[Nowhereman1280]

Just look at the building again for a second and ask that question once more. Do you really think those floorplates are just holding themselves up?

Yes those are load bearing arches and the striation patterns do not mean they aren't. In fact, all concrete in all buildings has that pattern because it is nearly impossible to pour concrete on an angle without horizontal striation patterns since it would just flow out of the forms if they were on an angle. I believe the concrete on Prentice is only half the story structurally. I believe there is a large curving I-Beam inside the bottoms of those arches just like the bottoms of the balconies at Marina City that ties the whole thing together. I'm not certain though and this could easily be verified as there are construction pictures around the internet somewhere.