The column bay is 30? by 45?, with owsj spanning 45? at 15? on center. Thus the 8? concrete slab spans 15?, with the 3? decking running perpendicular to the joists, for structural reason, but has the additional benefit of allowing wiring to be run the length of the building to the vertical service shafts located at both ends. The hallway ceiling and floor serves as the main horizontal distribution.