19 June 2014

Australian Bridges: 1. Sea Cliff Bridge

I spent some time in Australia a few months ago, and while I didn't get time to visit many bridges, I did see a couple which are worth featuring here.

The Sea Cliff Bridge is on the coast of New South Wales, north of Wollongong. It was built in 2005 to replace a section of highway repeatedly affected by landslides and rockfalls. The bridge is 665m long, and represents a significant engineering achievement, not only for having been built at such an exposed location.

The southernmost section of the bridge is in the form of a post-tensioned balanced cantilever bridge, with 108m main spans. This is built on a varying curve in plan, meaning that every 5m long concrete box segment was different in curvature, angles, as well as in depth, with the spans varying from 6m deep over the piers to 2.5m at midspan.

The northern section of the bridge, approximately 200m long, has much shorter spans of 30m, and a constantly curved radius in plan of 150m. The form of the deck is different, comprising twin curved concrete beams, of constant depth, matching the depth of the balanced cantilever bridge where they join so that in elevation they appear to be continuous structure. The north part of the bridge was installed by incremental launching.

The combination of the two construction methodologies is unusual, and I'm impressed by the careful construction control that will have been required.

Despite the spectacular setting, the bridge is not especially exciting to drive over, as views off the highway are largely obscured by precast concrete barriers. It is better appreciated by walking down to the shoreline below. As well as the bridge itself, there are some impressively eroded rocks to see.

Further information:


Paul Mullins said...

The bridge was designed by Maunsell (not long before becoming AECOM) and back in those days the project was called the Lawrence Hargrave Drive. I was doing a stint with Maunsell in Sydney while it was being designed but was not part of the project team unfortunately, it was a very challenging project from what I can remember.

You've been a bit slack on deriding architects and silly design competition entrants of late. It always makes for very good reading!

The Happy Pontist said...

Sadly I am still extremely busy with work, but I am trying to get a bit more time to post on here. I have a backlog of bridge visits to cover, so those will take priority until I get through them.