I’m sure if other bridge designs (suspension, truss, etc.) could safely have just a central support, they would, as it would cut down material costs by a lot, but, it seems basically only cable-stayed bridges sometimes have this design. Googling various versions of the question, I couldn’t even find some sort of advanced engineering explanation of the forces, nonetheless something I could understand. Hopefully one of you can?
In: Engineering
A suspension bridge have a single or pair of wires that hold up all of the bridge deck. It is under load even when the bridge deck i not installed and then the load changes during construction. When there is a load on one part like a heavy truck result in the wire slightly change position, So the bridge decks need to be relatively flexible
In cable stay bride there are multiple wires that work independently, which mean there is less motion. The force on the bridge segment is alos not vertical like in a suspension bride but has a horizontal part too. So the bridge segment needs to be stronger to handle horizontal compression, in a suspension bridge segment can hand independently from the vertical wires and there is no horizontal force in the bridge
The result is the cable stay bride can be stong enough so the bride deck can handle twisting forces without adding a lot of material. In a suspension bridge that can have a lighter deck its tickets and the lack of horizontal compression on the bridge result is that they would twist more if there only was a single wire support.
In general the same material can do more works the farther it is away from the center. So a truss bride likely use less material if you haver steel on both side compare to just in the middle. It alos make the road part simpler with a single open span.
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