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8 May 2001 |
Bridge Final Span Soon In Place
The new bridge over the Avon River will soon be in place and officially opened in a few months.
The third and final span of the bridge that is part of the Woolston-Burwood Expressway will be put in place during the week starting Monday 14 May.
The finishing of the 50m-long bridge, four lanes in three spans, is running parallel with the completion of the road works that include the section to the New Brighton Road roundabout and the section from the New Brighton Road roundabout through to Wainoni Road. The official opening of this stage of the joint Christchurch City Council-Transit NZ-$16 million expressway is likely to be in mid-August. The next stage from Eureka Street to Birch Street is being designed at present and will be constructed next year. The new bridge is no ordinary bridge with many unusual characteristics. One is that it has been designed to meet earthquake liquefaction problems and others include special pier frames to enhance its appearance, caissons specially designed to resist seismic forces and cycle-pedestrian ways built partly below the tide level. The two-pier frames that support the bridge deck are also unusual in that they are made from pre-cast elements bolted together using innovative steel knee joints. When construction started with the driving of the pier-frame support caissons it was found that ancient totara logs blocked progress. The original site investigation did not show the timber, says the City Council’s structural engineer, Lloyd Greenfield. The timber was smashed through eventually but the vibration from this set off ground liquefaction that led to lateral spreading of the riverbanks. This pushed the top of the caissons in towards the river. The bridge is designed to cope with liquefaction but the lateral spreading caused by the vibration during construction was new problem for the engineers. The cycleway underpasses partly descend below water level and special jointing and sealing systems are used to maintain water tightness. The underpass foundations are different, too, as they are designed to resist uplift from flotation and to support the full weight of the water should the underpasses become inundated and the tide then recede below the base. The first stage of the Expressway - Anzac Drive - has been open since last August. The final stage from Eureka Street to Birch Street is being designed at present and will be constructed next year. Eventually the expressway will be handed over to Transit NZ as a state highway, says the City Council project manager, Jeanette Ward.
Further information: Lloyd Greenfield, City Council’s City Solutions: 9418 756.