The Vårdö bridge is taking shape
At Vårdö, 37 kilometres east of Mariehamn, in Åland, a new water passage is under construction. Graniittirakennus Kallio started up its demanding construction site at the beginning of 2017. Even though more than a year is left of the contract period, more than half the work is completed. In mid-June, the steel structure was put in place, while the casting of the bridge deck will be performed in the spring of 2018.
The construction of a waterway bridge is the prime test of an infra builder’s professional skills. At the end of 2016, Graniittirakennus Kallio won a bidding competition organized by the Åland Regional Government to build a new bridge at Vårdö.
– To build the 340-meter long composite girder bridge in maritime conditions is one of the most demanding challenges of the sites I have been involved with. Now that we have the steel beams in place, the biggest technical challenges are behind us”, says Pertti Heininen, Technical Director of GRK.
Heininen notes that his earlier linguistic experience from working in a Swedish-speaking environment has come in very handily for this project in the Åland isles, where Swedish is the sole official language. As a matter of recruitment policy, GRK has continued to select expert builders with versatile language skills. This is reflected also in the nomination of the site manager, Magnus Ahlskog, who as a citizen of Åland is a native Swedish speaker, but also is fluent in Finnish.
Ahlskog is also an expert on local conditions, who knows that weather must always be taken into account in the Åland Islands. – The wind speed limit for lifting the steel beams is in principle five meters per second. Ultimately, however, the crane manager decides when the weather is permissible, and when not. The northwest wind is the worst on this site, because the wind will push the crane towards the old bridge, which will not be dismantled until next year, Ahlskog says.
Lifting was the most sensible installation method
The Vårdö bridge is of the composite steel beam type, which is relatively common in Sweden, while in Finland it is more usual to select a fully concrete-based structure. The bridge columns are coated with stainless steel plate, and the bridge beams are painted with a multi-layer coating system, thus achieving a lifespan of 100 years in the marine conditions without any special maintenance.
There are five steel beams weighing more than 200 tonnes, ranging in length between 60 and 70 meters. Similar bridges in Finland have most commonly been erected by the launching method, i.e. by joining the steel sections successively on land, while pushing the bridge forward over the support, a section at a time. Instead, the bridge at Vårdö was installed by lifting each beam into its final position on the column supports, awaiting its connection to the main bridge by welding up the joints.
– Most of the welding work was carried out at the Ylivieska plant, and finished up at the port of Rauma. The construction site only had to connect the large sections to each other, site engineer Isto Ahlqvist explains. According to him, the installation method was a result of GRK’s initiative, as the work site was very cramped, making the launching process very difficult to apply on the site.
– The client welcomed our proposal. All in all, the client organization has been quite satisfied with us. This includes Mika Nordberg, Minister of Infrastructure for Åland, who visited our construction site, Ahlqvist explains.
Reinforcing in the winter, casting in the spring
The first year at the construction site went according to plan. Last summer, foundation slabs were cast at five metres depth on top of 20-metre drill piles. The autumn was used in preparing and installing the bridge support pillars and beams. In April 2018 we will start casting the deck slab, having spent all winter preparing the formwork and the reinforcement for the 340-meter long bridge deck, Pertti Heininen explains.
The new bridge will be taken into use at the end of 2018. Another half a year is then left to pull down the old bridge, which structurally resembles the new one. We will probably handle the dismantling phase quicker than that, Heininen says.