3 Responses to “Petroski: Nanotech for safer skyscrapers”

1. michaell Says:
   September 27th, 2001 at 5:43 AM

   I had the same thoughts…

   When the towers collapsed I thought to myself if only they were constructed using carbon nanotubes which have 100 times the tensile strength of steel…

   However they also combust at 500C which would have ultimately made them potentially more fallable than the steel used in the WTC towers. However the use of Nanotubes may have prevented the chain reaction collapse of the 2nd tower which saw the collapse of ten floors lead to the destruction of the hundred beneath it.

   What was really needed was better fire proofing on the steel beams, the bending and buckling of which from the heat of the fires caused the collapse… It's sad to say but the fireproofing in the WTC towers was obviously inadequet, no fire should cause buildings to collapse that quickly. The use of ceramic fire proofing on the support beams may have been the building's undoing, if they had used good old fashioned asbestos which is extremely plyable they may have withstood the fires a little better… there again they you may have just ended up coating Manhatten with asbestos dust… who's to say.

2. RobertBradbury Says:
   October 27th, 2001 at 11:15 AM

   Building safer skyscrapers

   My ideas

   • In terms of Young's Modulus, diamond is ~5.3 times stronger than steel, while sapphire is only ~2.7 times stronger. Steel has a melting point from from 1650-1800K, depending on the carbon content. It begins to lose strength from 1150-1350K. So while sapphire doesn't have the strength to weight ratio of diamond, its melting point (2345K) is much greater than diamond (which different sources list as melting from 1275-1800K). Using sapphire for the structural members it is likely to be able to withstand the temperatures of a fuel based fire. It could be reinforced with buckytube or boron nitride nanotube cables if you wanted to make it stronger and more fracture resistant. If you wanted to be really sophisticated, you could pump cooling fluid through the nanotubes to keep the material temperatures below those where they begin to lose strength.
   • Coat essential supporting beams in TiC (MP: 3413K), preferably as an aerogel or even better a gel with evacuated pockets. That would have terrible heat conduction properties and allow the building to withstand higher temperature fires (e.g. thermite bombs).
   • Make the outer support frame pillars triangular instead of rectangular. They would tend to shred incoming objects rather than give way under pressure.
   • Develop firefighting robots that can dispense fire-fighting liquids or gases while at the same time sequestering flamable liquids or gases (similar to respirocyte nanorobots).
   • Develop personal evacuation systems, perhaps semi-intelligent parachutes that could provide the complex navigational decisions required for managed descent in places like New York, or perhaps nanotube cable based systems that could be rapidly deployed outside the building and could provide hyperspeed controlled descent to the ground.

   There are probably many more applications of nanotechnology that could make skyscrapers much safer places to work or live. Much more thought needs to be devoted to the problem.

3. Steel Says:
   August 22nd, 2005 at 3:12 PM

   Actually, there are other materials available that would do the job, but they are not as cost-efficient. In the next few years, we will likely be seeing much more about poly buildings. I am sure they could make these fire resistant.

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