How does that not fall?

This is question I've been wondering for a while, I asked one engineer and he wasn't sure how the structure stayed up. In the City of Calgary in Alberta Canada, there is a system called the C-Train "Subway system above ground" and there are many of these Spiral Platforms with stairs on the otherside that go up to make an overp to get onto the C-Train. Now the Spiral Ramp that goes up for the handi-cap and bikers, rollerbladers and skateboarders etc, how does it stay standing? when its made of Cement and has over 1000 people walking on it all the time during the day. There is only 4 cement beams on the inside of spiral ramp that the ramp is attached to, and the ramp is made of cement. And possibly rods, inside the the spiral ramp that are attached to the beams. May be a simple explaination to this, but I don't understand how the rods support a spiral staircase made of cement that goes up over 20 feet.