UPDATE Sept 2011: This letter was followed by two more from Dr Bisby and Hilditch
UPDATE Dec 2011: The letter of Dr Bisby has been published in the December 2011 issue of Scientific American.
(email sent on Thur 15 Sep 2011 to email@example.com)Dear Editor of Scientific American,
Your September issue included the piece "Castles in the Air" by Mark Lamster where the failed prophecy that the attacks of 9/11 were to end the age of the skyscraper is discussed. The article highlights that 2011 will be the single greatest year for the construction of tall buildings in history. That China is leading the skyscraper boom, yet their engineering design is dominated by American firms.
The article discusses design issues on evacuation. But the World Trade Center was designed to evacuate rapidly, and so both towers WTC1 and 2 did below the impact floors on 9/11. WTC7 was also evacuated in time.
The article also discusses design issues on aircraft impact. But the World Trade Center was designed to withstand the impact of a large aircraft, and so both towers WTC1 and 2 did on 9/11. They collapsed because of fire. WTC7 was not hit by an aircraft, but collapsed due to fire as well.
The article goes to imply that the design of tall buildings for protection against terrorist attacks is mostly about aircraft impact and evacuation. It does not discuses fire. But WTC 1, 2 and 7 collapsed because of fire.
So they only issue that is not addressed in the article is the one that brought World Trade Center down, and the one where design advances over the past decade have been most marginal. This is a thin favour to fire engineering and to the safety of tall buildings.
Dr Guillermo Rein
Senior Lecturer in Mechanical Engineering
University of Edinburgh
"so easy it seemed, Once found, which yet unfounded most would have thought, Impossible!" J Milton