The spacing between reinforcing bars may not exceed which value?

• A. Three times the panel thickness
• B. Eighteen inches
• C. The lesser of three times the panel thickness or eighteen inches
• D. The greater of three times the panel thickness or eighteen inches

Answer: (C)

In tilt-up panels, reinforcing bar spacing is limited to ensure crack control and effective load transfer across the panel. The maximum spacing is the lesser of three times the panel thickness or eighteen inches. This means the bar spacing tightens as the panel gets thinner (since 3t becomes smaller) and never exceeds 18 inches for thicker panels (since 18 inches caps the spacing). For example, a 6-inch-thick panel allows up to 18 inches (since 3t equals 18), a 8-inch-thick panel is limited to 18 inches (3t is 24), and a 3-inch-thick panel is limited to 9 inches (3t is 9). This approach keeps reinforcement density appropriate across different panel sizes.