ArchiCAD materials simply tile a flat surface such as your deck, even if your deck is in the shape of a circle.
If you need a circular pattern, you will have to create it in Photoshop (etc) at a size that will map to cover your surface. (Alternatively, you can create a material that covers one quadrant of your circle and use the tiling/mirror method shown in the attached screenshot. This is herringbone brick from the lib, but you can see that if the image was of arcs for one quadrant of a circle, the result would be a complete circle. Personally, I'd just do the entire texture as a 1-to-1 image map in Photoshop to be sure there were no repeats.)
If I understand what you are asking...
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB