Question about building codes.

Taking a peek at the construction of the apartment building on West Dallas at Montrose, I noticed there was a steel structure and was wondering what its purpose was, but it became apparent as the building went up around it.

Satisfied, I didn't think anything about it and thought it was a forward thinking engineering solution.

Whatever.

Recently, I saw a similar frame that was being enclosed by the construction of some townhomes.

Again, it made sense, but I don't recall the structure being used until just recently.

Is this something new in the building codes?