A composite view of the tower model, the tower during construction, and the tower on the completed bridge. I imagine the back bearings are in tension and the front bearing is in compression to resist the overturning force of the cables pulling on the tower. However, it's possible that since the tower leans backward and has such a heavy base that all three bearings stay in compression (and shear). Also the large tower base can resist the bending and shear from the cables pulling on the tower.
The cables are in a harp-arrangement. They are attached to steel arms on the side of the tower and to the vertical elements in the superstructure segments. They call this kind of bridge a 'cantilever spar' to differentiate it from cable-stayed bridges that support the superstructure by balancing the load on each side of the tower.
Note the vertical slots along the edge of the tower. Its possible they have a structural function, but I doubt it. They look more like ornamentation, like the openings they used to put in the sides of a Buick. Also, the glass deck looks nice on the bridge. However, at first, the tiles were prone to shattering whenever a hard object was accidentally dropped on them.
The tower points north and is used as a sundial in the park surrounding the bridge. The shadow moves fast enough so that you can perceive the Earth spinning on it's axis.
Cable-Stayed Bridges - Sundial Bridge (5) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.