I read the article "Engineers Caution Against Overreaction," and as a former structural engineer, I couldnt agree more with the dissenting voices (ENR 1/25 p. 10). The reasons for the collapse of the trade center towers and a portion of the Pentagon were many faceted. Not only did the buildings sustain huge loads, via impact of the airplanes, the fuel caused fire to erupt. This is a deadly combination. The 1906 earthquake in San Francisco, albeit a natural disaster, unleashed a similar terror from fires from ruptured gas lines.
We cannot base building design on extreme events, though such events cause deaths. Where does one draw the line?