# Maximum Recommended Spacing for Unbonded Single-Strand Tendons in One-Way PT Slab ## Background In post-tensioned (PT) concrete slabs, the spacing of tendons is important for ensuring proper load transfer, controlling crack widths, and maintaining structural integrity. For unbonded single-strand tendons in one-way slabs, specific guidelines are provided by standards such as ACI 318-11 and PTI detailing criteria. ## Key Point - **The spacing is not explicitly limited for one-way slabs** in the standards. - However, recommendations are often based on practical considerations related to slab thickness and tendon effectiveness. ## Relevant Criteria ### ACI 318-11 Chapter 18 and PTI Detailing Criteria - **The general guideline** for tendon spacing in one-way slabs, especially when explicit limits are not provided, is to use a **recommended maximum spacing based on slab thickness**. ### Common Recommended Spacing - The **larger of**: - **5 ft (60 inches)**, or - **8 times the slab thickness** (t) - Alternatively, other criteria sometimes cited include: - **4 times slab thickness** - **6 ft (72 inches)** ## Final Determination Based on the typical recommendations and the provided options, the most commonly accepted maximum spacing for unbonded single-strand tendons is: ### **The larger of 5 ft and 8 times the slab thickness** This ensures tendons are spaced sufficiently close to control crack widths and provide effective prestressing. ## **Final Answer:** ### **The larger of 5 ft and 8 times the slab thickness**