A tour de force in wood

TiC hears from Tekla Structures on 3D modelling software used for designing complex wood structures. 

SO JUST what type of software do you need to build one of Europe’s tallest wooden office buildings?

The Finnforest Modular Office (FMO) in Finland, is a five-storey, 13,000 sq m structure built using both prefabricated and separately worked wooden parts, as well as steel and concrete elements.

The £15m building was detailed and built utilising advanced 3D planning and modelling techniques by Tekla Structures.

Tekla’s model-based software products are used mostly in construction and its advanced 3D models contain all the information required for the different phases of a project.

Built in 2005, the FMO has offered a wealth of information for future projects.

Structural design
WSP Consulting Kortes carried out the structural design for what was its first wood project implemented with 3D modelling.

“We’d already been using Tekla Structures to model all our steel structures for some years,” says Ville Jaatinen, project engineer at WSP. “We’re also using the same system to an increasing extent for concrete structures, but this was the first time we used Tekla Structures for wood.”

The starting points for the project were unconventional use of wood, the life-cycle properties and environmental effects of the materials, energy efficiency, indoor climate, as well as the lighting and acoustics effects.

Wood based solutions, together with concrete and steel, require special expertise to carry out. As wooden technology had not been utilised in this magnitude previously, the entire project was a learning curve for all parties.

What made things somewhat easier, however, was the role of Tekla Structures in the detailing and modelling of the building. 3D planning in this case presumed significant development work in order to be able to efficiently model the new kind of wooden elements with their connections.

WSP utilised Tekla’s advanced 3D building information modelling (BIM) solution, an information management process, where a building of any size, material or complexity can be virtualised in detail with every nut and bolt in place.

Ville Jaatinen said in the design, wood brought a change of perspective, starting from dimensioning. “This was something brought to the fore with structures like glulam, which can be regarded as one or many objects at the same time,” Jaatinen explains. “We ended up defining two different kinds of holes for connection pieces: holes with a 1mm tolerance for steel parts and holes with a zero millimeter tolerance for wood parts.”

The then latest features of Tekla Structures, such as a drawing classifier and printing wizard, were utilised extensively. “Notches were modelled as correctly-dimensioned notch material and the related texts were imported to assembly drawings based on material and length,” Jaatinen says. “In addition, the wizard was used to import a lot of neighbour parts to the assembly drawings to help fasten connecting pieces at the factory.”

Future projects
Jaatinen says the more recent versions of Tekla Structures provide increasingly better means for solving many of the challenges encountered during the FMO Tapiola project. “We would have had a lot of use for the option to define varying finishes on a part’s different surfaces, as is possible with newer versions,” says Jaatinen. “It would significantly enhance work with edge-laminated beams. Another useful improvement is the custom component function, which was still under development in the Tekla Structures version used for the project. I’m sure that the custom components currently available are already applicable for connections, too.”

The 3D model was also successfully utilised to produce part, assembly and dxf drawings as well as a considerable number of reports to enhance production. “I believe we were able to significantly cut down on errors by using 3D modelling,” says Jaatinen, “it also improved the quality of building compared to the alternative of designing in a traditional 2D environment. Even though there were truly difficult structures and complex details, I never heard of a single problem on site.”

Following on from the success of the FMO Tapiola project, Tekla has worked with steel fabricator SH Structures for two award-winning projects in 2006: the new Alnwick Gardens Pavilion and Visitors Centre in Scotland and the Riba-award wining Welsh Assembly.

“We’ll be much better equipped in the next project,” adds Jaatinen. “When similar wood projects are implemented, I’m in no doubt that Tekla Structures will be brought into play again.”