Widening of the bridge over the Rande Strait

The Bridge over the Rande Strait is the first long span cable-stayed bridge widened in the world, being a unique milestone in the field of Structural Engineering.

This 400m span cable-stayed bridge over the Rande Strait was opened to traffic in 1981. In
2006, the average daily traffic reached 47,000 vehicles, close to its effective capacity. In order to increase the bridge’s traffic capacity, several studies were carried out.

The most advantageous and innovative solution was a widening project consisting of two new external decks positioned along both the outer sides of the existing deck next to the main piers.

Two new groups of stays support the new decks. Due to its innovative design, the cables of the original bridge are slightly unloaded so they never exceed their previous load. The bridge was enlarged without modifying the existing foundations.

Several wind engineering studies were developed including CFD and wind tunnel model analysis. Both revealed that the bridge was not vulnerable to aeroelastic instabilities.

Its innovative design solves the functional problem proving a significant increase of the highway capacity while maximizing the use of the structural strength of the existing bridge as well as improving its dynamic behaviour. The construction was also accomplished, without affecting both the traffic and the natural environment, in a record time of 14 months for the on-site erection.

This represents a vital innovation for the world as old infrastructure faces capacity constraints.