The world’s longest suspension bridge could easily be built if its cables were made from bundles of carbon nanotubes, say Alberto Carpinteri and Nicola Pugno from the Polytechnic University of Turin.

The thinking for this rather unsurprising news is that carbon nanotube cables would allow the main span of a suspension bridge to increase in length by a factor of three, to more than 6 km.

The motivation for this analysis appears to be the problem of building a bridge across the Strait of Messina, the water that separates Sicily from mainland Italy and which would require a main span of some 3 km.

But  a little more interesting is a corollary in which the authors have analysed the length of the record setting suspension bridges built since the Brooklyn Bridge in 1883.

Carpinteri and Pugno say they’ve found a Moore-like exponential relationship. That’s kinda interesting (even if the exponent is only 1.0138) because we usually associate exponential increases with hi-tech industries.

Carpinteri and Pugno says the bridge could be built now with carbon nanotube bundle technology. The bad news, however, is that by extrapolating along this curve, it’s clear the Messina Bridge will not be built until about 2050. Probably with carbon nanotube bundle cables.

Their’s is clearly the triumph of hope over extrapolation.

Ref: arxiv.org/abs/0804.1446: Super-bridges Suspended over Carbon Nanotube Cables

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