For the fixed catwalks, as for the floors themselves, if not subject to other things, one may use whatever seems suitable for the use from ordinary building codes.
Then there is some mechanical machinery that needs be fixed to the structure. The machinery itself will be conceived by someone that will be able to give definition of the loads it will be imparting to the building through the attachments. Contact the theater machinery provider, and talk to him about what impact factors are ordinarily used for quick movements of counterweights and screens and so on, and of course ask him the pertinent data for his design.