Very little real information can be drawn for New Orleans because of the quality of construction, the rise was gradual and may not have been classified as a "surge", but just a rise. If it is a gradual river flooding the current and associated forces can be estimated using approximations. The major frequent storm surges and flood levels are not adequate for some typical surges to determine a structural analysis. Your estimated factor comparing a storm surge in comparison to wind may be realistic for small, slow surges. This system was used on many during the early rebuilding. The temporary/sacrificial blow-out walls (perpendicular to the coastline) were generally 6" CMUs (virtually unreinforced) and just were used for general protection and enclosure of lower bathrooms/showers, utility rooms, garages, dens, TV rooms and workshops. The other structures that survived were the elevated homes with a rigid concrete frame on deep spread footings or reinforced CMU columns with designe "blow-out walls". The reinforced concrete homes with a good foundation survived well and were habitable or cleaned up within a few days if you could get to them. This was a situation were the surges were generally perpendicular (within 30 degrees) to the coast line and normal tracks for most storms.Īnything with either steel, timber or concrete piles under an elevated home was gone and there where few blow-out walls that were in evidence after the surges. The most severe conditions for storm surge were on the Mississippi coast there there was a 28' or so surge and and and equally damaging outward surge because of the debris. Had it broken-away as designed, there likely wouldn’t have been any damage to the livable area of this building.Just after and later in Katrina country, after looking at the damage and typical failures, I can only offer observations and not too much in specifics. A large obstruction can be seen behind the wall, preventing it from breaking-away. The window was smashed and flood waters rushed inside. When this wall failed to break-away, the wave action was deflected upwards. If designed properly, the following photograph shows how a ground floor enclosure with breakaway walls would/should look after a ravaging storm. Wooden lattice will break more readily when struck by floating debris. It won’t break, and will collect a large amount of debris causing the wave action force to be transmitted to the entire building.
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