I don't know if there are any structural engineers on this board but I thought I'd ask opinions about something that has peaked my curiosity. Across the street from me, there is multi-level building being constructed and currently its on about the 15th floor. Nothing unusual about that in NYC except that every building that size that I've ever seen built has had a steel frame--a structure of I-beams that are riveted together around and upon which the walls and floors are installed. This building has no steel frame. What they been doing instead is using steel rebar and pouring concrete over it. Rinse and repeat for every floor. I've honestly never seen such a tall building being constructed this way and it doesn't strike me as terribly stable. I guess we aren't going to get any earthquakes in NYC but still.