A portion of a garage collapsed in Atlanta yesterday. This happens extremely seldom. John Clancy wrote to me that he wondered about whether the installation of loop detectors for a revenue control or counting system may have nicked a post tension cable. Who knows? Lack of facts never stopped me, soI will comment.
In a past life I was involved in installing loop detectors in post tension garages. The urban legend was that if the cable was nicked by the saw cutting the loop the cable would break, leap out of the floor like an angry cobra and cut anything in its path in two (cars, people, whatever). I never saw this happen but know people who swear they have.
I understand that in the past decade or so they have encased the post tension cables in a plastic sleeve so if they do break, they will contract in the sleeve and not come ripping up out of the floor. Perhaps one of the tech weenies out there could confirm or deny.
When we installed loops for either gates or counting in post tension garages, we had to locate the cables so we wouldn't cut them with the saw. There were numerous devices out there to do so, but often we had to call in the experts who used magnetic imaging to find the cables and tell us where we could cut.
Take a look here at the pictures of the collapse. I can't tell for sure, but this doesn't look like a post tension garage to me. Any experts out there?
JVH
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