Vertical cables in a suspension bridge

[OmegaKV]

Homework Statement

Problem 5 here:

http://www.princeton.edu/~romalis/PHYS203/HW1.pdf

Homework Equations

N/A

The Attempt at a Solution

The part that really confuses me is where it says that the cable lengths are adjusted so there is no shear stress on the bridge. What exactly does this mean? Does that mean the cables are loose enough that there is no tension in the cables? If that's the case, then what difference do the cables make?

 

[mfb]

Does that mean the cables are loose enough that there is no tension in the cables?

No, it means there are no horizontal forces on the bridge elements. If the cables would have lengths not matching the bridge structure you would get this.