1. Treet – 14 floors in Bergen Växjö, Sweden. 2015-09-24
Rune B Abrahamsen Senior Vice President at Sweco, Lillehammer, Norway
The 4th Forum Wood Building Nordic. Växjö

2. Project group
In 2010 BOB proclaim that they want to build the world’s tallest timber building.
The following project group was established
Sweco – engineering
Artec – architecture
Moelven Limtre – glulam and CLT structures
Kodumaja – building modules
Designwork
Supported by:
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3. 4th Forum Wood Building Nordic. Växjö
Sweco
Sweco is one of Europe’s leading companies in consulting engineering, environmental technology and architecture
9 000 employees in 12 countries
assignments per year
customers
Sweco has about 100 offices in the Nordic region
4th Forum Wood Building Nordic. Växjö

4. Where is Bergen?
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5. Location
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6. The plot in Bergen
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7. 4th Forum Wood Building Nordic. Växjö
Bergen, Norway – 14 storey building
Construction of “Treet” (The tree) is almost finished.
In November 2015 the residents can move in
Net area of 5830 m2
A Sweco webcam service is providing live pictures from the building site
Google Sweco+webcam
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8. Inspiration from timber bridges
Technology developed for timber bridges over the last decades opens many doors.
The experience gained from bridges can be used for tall buildings 
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9. Inspiration from timber bridges=
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10. Innovative structural system
Total height 49,4* (52,8) m
550 m3 glulam
385 m3 CLT produced by the German manufacturer Merk
The building stands on top of a concrete garage piled to the bedrock
Light weight building > tension anchorages. 940 kN Drawn in Revit. 3D. BIM
* Height defined by council on tall buildings and urban habitat
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11. 4th Forum Wood Building Nordic. Växjö
Structural system
Calculated using the software Robot
Glulam carries all vertical and horizontal loads
71 mm max horizontal deflection (Level 14)
CLT is used in the staircases, elevator shaft (15 st.), some inner walls and balconies, but is not structurally connected to the glulam
Prefabricated timber frame building modules are inserted in the “cabinet rack”
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12. 4th Forum Wood Building Nordic. Växjö
Concrete slabs
Prefab. concrete slabs in 5., 10. og 13./14. level has several functions:
Foundation for modules
Adds mass to the structure which improves the dynamic behavior
Temporary roof during construction
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13. 4th Forum Wood Building Nordic. Växjö
Structural system
Modules are stacked up to 4 storeys, and are only connected to the main structure in the lowest module
Large glulam sections are block glued
Typical column: 405x650 and 495x495 mm
Typical diagonal 405x405 mm.
Glulam quality GL 30c and GL 30h according to EN 14080
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14. Engineering choices
Sweco used glulam trusses for this 5 storey complex in Trondheim in This was used as a basis for high-rise
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15. Engineering choices
To limit the need for maintenance a permanent weather protection system was chosen.
The north and south facades have glass to protect the timber structure
The east and south facades have metal cladding
In this way the timber can be regarded as protected
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16. Engineering choices
To reduce the work on site and reduce building time, we wanted to prefabricate as much as possible.
Timber frame modules
Each module / apartment complies with the passive house standard
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17. 4th Forum Wood Building Nordic. Växjö
Building modules
Modules are stacked up to four levels high
Single level in the power storey
The stacked modules are only connected in the bottom to the slabs.
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18. Typical plan
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19. Structural fire design
Timber is not a pre-accepted material for highrises in Norway. However, Norwegian regulations open up for alternate materials as long as required documentation is produced
Fire design is done according to the Eurocode.
Timber can burn. In this project the glulam is so thick that we allow it to burn for 90 minutes without failing. No extra gypsum is used on the glulam.
All steel connections are hidden inside the timber. In this way it will not fail within the required fire resistance time
In addition there are sprinklers, pressurized escape stairs and painted surfaces to improve fire safety
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20. 4th Forum Wood Building Nordic. Växjö
Serviceability
Lack of information on dynamic values. Testing was needed!
Norwegian University of Science and Technology, NTNU, performed the tests.
The Estonian company Kodumaja provided modules.
Non destructive testing of similar modules.
Impact hammer and accelerometers.
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21. 4th Forum Wood Building Nordic. Växjö
Results, serviceability
Results plotted into evaluation curves given in ISO 10137:
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22. 4th Forum Wood Building Nordic. Växjö
Summary of findings, accelerations
Residents in the top floors might in rare cases feel vibrations, but it is very unlikely that they will become uncomfortable.
The chosen structural solution for "The tree" using glulam truss works and stacked prefabricated building modules gives a robust design and most probably insignificant effects from vibrations caused by wind exposure.
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23. 4th Forum Wood Building Nordic. Växjö
Further work, accelerations
Install accelerometers and anemometers (to measure wind velocity) (NTNU)
Measure the actual accelerations and damping
Accelerometers placed both on the truss work and on the building modules.
This will give unique test results for a timber high-rise.
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24. Pictures from the construction
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25. Pictures from the construction
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26. 4th Forum Wood Building Nordic. Växjö
How was it possible ?
Job owner who was willing to take some risk, but believed in the project.
Early involvement by experienced glulam and module manufacturers.
Cooperation between job owner, architect, engineers and suppliers throughout the process
Political support
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27. Spin-off project. Brumunddal
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28. Spin-off project. 17 storeys
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29. Conclusive remarks
Timber high-rise is a good answer to sustainable building in urban areas
The chosen concept is robust and feasible
It’s possible to build lower and higher with this building system
Given a new chance, we would build it again!
Feel free to challenge the world record!
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30. Thank you for your attention!
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