Concrete Design > RC Materials prompts you with the following dialog.
It allows you to define concrete and reinforcement strength properties for the existing materials. The strength properties include:
•Concrete compressive strength fc
•Concrete reinforcement strength fy
•Concrete stirrup or tie strength fys
If standard materials are used in Create > Materials, these strength properties will be set automatically. You may override these properties prior to performing concrete design. No concrete design will be performed on a member or shell if its f'c is zero. You should not modify materials that are not concrete on this dialog.