Post-tensioned structures save concrete and steel in parking facilities
Sweco and Naulankanta, professionals of post-tensioned structures, have implemented several projects together, such as parking facilities in Hatsala, Kuopio, and Uusikumpu, Espoo. The worksite-friendly tensioned frame solutions help save both construction time and materials.
Naulankanta Oy is an expert on post-tensioned concrete structures that has worked together with Sweco’s structural engineers for several years now. The parking facility projects are progressing smoothly, as the long cooperation has resulted in mutual trust and respect.
“The key is that the basics work, such as the availability of engineers and active communication,” says Ville Simonen, the project manager of Naulakanta’s project development.
Sweco’s familiar structural engineers know well Naulakanta’s production and implementation methods, expansion joint equipment and the frame tension system that is not used by anyone else in Finland. “Together, we can make the most of our systems and apply the most effective solutions.”
Structural solutions helped with Uusikumpu’s cost pressures
At the moment, Sweco and Naulankanta are designing and building a 5.5-storey parking facility for Varma Mutual Pension Insurance Company in Uusikumpu, Espoo. The project’s main contractor is VRP Etelä-Suomi Oy.
The parking facility serving the residents and commuters of the area includes 285 parking spaces, most of which will be equipped with charging stations for electric vehicles. Additionally, solar panels will be installed on the roof. According to Sweco’s project manager of tensioned structures, Santeri Määttä, the worksite stage has proceeded quickly. The concrete frame of Uusikumpu will be implemented as a cast-in-situ beam slab.
“Together with Naulankanta, we have since the beginning been thinking about a frame solution that would allow for as efficient mould cycle as possible. Correctly timed stages of the worksite help reduce the project’s duration even by weeks, resulting in savings in total costs.”
And there has been a great deal of pressure on costs in Uusikumpu. Material costs have clearly increased since the beginning of the project. According to Simonen, the projects often require creative co-development. “This time, too, we were able to find solutions improving the cost efficiency of the frame and the base floor structure together with the engineers.”
Efficient space use in the Hatsala parking facility
The other ongoing parking facility project is in Hatsala, Kuopio. The project’s main contractor is Rakennusliike Lapti Oy. The residential and service block of Kotikatu 365 Oy has about 500–600 apartments and a parking facility for 433 cars. Charging stations for electric cars can be added to all parking spaces, and the basement floor has a bike storage for 270 bicycles.
“We have been in active dialogue with Naulankanta, and we agreed right at the start of the project what kind of frame solution would be used in Hatsala,” says Sweco’s project manager Alexander Westerholm. Due to its large size, the parking facility has been divided into two expansion joint blocks. “By designing the placement of expansion and construction joints carefully, we were able to achieve highly efficient mould cycle, allowing a quick frame schedule.”
The number of parking spaces is very high in Hatsala compared to the surface area, and parking spaces have also been placed at the ends of the facility. The facility will not have a roof, which allows placing parking spaces also on the top level. Steel grids were used as stiffening structures of the exterior walls, installed after the casting work of each level.
“This way, the installation of the grids will not slow down the frame’s construction pace,” Westerholm states. Retracted pillars were used in Hatsala, which shortened the beam spans and left enough room for the technology on the sides of the parking facility. The volumes of tendons and reinforcements also dropped, making the structure more efficient. “Post-tensioning allows for optimising the structural thickness, which saves concrete.”
In addition to having a smaller carbon footprint, post-tensioned concrete structures offer other benefits to parking facilities. The number of vertical structures, i.e. pillars, can often be reduced, which gives more space to the parking facility – a factor valued by many drivers. In addition, there are fewer joints compared to a parking facility with a precast construction: a cast-in-place, post-tensioned concrete structure is automatically watertight when completed.