Bridges

The Southbound Swansea Bridge, constructed circa 1989, is a high profile bridge on the Pacific Highway at Swansea, NSW. Due to harsh marine exposure, the bridge substructure elements have suffered from reinforcement corrosion. The bridge has an opening span for large boats to pass through.

Cathodic protection (CP), a state of the art technique utilising DC electric current to combat reinforcement corrosion, was selected to provide increased durability and service life to the Bridge.

Selection of the CP option was made through a systematic process involving:

• Undertaking specialised condition investigation using state of the art computerised modelling to assess current deterioration and progression of damage with time.
• Assessment of feasible, cost effective long term options.
• Consideration of the likely community impacts associated with certain options
• Assessment and maximising of the CP system and components for a design life exceeding 50 years
• A detailed, innovative and unique study to determine the effects of CP on the marine flora and fauna.

As this was a highly complex structure and one of the few CP installations on an opening bridge, the many engineering challenges were overcome by utilising sound and innovative engineering practice principles. As such, a range of CP techniques had to be used to ensure full corrosion protection, including: silane coating application, impressed current CP, sacrificial anode CP for above water elements, and sacrificial block anodes for the below-water elements.

Through the collaborative approach taken by the three organisations (GHD, RTA, and Marine & Civil Maintenance), and the excellent final result, this project received a Highly Commended award from Engineers Australia Sydney Division in 2010.