A Saudi engineer is reported to have said that the crane collapse which killed 107-worshippers in Mecca was an “act of god.”
Mecca: The collapse of a construction crane that killed 107 people at Mecca`s Grand Mosque was “an act of God” and not due to a technical fault, an engineer for the developer said Saturday.
The massive red and white crane, which crashed into the court of the mosque during a rainstorm and high winds Friday, also injured around 200 people.
Since it is hardly possible that a thorough forensic examination has been conducted, we can dismiss the remark out-of-hand as posturing. This wouldn’t be a bad time, though, to review the language with which we discuss these sorts of things.
Generally, for starters, engineers do not design against an imaginary “worst case scenario;” engineers design against the worst realistic loads as established by experience. I studied engineering in an area which routinely receives more than 200-inches of snow per year, for example, but engineers do not design roofs to support 16-feet of snow; after all, the storms which deliver all that snow are ordinarily accompanied by strong winds which blow the snow off the roof, and designing a roof which can carry that much snow would be prohibitively expensive and unnecessary.
Local building codes, based upon experience, establish how much snow the roofs must be designed to carry. So, too, wind loads. I don’t have the slightest idea what the Saudi building code calls for but, since other cranes in the area weathered the storm without incident, I doubt that the winds experienced during the storm were so freakish and unexpected that they could rightly be characterized as an “act of god.”
Second, as used by engineers, the word ‘failure’ has a very narrow meaning — that something did not perform as designed. The iconic example is the Titanic, which sank catastrophically but did not ‘fail’ because it wasn’t designed to survive a collision with an iceberg. So, too, the crane; it may have collapsed, but it ‘failed’ only if it was loaded by winds within the design range. Since Mecca is in the midst of a building boom and only one crane of dozens collapsed, I think it is quite likely that the loads were within design range and that its collapse was indeed a failure.
It is much too soon for a proper forensic examination to be complete, so all we can or should say at the moment is that we don’t know why the crane collapsed. Experience suggests the place to begin looking for a cause, however, is corrosion or fatigue at connections. That’s certainly the danger in America’s neglected infrastructure.