing of three elevators and two staircases, but do not contribute to the building’s horizontal stability.
The initiative to build Mjøstårnet comes from investor Arthur Buchardt. He grew up in Brumunddal and wanted to build the world’s tallest timber building using local resources, local suppliers, local competence and sustainable materials. The completed building has a majority of wooden components originating from nearby sustainable forests. The glulam structures were produced at Moelven’s glulam factory only 15 kilometers from the site.
When designing tall timber buildings it is crucial to find smart ways to cope with horizontal accelerations induced by wind. Recommended comfort criteria are given in ISO 10137 and guidelines for calculations are given by EN 1991-1-4. Particularly important is the structural damping ratio, which influences the result very much. Damping can be derived from measurements and data collection taken on site. During construction NTNU installed accelerometers to monitor the building’s behavior, providing important information on how the structural skeleton behaves.