Pennsylvania roof collapses from 1980s snowstorm
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Computer-aided design that shaved safety factors via doubler-plate beams; battery plant burned to the ground, fire trucks unable to reach through six-foot snow drifts. No one hurt.
On shaving safety factors: I've mentioned roof joists a couple of times. In the mid 80s, computer programs got to the point where they could calculate the stresses, and rather than having a uniform beam, designers could put doubler plates on these things and still meet the code of 1.67 safety factor — five-thirds times the expected stresses. The problem is the computer programs couldn't deal with asymmetries in erection. They also couldn't deal with the fact that some of the joist welds might not be any good. So you get a big heavy snowstorm that exceeds the expected snow load, a number of things come together, and the roof falls in — hopefully no one's around to get hurt other than property damage.