Tangenvika Railway Bridge, Norway

Norwegian authorities are improving rail connections between Oslo and other cities by means of the Intercity Project. One of the elements of the so-called Intercity Project is the development of double tracks for high-speed trains on the Oslo-Lillehammer line. This together with a substantial reduction in the length of track. This reduction requires a 3 km long tunnel and the longest railway bridge in the country. Near the village of Espa on the banks of lake Mjøsa, one of the largest lakes in Norway, the project plans a kilometre-long bridge across the bay at the peninsula of Tangenvika.

In collaboration with Iv-Consult, ZJA conducted an enquiry into the possibilities and limitations of such a bridge, consisting of twenty 50-meter spans, and two spans of 35 meters, designing it as a self-supporting construction out of wood resting on concrete columns. Iv-Consult went ahead with a thorough technical enquiry. This resulted in the comparison of five different design options.

Laminated wood

Nowadays wood offers architects a lot more options than only trees turned into timber. Laminated wood has considerably better constructive and predictable properties, has more strength and can also be shaped to form arches.  By working with laminated wood, the desired property, shape and size can be determined. This allows construction elements to be made that can be integrated into a beautiful and larger whole. Spruce and pine wood can be sourced locally in Norway and are an obvious choice when it comes to value for money. In some designs a combination with higher-quality woods and steel reinforcements is required, other types of design require a higher volume of wood.

The arch bridge

The technical research compared designs with continuous and non-continuous beams and looked at solid and hollow constructions and options with an open beam construction. The most cost-effective, strongest and most appealing designs survived. From the last four remaining options, ZJA chose one to be the focus of further research. This design is an arched bridge from laminated, curved beams, resting on custom-made lozenge-shaped concrete columns, to distribute the forces. One of the advantages of this design is that it can be largely prefabricated and assembled on site. Its proportions, the interplay of wood and concrete, the straight and arched lines seem to offer the most harmony of all the designs. The rectangular robust columns and the rhythm of the relatively long wooden arches over the bay are a fitting addition to the precious landscape.