Skyscraper at Trade Center Rises From the Inside Out

If you think Santiago Calatrava’s transportation hub and shopping mall looks like a bird (or a stegosaurus), you might find 3 World Trade Center next door reminding you of an upside-down Popsicle, with the stick at the top…

Such buildings — concrete cores and steel perimeters — are called “composite” or “mixed” structures, said William F. Baker, a prominent engineer and partner in the Chicago office of Skidmore, Owings & Merrill.

“The first examples I knew about were in Chicago in the mid-1980s,” he said. “I have seen this system all over the world: London, Shanghai, Seoul, Dubai, Beijing, Kuala Lumpur, et cetera. New York is one of the last places to adopt it.”