As I was taking photos of the new Le Meridien / AC tower crane, I noticed something new on the 1144 Fifteenth site. The core is starting to rise out of the hole!
High-rise construction methods vary from project to project. Seeing how 1144 Fifteenth is rising, I am guessing the core will go up first, with the main structure following behind; similar to what we saw with the Triangle Building. This is also a very common practice for steel builds, which will be the primary structural material for the 40-story tower. Here are two photos, from a few blocks away, showing the rising core.
This will definitely be an exciting project to watch in the coming months!