Bridges

Bridge facts

Number of bridges:	18199
Longest bridge, Drammensbrua:	1892 m
Longest suspension span, Askøybrua:	850 m
Average bridge length:	250 m
Number of ferry quay bridges:	362
Total bridge length:	446 km

                                                    

BRUTUS – the management system

BRUTUS is a modul-based, modern IT system for administering, operating and maintaining bridges. The project is developed as a cost-effective tool for management and supervision of bridge-related work tasks. BRUTUS has been successfully implemented in Latvia and Tanzania .

Concrete bridges
Concrete bridges represent a major part of the total number of bridges. During the last half century long concrete bridge spans have been dominated by the segmental cantilever method. In 1998 the world record for this type of bridges was in fact beaten twice, first by Raftsundet bridge in the county of Nordland with a main span of 298 m. Later the same year Stolma bridge in Hordaland added 3 m to that record with a main span of 301 m. On these large bridges, high strength lightweight concrete is used in the superstructure to reduce weight.

Steel bridges
Effective protection against corrosion is decisive for the steel bridges’ ability to compete. Our duplex protection system with thermal sprayed zinc has been used for a period of 40 years. The top coat has to be renewed every 20-30 years. Dehumidification techniques were improved during the seventies. Today we mainly build girders with trapezoidal boxes where the concrete bridge deck works in composite with the steel box. In this way we achieve a clean outer surface, easy to repaint. Inside a dehumidifier create a non corrosive environment. Main spans vary up to 120 m.

Timber bridges
Under the lead of the NPRA, timber has become a viable bridge construction material in Norway during the recent ten years. An increasing number of pedestrian as well as road bridges have been built, including world record span for modern timber road bridges of not less than 70 m. The most frequently used structural systems are arches and trusses and the bridge decks are almost exclusively stress laminated timber plates. During the recent ten years about 60 timber bridges have been built of which half are road bridges. In addition, a number of bridges have been built by the railway administration, local authorities and private interests.

Cable stayed bridges
During the last 30 years we have built 6 cable stayed bridges with main span from 155 to 530 m. Among these are the award winning bridges of Skarnsundet and Helgeland (FIP award 1994).Skarnsundet bridge was the world’s longest cable stayed bridge when it was opened 1991, and is still one of the longest with concrete girder.

Suspension bridges
From 1956 to 1982 we built 16 suspension bridges with truss girder and span from 200 to 525 m. After 1992 we have built 7 suspension bridges with aerodynamic box girder and span from 335 to 850 m, all two lane bridges.

The design of a bridge with a main span of 1310 m is expected to start 2006. Because of low traffic only two lanes is needed, and this bridge is going to be one of the world’s most slender suspension bridges.

Floating bridges
Two floating bridges have so far been built in the public road network. The award winning Nordhordland bridge (ECCSEuropean Award for Steel Structures 1995)is the most known with a floating span of 1246 m between the abutments. A horisontal curved steel box girder is supported by 10 lightweight concrete pontoons, spaced 114 m. Because the fjord has a depth of up to 500 m, the floating part is fixed only at each end, without any anchorage system to the sea bottom.

Submerged floating tunnel
Submerged Floating Tunnel is a new type of structure yet to be built. The concept is a tunnel, steel, concrete or both, being kept in position some depth below the water surface, not being a barrier for surface traffic. Because of being positively bouyant, the tunnel has to be anchored down to sea bottom or held in position by pontoons on the surface. The NPRA has, in cooperation with contractors and consultants, developed four alternatives of the submerged floating tunnel, three in concrete and one in steel. These four alternatives were officially approved to fulfill the requirements for crossing the Høgsfjord, a fjord 1500 wide and with a maximum depth of 170 meters. The project was unfortunately stopped due to changes in regional plans.

R & D
A two lane, network arch with a main span of 220 m, which is the world’s longest span for this type of light and slender construction, is now being designed for construction.

Norwegian engineers are developing the hybrid solution“Bridge Symphony”for long span, slender bridges. The innovative technology under development is intended to enable the construction of bridges with span of up to 3 kilometres.  “Bridge-symphony”is a patented innovation designed by the NPRA in cooperation with the engineering firm Dr.Ing Aas-Jakobsen AS.