Bridges

The Bridge over Cooks River at Tempe was built in 1960 and designed to carry HS-20 loading. The bridge is on the Princes Highway, a major heavy vehicle route in Sydney. The bridge is currently carrying six marked traffic lanes and with high traffic volume includes Semi-Trailer (ST 42.5) and B-Double (BD 62.5) vehicles. The bridge is located in an aggressive environment which resulted in severe deterioration of existing piles of two pier substructure. Bridge rehabilitation design and construction work were carried out to restore bridge load carrying capacity, minimise disruption on traffic and address safety risks.

Stage 1 Bridge Rehabilitation:

Substructure strengthening was carried out in 2004 by constructing additional cast-in-place bored piles adjacent to existing pier substructure. The strengthening work adopted innovative underpinning system solution through external steelworks and vertical prestressing hanger bars to jack up the entire pier substructure in order to transfer loads to the new piles. An impressed current cathodic protection (ICCP) system was installed to provide corrosion protection to the piles and yoke beams on Piers 1 and 2 below mid-tide level.

Stage 2 Bridge Rehabilitation:

Encapsulation of Stage 1 external steelwork through construction of new concrete pile cap in 2015 and installation of cathodic protection system in 2016. The prestressed concrete pile cap was designed using strut and tie method to "pick-up" bridge load through upward hogging moment introduced by eccentric prestressing effect. The solution achieved concrete to concrete integral connection between existing pier substructure, Stage 1 piles and Stage 2 pile cap.

This paper outlines:

1. Project challenges
2. Rehabilitation solutions
3. Construction challenges
4. Cathodic protection