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FEM-Design Glitne in Umeå

Wood meets steel with smart analysis in FEM-Design

Due to their excellent environmental profile, interest in wooden structures continues to grow. Working with wood also gives architects the opportunity to reinvigorate their design methods. A perfect example of this is Glitne, in central Umeå. Situated 25 meters above ground, on top of an existing city block, this beautiful structure has a vibrant green sedum roof. Wood has been used in conjunction with steel in the frame of the building, which contains 49 apartments. The developer on the project is Blaticgruppen Bygg AB.


ILLUSTRATION: BIG | Bjarke Ingels Group

“The building’s architecture is innovative, providing distinct challenges to the materials used in the frame. Therefore, steel reinforcements are needed to solve these challenges”, says Peter Fajers, Technology Officer at Sigma Civil.

He continues  “The wooden frame uses a relatively new component called CLT (Cross-Laminated Timber) panels. These are made of alternating bonded wooden boards, giving stable performance under load in all directions. Dimensions of the panels are 16 m by 3 m, with a thickness of 120 mm. These wooden slabs make the architecture of the structure possible and give Glitne its special character.”

The repeated global and local analysis provides the right design

Peter and his colleagues analyzed this complex construction in order to gather information about the design requirements of the elements used. In this regard, FEM-Design has been instrumental in studying the interaction between materials – in particular, the critical connections between wood and steel. Using a distinct working method, evaluations from one part of the structure are later analyzed within the entire model – the interaction between local and global.

“Our work in FEM-Design was carried out through a global analysis, in other words, the entire construction”, Peter explains. “But also, locally, where we used smaller models in the program and studied how the connections acted. In this way, we got the right amount of stiffness and were able to see how it affected the entire structure at the same time. New evaluations were added and repeated, achieving a rate consistent with the documented guidelines. By alternating from local to global and back again, the correct specifications were achieved.”

Another task for Peter and his colleagues was predicting the distribution of loads. This was especially important, as they not only had to consider the new building but also the existing one, right down to foundation level. “Fire requirements are very stringent. To increase fire safety, burn-ins were considered, together with additional plasterboard and housing sprinklers. The burn-in will affect the CLT panels, and calculations for residual cross-sections in fire load cases were also done in FEM-Design.”


ILLUSTRATION: BIG | Bjarke Ingels Group

Acoustically challenging

Another challenge for the team was the fact that no sound should be transmitted between apartments. Together with Martinsson, who delivered the CLT panels, Sigma Civil has developed a special acoustic connection between units. The result – sound doesn’t spread.

“In the global analysis, we looked at horizontal stiffness and how audio connections behave – the results they give, and how that is affected when apartments are connected in the core of the unit.”

The work in FEM-Design again shifted between local analysis and the effect these features have on the entire model. Everything is connected, and the changes in one part can have a knock-on effect for all apartments. The program is much more than analysis and calculations however – at Sigma Civil, it was also used to evaluate and make decisions:

“We used FEM-Design in several different ways throughout the project, and it has helped us to verify multiple solutions and alternatives.”

FEM-Design has proved highly successful in making Glitne’s advanced construction possible, bringing together wood and steel in perfect harmony. This, in turn, meant that the architect’s distinctive housing design was fulfilled.

Interview by Love Janson, ComWise AB

FACTS

Location: Umeå

Software: Strusoft FEM-Design

Developer: Balticgruppen Bygg AB

Structural engineers: Sigma Civil


ILLUSTRATION: BIG | Bjarke Ingels Group

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