For the benefit of idiotic conspiracy theorists: If memory serves, this building, unlike the Twin Towers, is of steel frame construction, but only the upper half. The lower part is, again if memory serves, made of reinforced concrete. I may err, however, so dumb conspiracy theorists go read Wikipedia, if you know how to read.
I imagine the main reason we are seeing longer bridge spans being made of reinforced concrete these days is due to the same advances in concrete technology that make it possible to build a supertall building from it. In some ways it is a shame, although a lot of truss bridges are damn ugly.