scope:

This standard shall apply to precast concrete diaphragms and collectors that are part of the seismic-forceresisting system in structures assigned to SDC C, D, E, or It is permissible to use this standard for the design of the same elements in structures assigned to SDC B. 

This standard shall apply to precast concrete diaphragms, including a) through c):

a) Diaphragms that consist of a cast-in-place composite topping slab with a thickness of less than 75 mm on precast concrete members

b) Diaphragms that comprise precast concrete members with end strips formed by either a cast-in-place composite topping or edge beams

c) Diaphragms of interconnected precast concrete members without cast-in-place concrete topping.