Why do the cables of cable-stayed bridges all look the same thickness?

1. What you see on the outer surface of the stay cable is only the PE protective sleeve covering it; the dimensions are similar, so they appear to be the same thickness. In reality, a single stay cable is made up of many steel wires or strands bundled together. Generally, a cable-stayed bridge has at least three types of stay cables, and large bridges may have even more.

2. Asymmetry in the angle and number of stay cables is not a problem. Cable-stayed bridges are not passively sag and hold the main beam in the common perception; instead, the tension of each stay cable can be actively adjusted, like a jack pulling at any desired force. Therefore, even if the cables are asymmetrical, the force can still be symmetrical. (As an aside, a symmetrical single-tower cable-stayed bridge is actually not a good structure; without the denser anchor cables at the anchor span ends, the overall system stiffness will be lower.)

3. In terms of the main beam material: concrete is more economical for short-span cable-stayed suspension bridges, composite beams are more economical for medium-span bridges, and steel is more economical for large-span bridges. In terms of the tower material: concrete bridge towers are more suitable for vertical bridge towers that are primarily subjected to compression, while steel bridge towers are suitable for complex shapes that are curved or inclined. In fact, there are quite a few steel cable-stayed bridges and suspension bridges, but due to historical habits and cost reasons, my country does indeed prioritize the use of concrete structures.