Code for Cable-stayed Bridge

I would think that there would be an AASHTO specification/code for that. Have you tried AASHTO?

I am thinking there might be an AASHTO guide spec. But just can not find.

AASHTO, with a grain of salt.

Certain components would be designed using AASHTO - stringers, floorbeams, deck slab, bearings etc.

The load cases require some judgement, particularly where wind is concerned. Normally, the design of long span bridges includes wind-tunnel tests.

Seismic loading - you probably want site-specific data rather than using the generic curves.

AASHTO LRFD is applicable, usually supplemented by proeject specific design criteria. We typically incorporate some of PTI's recommendations for stay cable design, testing, and installation.

Also, ASCE has a slim booklet "Guidelines for the Design of Cable Stayed Bridges".

THe AASHTO Specs are applicable. The local (State DOT?) construction specs may also apply. There is also a Guide Spec for segmental concrete construction that may be helpful if it is made of concrete. Good Luck.