# Maximum Recommended Spacing for Unbonded Single-Strand Tendons in One-Way PT Slabs ## Introduction In post-tensioned (PT) slab systems, the spacing of tendons is critical for achieving uniform prestress and avoiding cracking. For **unbonded single-strand tendons** in **one-way slabs**, specific guidelines are provided by standards such as **ACI 318-11 Chapter 18** and **PTI detailing criteria**. ## Key Considerations - The code **does not explicitly limit** the spacing for one-way slabs. - Instead, the **spacing is determined based on slab thickness** and other practical considerations. - The **larger of** the following two values** is generally recommended for tendon spacing: 1. **5 ft (feet)** 2. **8 times the slab thickness** ## Explanation - The **spacing** should ensure proper force distribution and minimize cracking. - When the slab thickness is small, the **8 times the slab thickness** criterion controls. - When the slab is thicker, **5 ft** may be the limiting factor. ## Final Recommendation According to **PTI detailing criteria** and the typical interpretation of standards: > The **maximum spacing** for unbonded single-strand tendons in one-way slabs is **the larger of 5 ft and 8 times the slab thickness**. ### Therefore: \[ \boxed{ \text{Maximum spacing} = \max \left( 5\, \text{ft},\ 8 \times \text{slab thickness} \right) } \] ## Summary - **No explicit code limit** specifically for one-way slabs. - Use **the larger value** between **5 ft** and **8 times the slab thickness** for tendon spacing. **Final answer:** **The larger of 5 ft and 8 times the slab thickness.**