Safety and functionality of the structures of the Olympic Stadium verified on site

The Olympic Stadium, selected as the repair construction site of the year, has required seamless cooperation from Sweco and Skanska. Sweco is responsible for designing the repair and new construction and structural engineering at the site, and the challenges of the exceptional site have been overcome one by one in good cooperation.

Planning the renovation of the Olympic Stadium began in 2013, and the implementation was planned in a way that leaves most of the new structures hidden. As for the design of the site, the Olympic Stadium is far from ordinary. The designers have matched new structures with ones as old as 80 years, some of which are protected by the National Board of Antiquities. The aim has been to preserve as much of the old as possible.

Together towards a new Olympic Stadium for all people

Over 120 companies operate at the stadium site daily, so successful progress of each stage requires functional cooperation. Indeed, the spirit at the site resembles that of alliance projects.

“All participants are as proud as we are to be involved in a project this challenging, important and inspiring,” says Juha Kukkonen, steel structure specialist at Sweco. Solutions are developed between the construction project manager, Skanska, designers and subcontractors in an open atmosphere. “Everyone has a common goal in the project, and we work hard to reach it. This is why it is always nice to go to the site.”

The project utilises a Big Room day once a week, during which the designers, the construction project manager and the contractor go through the designs and possible problems. If necessary, separate meetings are also held.

“Big Room has proved to be a day that advances the design and allows us to make decisions really quickly,” says Hannu Tervo, design manager at Skanska. Skanska’s project management contract also includes developing the designs during construction together with designers of different fields. “Cooperation with Sweco has been good and active, and the design schedules have been specified along with the progress of the construction.”

According to Tervo, the most challenging parts of the site have been designing the steel structures of the new canopies at the stands and the renovation.

“This is complicated by the fact that, with repair construction, we never know what we come across during the demolition. Even difficult decisions have been made in good cooperation. Sweco has met the challenge, their reaction time has been quick and designs have been provided as needed. All designs have been made in a way that allows the work to be performed safely.”

Algorithms were combined with presence in the steel structure design

The Olympic Stadium features designs of exceptional steel frame, column and arch structures. The entire design has required the expertise of over 30 Sweco designers in total.

“Normally, we only visit the site for structure and frame inspections, but at the Olympic Stadium we have been present several times a week, when necessary,” Kukkonen says. The exceptionally tight presence has been essential for the progress of the project, and the design team has been flexible according to the situation. “It has been great to see how broad an expertise we have at our company.”

The dynamic geometry of the new canopy structures has required innovative structural design. The elevation of different sections of the canopy can be as much as eight metres apart. The eaves resembling the wing of an aeroplane are also challenging, as they narrow down to less than 30 centimetres at their thinnest.

“Implementing the canopy structures has required solutions different from normal construction practices, such as friction joints and almost 100 structural bearings. The management of the geometry of the edge of the thin eaves and other design solutions would not have been as efficient with normal practices, and therefore we have utilised algorithm-based design and parametric modelling,” Kukkonen says.

Repair construction 20 metres above and 15 metres below ground

The design process of the Olympic Stadium has also been unique to Harri Makkonen, who has worked in the industry for over 30 years. This repair construction expert has spent about half of each workday at the site for months.

“Constructing the new canopies up to about 20 metres high has changed wind load as the work has progressed and affected our work with the columns below ground,’ Makkonen says.

Reinforcing the old structures has required extensive rock excavation at each section of the stands up to 15 metres deep. The largest source of anguish for the Sweco designer has indeed been the support during construction.

“To be able to extend the old concrete columns deeper underground, the entire stadium had to be supported on steel structures for about 1.5 years. Ground investigations were not available on all sections, but we had to make sure that the excavation would not damage the old concrete structures. Reinforcement was very precise work! Luckily, everything went excellently and the new columns were cast without a hitch,” says Makkonen, relieved.

The reinforced concrete beams of the main stand were also fortified, but the look of the stand was aimed to be preserved. “The beams were supported with a rather rare solution: carbon fibre strips glued to the reinforced concrete beams. The structure will withstand heavier wind and snow loads than before, but it is so light and subtle that nothing is visible outwards,” Makkonen says.