Also covered by 99% Invisible, which has a nice postscript to the linked story.<p><a href="http:&#x2F;&#x2F;99percentinvisible.org&#x2F;episode&#x2F;structural-integrity&#x2F;" rel="nofollow">http:&#x2F;&#x2F;99percentinvisible.org&#x2F;episode&#x2F;structural-integrity&#x2F;</a>