Treet - The world s tallest timber building

Treet - The world s tallest timber building M. Sc. Rune B Abrahamsen Sweco, Lillehammer, Norway

Sweco Sweco is one of Europe s leading companies in consulting engineering, environmental technology and architecture 9 000 employees in 12 countries 1 billion net sales 37 000 assignments per year 15 000 customers

Timber high-rise - Sweco Norway has previously done feasibility studies on tall timber buildings - Barentshus in Kirkenes, Norway. 20 storey office building - Rundeskogen in Stavanger, Norway. 15 storey apartment building.

2007. Rundeskogen, Sandnes 15 storey timber apartment building with concrete core

2010. Barentshouse, Kirkenes 20 storey office building. Timber only

Timber high-rise - We found that timber high-rise buildings are feasible from an engineering point of view - Timber high-rise buildings are a good answer to sustainable building in urban areas - The cost of building is somewhat higher than steel/concrete. But erection time is shorter. - The carbon footprint is favourable - These buildings can be aesthically pleasing in their design - Many people want such buildings.

Melbourne, Australia 10 storey building 10 storey CLT building. Presently regarded as the tallest timber apartment building in the world.

Experience with timber structures Sakyamuni pagoda - 1056 67.3 m tall including the 11.3 m spire on top Maybe the tallest timber building on the planet today In Sichuan, earthquake zone in western China 8

Experience with timber structures Stave churches of Norway Hopperstad stave church Built between 1150-1200 One of 40 remaining churches Timber is durable! 9

Experience with timber bridges 1996 - Evenstad bridge. 180 m long Designed for two lane full traffic 10

Experience with timber bridges 2011 Bridge crossing the motorway outside Oslo airport. 50 m span 11

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

Project group Bergen- og omegn boligbyggelag (BOB) is a Norwegian housing association. Part of their strategy is to build sustainably in urban areas. 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 glulam and CLT structures Kodumaja building modules 13

Where is Bergen? 14

Location 15

The plot in Bergen 16

Bergen, Norway 14 story building Treet (The tree) is under construction now. The first timber elements were installed last month. Residents can move in autumn of 2015. Net area of 5830 m 2. There is a webcam service in operation

Facts - Total height 49,4 (52,8) m - 550 m 3 glulam - 385 m 3 CLT - The building stands on top of a concrete garage. - Foundations piled to the bedrock - Drawn in 3D. BIM. Autodesk Revit. 18

More facts - Calculated using the software Robot - Concrete decks serve as extra weight as well as platform for modules - 71 mm max horizontal deflection (Level 14) - Prefabricated timber frame based building modules are inserted in the cabinet rack 19

Even more facts - Large glulam sections are block glued - Typical column: 405x650 and 495x495 mm - Typical diagonal 405x405 mm - Glulam carries all vertical and horizontal loads 20

and then some facts - Wind load from 8 directions was applied for design - The building is not designed for seismic loads. It s so tall that the wind load prevails, which means that seismic design can be omitted according to Norwegian code - Highest compression force in a column is 4287 kn = 437 tons 21

Engineering choices - We chose to use proven technology for connections of large timber structures. Slotted-in steel plates and dowels.

Engineering choices - The connection was developed for the Olympics in 1994. It handles very large forces in arenas and bridges.

Engineering choices - Sweco used glulam trusses for this 5 story complex in Norway in 2005. This worked well and was chosen as a basis for the high-rise system

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

Engineering choices - The main load bearing is handled by glulam alone. CLT is used in the staircases, elevator shaft (15 stories), some inner walls and balconies, but is not structurally connected to the glulam - Concrete decks are used on three levels in the building mainly to improve dynamic behavior, but also to serve as platforms for stacking building modules

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

Engineering choices - Conventional prefabricated building modules can be stacked up to 6 storeys high. 14 storeys is too much, therefore an additional load bearing system is necessary. Stacking 4 storeys is quite economical. - Variants of building modules should be held to a minimum to ensure lowest possible cost. In this way a serial production of modules can be done - Using modules reduces the challenge with water/moisture in the building phase considerably - The modules from Kodumaja are based on timber frame. - Each module/apartment complies with the passive house standard

Engineering choices The basis is timber frame work. Timber beams in floor and roof. Plasterboard. Oak parquet. Dishwasher. Cupboards. Kitchen. Shower. Tiles etc. All technical installations such as sprinklers, electricity, water pipes, cable tv etc are also integrated in the modules

Building modules Modules are stacked up to four levels high Single level in the power story The stacked modules are only connected in the bottom to the slabs.

Typical plan 31

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

Fire design 8 mm steel plates 12 mm dowels

Serviceability Lack of information on dynamic values. Testing was needed! Norwegian University of Science and Technology, NTNU, performed the tests. Non destructive testing of similar modules. Impact hammer and accelerometers.

Finding damping of modules 35

Modelling of modules - Damping of modular walls has been physically tested and simulated - NTNU (University of Trondheim) and Kodumaja of Estonia have contributed to this - The building modules have a damping of about 3% 36

Results, serviceability Results plotted into evaluation curves given in ISO 10137:

Conclusion, serviceability 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.

Assembly. Step by step

Picture taken 2 months ago 48

Picture taken last week 49

Webcam in operation You can follow the construction process and check out videos using this link: http://www.sweco.no/no/ Norway/Nyheter/2014/ Webcam_Treet/ Google Sweco+webcam 50

Costs Construction costs are comparable with similar building in steel or concrete. But, BOB do not reveal construction costs or budgets at this time. Treet is a pilot project, and costs for development and innovation have been financed by BOB. Average price for apartment: 5800/sqm 51

Main challenges - Comfort criteria. Low weight -> higher accelerations - Obtaining structural data for building modules - Safe work operations in the air - Avoiding moisture during erection - Designing maintenance friendly solutions - Getting the fire concept approved and implemented - Project economy. Risk control to avoid overpricing from suppliers not familiar with the concept 52

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 Feel free to challenge the world record! 53

Make a visit to Bergen next year! Thank you for your attention! 57