Specifications
The bridge consists of three sections, a cable-stayed bridge, a pontoon bridge and a viaduct which connects the two. The cable-stayed bridge consists of a 99.3-meter (326 ft) tall H-pylon with a foundation at Klauvaneset on the mainland of Bergen. It supports a 172-meter (564 ft) main span, with the other end being fixed in a foundation 30-meter (98 ft) below mean sea level, which is anchored in the ridge Klauvaskallen. The whole cable-stayed bridge is 369 meters (1,211 ft) long, with a 190-meter (620 ft) long viaduct, supported by six pairs of pillars. The cable-stayed bridge allows for a sailing channel which is 32 meters (105 ft) tall and 50 meters (160 ft) wide. The main span is built in lightweight LC55 concrete, while the viaduct and pylon is built with conventional C45 concrete. Inside the pylons is a 1.6 by 2.0 meters (5 ft 3 in × 6 ft 7 in) hollow area.
The bridge has 48 cables, 12 on each side of the pylon on each side of the roadway. The distance between the cables is 12.00 meters (39.37 ft) on the main span, and 9.33 meters (30.6 ft) on the viaduct. Combined, the cables are 4,432 meters (14,541 ft) long; each cable consists of 67 to 230 twined cables, each with a 7-millimeter (0.28 in) diameter. The cables have a weight of between 1.5 and 14.5 tonnes (1.5 and 14.3 long tons; 1.7 and 16.0 short tons) each, and they have a capacity of between 1,960 and 7,910 kilonewtons (440,000 and 1,780,000 lbf). They can be tightened at the connection with the roadwall.
The floating section consists of a steel box girder placed on top of ten floating pontoons. The pontoon section is anchored only at both ends, on the underwater foundation at Kauvaskallen and on Flatøy. It is fastened using flexible plate connections fastened by bolts and cables under tension. These are flexible around the horizontal axis at right angles towards the axis of the bridge, allowing for deformation caused by the tide. The fastening on Flatøy consists of a massive concrete block 22 by 20 meters (72 by 66 ft) long and 14.5 meters (48 ft) tall which was poured into a blast-out foundation pit in bedrock. Vertical pretension rock anchors have also been installed, with 12 at Klauvaskallen and 14 at Flatøy, giving 42 and 44 meganewtons (9,400,000 and 9,900,000 lbf) of support, although they were only built to increase the safety factor.
There are ten lightweight concrete pontoons, with 113.25-meter (371.6 ft) spans between them. The pontoons are between 7.0 and 8.6 meters (23.0 and 28.2 ft) in height. The draught varies between 4.3 to 5.6 meters (14 to 18 ft). Each pontoon consists of nine watertight cells which are partially filled with ballast for trim. The cells are dimensioned so two adjacent cells can fill with water without endangering the bridge.
The roadway lies on top of an orthotropic deck on a steel box girder, which is 15.9 meters (52 ft) wide, 5.50 meters (18.0 ft) tall and 1,246 meters (4,088 ft) long. The steel box girder weighs 14,150 tonnes (13,930 long tons; 15,600 short tons), of which 3,000 tonnes (3,000 long tons; 3,300 short tons) is high-strength low-alloy steel. The girder has an octagonal shape and is made with 14-to-20-millimeter (0.55 to 0.79 in) thick steel plates. They are longitudinally stiffened by trapezoidal stiffeners supported by cross frames at most every 4.5 meters (15 ft). Two full bulkheads have been used for every pontoon pilaster, made from welded steel plates 8 to 50 millimeters (0.31 to 2.0 in) thick. External brackets built into the bulkheads transfer the support forces to the pontoons. The girder was built in sections of 21, 36, and 42 meters (69, 118, and 138 ft), which were subsequently welded together into 11 modules with a skew angle of 1.2 to 1.3 degrees. The girder has a constant cross-section throughout the length, except at the anchoring points to the pontoons. The section from the land anchoring to the first pontoon is subject to the most stress, and is made with steel with a higher yield point. The inside of the girder has two dehumidifiers which ensure that it does not rust. The clearance under the girder is 5.5 meters (18 ft).
The two bridges are connected with a 414.5-meter (1,360 ft) long steel viaduct, which runs on top of the floating bridge, bringing the road from 11.0 to 34.4 meters (36.1 to 112.9 ft) above mean sea level. The viaduct weighs 1,600 tonnes (1,600 long tons; 1,800 short tons) and has a gradient of 5.7 degrees. It consists of spans between 18 and 33 meters (59 and 108 ft), with the roadway also built as an orthotropic deck with 12-millimeter (0.47 in) thick plates. Overall, the construction of the bridge used 24,000 tonnes (24,000 long tons; 26,000 short tons) of concrete, of which 10,000 tonnes (9,800 long tons; 11,000 short tons) in the pontoons. The bridge was coated with 40,000 litres (8,800 imp gal; 11,000 US gal) of paint.
The bridge is monitored by 132 sensors, including sensors on hatches to the pontoons, on doors to the steel box girder, for corrosion, strain gauges on the girder and on flexible elements, and weather information. On the cable-stayed section, the bridge is marked with navigation lights, as well as the center of the sailing area having a racon. The bridge is the second-longest bridge in Norway, behind the Drammen Bridge.
Read more about this topic: Nordhordland Bridge