The Norwegian construction firm Reinertsen is erecting a new bridge between Løding and Vikan in northern Norway, for the Rv 80 trunk road. This Trondheim-based company decided to work with Doka because of the positive experience it had had on previous projects: In fact, the extensive advisory and planning services and high safety standard provided by Doka were crucial factors underlying the decision. The Rv 80 road-building project aims to link the Tverland peninsula better to the regional capital of Bodø – some 1200 km north of Oslo.
The Tverlandsbrua is 670 m long, has a longitudinal gradient of as much as 4.5 %, and is being built in the form of a spiral transition curve with varying radii. It crosses the Saltfjord between Løding and Vikan, in seven spans borne by six piers of up to 13 m in height – three of them are twins. Doka has four of its Cantilever forming travellers (CFTs) in action at this site. Because of the large – 22.6 m – width of the superstructure deck, they are built with three longitudinal trusses, from rentable components. The slanted webs made it necessary to widen the bottom formwork; this, in turn, meant that the bottom grid – including the platforms – had to be slide-mounted. In this way, the site crew can adapt the bottom formwork to the next segment quickly and safely. The modular design concept of the CFTs also makes for efficient, cost-saving adaptability to the different cross-sections of the superstructure deck.
Super-sturdy shoring construction
When it came to building the three bridge piers from which the CFTs were to start travelling, an exceptionally strong formwork solution was needed: In stormy weather, the up to 10 m high waves out in the fjord put the equipment fielded here through an absolute endurance test – which the Large-area formwork Top50 and Wall formwork FF20 systems used in building these piers passed with flying colours. The twin piers were each poured in a single casting step. To stabilise the formwork, platforms were built onto the foundations beneath the piers; the high wind loads were then transferred into these platforms by spindle struts. CFT beams (from the cantilever forming travellers) and SL-1 system beams were used in constructing the platforms.
This equipment was also used to help construct the pier-heads – a custom solution that has worked very well indeed: The beams rested on horizontally mounted Doka supporting construction frames, enabling them to sustain the load from the widely cantilevering pier-heads. The pier-heads were poured in three casting steps: Large-area formwork Top 50 was used to form the bottom slab, Large-area formwork Top50 and Wall formwork FF20 to form the webs, and the Bridge formwork ParaTop, Large-area formwork Top 50 and Load-bearing tower Staxo systems to form the deck slab. Using ParaTop meant that no shoring was needed for the cantilever arm formwork – which also kept the equipment commissioning-quantity small. A particular challenge here was that it had to be possible to lower the screwjack mechanisms after the first casting segment, so that the bottom slab could carry its own weight: this meant that when the webs were poured, it was already possible to transfer the load into the piers by way of the bottom slab.