The maximum spacing between reinforcing bars is determined by which factors?

• A. Panel thickness and the 18 inch limit
• B. Panel length and panel width
• C. Bar diameter alone
• D. Concrete strength

Answer: (A)

In tilt-up panels, how far apart reinforcing bars can be spaced is limited by the panel’s cross-section and a practical cap of 18 inches. The panel thickness sets how much concrete surrounds each bar, which is essential for proper cover, bond, and crack control, while the 18-inch limit provides a universal upper bound to ensure there’s enough concrete to transfer stresses and maintain structural performance across the panel.

Panel length, panel width, bar diameter, or concrete strength don’t determine this maximum spacing. The diameter affects minimum spacing (to avoid crowding) and the strength influences capacity, but the spacing cap itself comes from the panel thickness combined with the 18-inch rule.