The Second Severn Crossing

 Sarah M and Simone S,      Year 8

 The Second Severn Crossing was constructed at over 3 miles long and within sight of the first Severn Crossing. The Second Severn Crossing was built over the main part of the River Severn’s Tidal Estuary.

The John Lange Corporation constructed the project.

The Exposed location of the bridge means it needs to be strong to put up with the very strong winds that blow up the Severn estuary from the sea, and not be an eyesore.

One of the main features of the bridge is the 465 m span cable-stayed bridge that spans the main navigational channel. The two pylons are made from 150 m of concrete they resemble two high-jump bars, the cross beams came ready made, 240 stay cables were also used, on both sides of the cable-stayed bridge.  The 2300 match-cast units that form two viaducts are pre-stressed for strength.

Strong winds were not the only problems faced by the construction team the also had to face 14.5 m tidal range which is why most of the concrete was pre-cast on shore. The concrete was then transported onto the estuary by specially made equipment. The design and build contract meant that the construction methods were considered at the early stages of design.

The piers were formed using hollow rectangular units so it was a quicker construction.

This is the first bridge in the UK where external and internal tendons have been protected by wax filled ducts for durability and ease of replacement.

The project demonstrates that extensive use of large-scale pre-casting

The Second Severn Crossing is an amazing engineering feat and a vital transport link that was completed, in spite of great difficulties and challenges posed by the site, to budget and on time.