http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.htmlChangleen said:WTCs had a central core of services and and outer shell providing support. The floors were apparantly 'hung' between these two load bearing features.
More engineers...
edit: I made a mistake between gravity load and wind load, btw. Sorry about that. I'm NOT an engineer.