Nerlandsøybrua (case study)

Nerlandsøybrua is a coastal bridge in Herøy, Møre og Romsdal. It is rather slender construction built in 1967. The 404 m long beam-plate bridge consists of 20 spans, a T-shaped cross section, and rectangular shaped columns with varying height. The 40 m long main span and the two adjacent spans are prestressed, while the remaining spans are ordinary reinforced. As result of a less strict set of rules of design, concerning environmental threats at the time of construction, the Nerlandsøya Bridge is not armed for the rough climate at the coast of Sunnmøre. In the 1990s, the bridge was installed with a cathodic protection system.

Object description

(No object description available.)

Civil engineering type

:

Road network Bridge

Year of construction

:

1966

Composed of materials

:

Prestressed concrete, Reinforced concrete

Location coordinates

:

62° 20' 24.32" N, 5° 36' 21.67" E

Country

:

Norway

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Object analysis

Capacity Control of the bridge’s superstructure and the most critical column is performed at ultimate limit state. The framework program NovaFrame is used for the modeling of the bridge to determine the design forces. Håndbok 238 is the basis for control of loads and NS3473 Concrete structures - Design and detailing rules is used in capacity calculations.

Case type

:

Other

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Object state

During this inspection there were studies conducted on the materials where the concrete cover, carbonation and chloride content was measured. The chloride content proved to be of critical value in several places on the bridge. This indicates that chloride corrosion is likely. The largest values for chloride were registered on the north side of the bridge, sheltered from the design direction. The areas closest to the land had the highest chloride content, which is expected because of the low altitude. Visual inspection of the damages coincided well with the chloride studies. In areas with high chloride content there was also detected spalling and delamination of the concrete cover. In areas where the reinforcement is visible there is obvious corrosion.

Observed deterioration processes

:

Chloride induced corrosion

Observed damage types

:

Spalling, Local rupture or failure, Material loss of reinforcement steel, Cracks, Delamination

Performance indicators

:

Chemical properties, Spatial properties (concrete cover/duct voids)

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