An earthquake-damaged bridge in the New Zealand city of Christchurch is to be raised using heavy-lifting techniques, allowing the next stage of repairs to take place.
The 38-year-old Durham Street Bridge – which is one of the busiest in the city - sustained significant damage in the Canterbury earthquakes of 2010 and 2011, leaving the reinforced concrete beams and the pier heads cracked and crumbling.
The raising of the 5,000t bridge will enable specialist teams to begin the next stage of repairs, due for completion in August next year. The operation follows an initial three months of preparatory repair work by the Stronger Christchurch Infrastructure Rebuild Team (SCIRT).
SCIRT executive general manager Ian Campbell said: “Although the bridge is perfectly safe to drive on at present, it is vital SCIRT completes repairs to the over-bridge for its long-term future.”
Up to 28 hydraulic jacks are being used to lift the bridge by 10mm over four hours so that the weight comes off the pier heads while they are being repaired.
"It is a precise process that requires all the jacks to work in unison,” said SCIRT Fulton Hogan site manager Paul Thornton.
Hydro-demolition techniques will then be used to blast away the old, damaged concrete from each pier head, exposing the steel reinforcement ready for new concrete to be placed.
The pier heads are being repaired one by one over the next 10 months. There will be up to 18 night closures during the project to allow the lifts to take place but the bridge will otherwise remain open. The deck will be raised off the jacks for the first time tomorrow night (25 November) and the second lift is on Thursday night.
More than 11,000 cars use the popular bridge every day. Repairs to Durham Street Bridge are expected to cost US$1.5 million and are co-funded by the New Zealand Government and Christchurch City Council.
