HURRICANE WINDS topping 200km/hr have severely damaged the roof of the world's longest span steel building, the Louisiana Superdome, according to reports from New Orleans this week.
The final death toll in the US Gulf Coast states from Hurricane Katrina was still unclear as NCE went to press, but at least 50 are said to have died in Mississippi and Louisiana. Up to 10,000 of New Orleans' most vulnerable citizens took refuge in the 1970s-built Superdome, a steel framed structure with a main clear span of 205m which is home to both American football and baseball teams.
When built in 1975 the roof cladding was made of ribbed steel decking topped with 25mm of polyurethane and a spray applied chlorosulphonated polyethylene waterproof membrane. During the peak of the storm, however, the roof is reported to have failed around an area of vents. Two holes up to 7m long and 3m wide opened up, allowing rain to drench those sheltering below.
Further damage followed, but the operators of the Superdome are convinced there has been no structural damage to the massive steel trusses that span the arena below.
Elsewhere, a 70m section of a city centre levee is said to have collapsed, allowing the storm surge to pour into the city. Both airports were under water, and New Orleans mayor Ray Nagin warned there would be no electricity in the city for four to six weeks.