Tikkurila Railway Station and Shopping Center, Tikkurila, Finland

Tikkurila is the administrative heart of the City of Vantaa and one of its regional centers. It is home to the third busiest station on the main rail line. There are frequent bus connections from Tikkurila to Helsinki Airport. After completion of the new ring railroad, there will also be a frequent rail service. An impressive new group of buildings is emerging in the area around Tikkurila station. They will be known as "Dixi", a name chosen by public vote. The principal architect is Rainer Mahlamäki from Lahdelma & Mahlamäki Architects. Dixi's first phase, which was completed in 2014, includes a shopping centre, an office tower, a bus terminal, and a car park. Most of the permitted building area is in a structure with a gross floor area of 33,200 m2, completed in the fall of 2014. The project will continue in 2015 with phases 2 and 3 as buildings stretch out toward Hotel Vantaa. The station's ticket office and bus terminal will move to the new building and the current structure will be demolished to make way for new buildings. The second phase includes a gross floor area of 16,000 m2 and the third phase includes 6,800 m2. "The shopping centre will occupy three floors. Floors 4–11 will be occupied by offices. A decision was made to build the shopping centre and office space using a steel-framed composite structure. A five-story building, cast in situ above the bus terminal, will be occupied by station facilities, commercial premises, and a car park with space for 500 vehicles. It will have a green roof covering 6,000 m2," says Jyrki Haka, Site Manager for YIT Rakennus Oy, the construction company in charge of the turnkey project. Tenders were requested for the frame of the office building, which will form the southern part of the section currently under construction. The tenders were based on a composite structure of steel columns, WQ beams, and hollow-core slabs. The frame of the north section consists of reinforced concrete columns and post-tensioned beam-and-slab systems, both of which were cast in situ. The connecting area between the northern and southern sections contains long, variable spans. In this area, the frame consists of hollow steel section columns, steel truss structures or steel beams with hollow-core slabs, and post-tensioned reinforced concrete slabs cast in situ. "The composite structure is going up quickly. The steel frame and hollow-core slabs will be ready within six months. The schedule calls for the walls and roof to be in place before Christmas 2013, which is a good thing from the point of view of minimizing moisture in the building," states Jyrki Haka. "We held an extensive tendering competition. Peikko Finland's tender, based on its Deltabeam technology, proved competitive. As beams account for 60 percent of the office building's frame, ensuring that they could be reliably supplied played an important role in securing this contract. We chose KPA-Rakentajat Oy as our erector and they had positive things to say about the choice of Deltabeams, which also worked in Peikko's favor," says Tommi Gröhn, who was responsible for purchases at YIT. "Peikko fabricated the composite columns and trusses for the frame according to Finnmap's designs in accordance with Euronorms, and the Deltabeams according to its own workshop designs. We worked in conjunction with Finnmap and took responsibility for changing the designs to enable Deltabeams to be used instead of WQ beams. This meant that there were no extra costs for the customer," says Harri Onikki, Peikko's Project Manager. "We prepared the entire design using Tekla Structures. It was a great help to us in our work. Small tolerances and collision avoidance have been managed well. Column reinforcements were also a part of the model. We provided a model in AutoCAD format to Peikko. When the contract was made, we utilized Peikko's Tekla custom components to update the designs rapidly. The choice of Deltabeams also affected the connecting structures," says Tomi Eloranta, Principal Designer of steel structures at Finnmap Consulting Oy. "The model was invaluable for planning the installation schedule and order. We have one member of staff who focuses entirely on utilizing the model and developing it for use on the construction site. The Site Managers have lightweight versions for day-to-day viewing. The model has been particularly useful for visualizing truss structures," Jyrki Haka says. "Understanding the order in which suspended structures should be installed would have been very hard without layout diagrams," adds Tommi Gröhn.