CONSTRUCTION OF a new 8.6km long, £436M road bridge in New Orleans began last week, to replace a viaduct badly damaged during Hurricane Katrina.
The bridge is understood to be the most expensive public infrastructure project in Louisiana's history and is being paid for by the US Federal Government.
It replaces the existing Interstate 10 bridge (I-10) that crosses Lake Pontchartrain and links the states of Louisiana and Mississippi. It lost 64 of its 866 concrete spans in the storm surge that swept across the lake (NCE 8 September 2005).
The new bridge is to be built on the eastern side of the old bridge and stands 9m above water level, 6m higher than the previous structure. It will carry three lanes of traffic in both directions (instead of its twolane predecessor) and use a less permeable, higher-strength concrete mix.
'The bridge has been raised so much that we don't foresee getting any water [hitting the deck], ' said Louisiana Department of Transportation & Development project manager Arthur D'Andrea.
Designers have also minimised the risk of sections being washed away by increasing the weight of each segment and tying them together. 'Six spans at a time are connected. So to knock one span out of place the water would need the force to move six, ' said D'Andrea.
At up to 1,000t each, the concrete deck segments weigh almost four times more than those of the earlier structure.
Lateral restraint will be provided by lugs on transverse supporting beams, between which the deck's longitudinal beams will sit.
Constructor Boh Brothers will build the new structure under a five-year contract. Until it is completed commuters to New Orleans will use its predecessor, which was repaired and fully reopened in January.