How can I skip local cable modes in modal analysis of a cable-stayed bridge?

You should be able to eliminate these local cable modes by using one of the following approaches:

Define the cables using only one segment. Then the cable mass will be distributed only to the start and end joints of the cable and therefore local cable vibration should not get excited.
Keep multiple cable segment, but assign model the cables as massless. This could be done either by assigning zero mass modifiers for all cables (via " Assign > Cable > Property Modifiers") or by changing the mass for the cable material to zero. Please note that this approach will somewhat underestimate the total mass of the structure.
Run modal analysis based on Ritz Vectors rather than on Eigen Vectors. Specify Ritz Vectors that will excite the global modes of the structure.

How can I consider the various loads that are applied to cable stayed-bridges?