huangyhg

structural damage from hurricane katrina
the american wood council issued a six page report today (october 7) summarizing certain aspects of residential damage from katrina (it is kind of an infomercial, but still worthwhile). i don't see it posted on the web, so have put it on my site (first item on home page, see link below). will leave it there for a few days.
reading the report, this is exactly was happened with ivan.
in reality they were finding so many violations of the building codes, the one that existed at the time of construction, that they quite looking when the fingers started moving.
taking out the surge damaged areas the worst damage was in houses that weren't tied to gather. as an acquaintance put it, "the hurricane clip by itself isn't worth jack crap". the roofs decked with 3/8" thick material nearly all failed for essentially the same reason. even where the nails hit the truss the nails pulled through. another prominent failure was where the bottom plate was shot in instead of anchored with anchor bolts, the whole house moved or the wall caved in. another prominent failure was with metal roofs peeling off the roof decking. the battens were just nailed in the decking and no effort was made to hit the truss. the result was that the whole thing peeled up, the metal roof still attached to the battens.
the jest of it is that you can take some wind without structural damage if the proper design elements are called out and you get a first class construction job that uses the elements.
what i'd like to know is, what has been the civil/structural engineering community's response in the immediate aftermath of these disasters? has it been adequate?
i was in new orleans for 3 weeks assisting search and rescue operations, particularly for identifying collapse hazards for the search teams. we were somewhat restricted in the areas we could operate in. i mostly was kept busy in the flooded areas. we saw some structures adjacent to the breeches in the levies that were displaced from direct water flooding impact forces. these had been displaced off their foundations. once the water level went down and we could perform some inspections, it was apparent that generally speaking the floor systems were not very well connected to their support piers. it would not have taken much force to move them off. these piers appeared to be about 30 inches in height, and spaced approximately on 12 ft + centers. this formed open spaces under the structures, that the flood waters readily entered into. most of the flooded structures i was able to inspect did not, however, displace off their foundations. i did, however, hear that a number of structures started to collapse in other locations once the waters receded. i could not, however, inspect those locations and identify the causative factors. i did see some structures that collapsed presumably from wind forces. these, however, upon closer inspection appeared to me to have probably been of questionable integrity prior to the hurricanes. they were older, had extensive termite damage, and just marginal integrity. the flood waters typically saturated the interiors of the structures and virtually all the wall and ceiling coverings had fallen off. the framing, however, in general, remained intact without localized collapse. the 'storm surge' areas were a sight to behold. i witnessed boats with their trailers still attached placed of the top of roofs, along with dumpsters and heavy planters. it appeared that the construction in these storm surge areas was newer and of reasonable integrity. most had external brick veneers that remained intact and attached to the wall framing, although the buildings had been fully submerged during the surge event. with the exception of a few, unanchored 'add-on' carports and storage buildings, no collapses were noted in general. presumably the storm surge came in fast enough to trap people in their attic spaces, but none of the main structural framing in these areas had been displaced. i was surprised to see that some of the attic spaces were able to hold enough air to allow people some safe havens although the water outside their homes appeared to have been above the roof lines. other areas of the city i looked at where flooding had not occurred appeared to be in reasonably good condition. loyola university structures showed no evidence of distress except to loss of roofing material in certain locations. although i wasn't allowed direct access in, some 14+ story medium rise structures appeared to have come through the event with the loss of glazing at the building corners. i noted the complete collapse of what appeared to be an open, braced (?) steel parking structure in the area of the airport. i wasn't, however, allowed access for inspections. there was so much mold and bio-toxic residue inside all the flooded structures we inspected, that we had to be decontaminated at the end of each work day. it took we a good 10 days to get over various rashes and respiratory infections i picked up while on deployment there, inspite of the protective gear i wore.

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