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 F. 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 3 in. 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.