PT slab design checklist (ACI 318-19 and PTI)

This checklist reflects common practice for two-way PT slabs designed to ACI 318-19 with guidance from the Post-Tensioning Institute (PTI), including the PTI DC80 series of design guides. It is a general aid, not a substitute for the code, the project specification or engineering judgement.

1. Design basis

• Governing code edition, loading standard and the project specification identified.
• Concrete strength at 28 days and at transfer; strand grade, area and modulus; PT system and its friction (μ) and wobble (K) coefficients.
• Exposure class, cover, fire rating and required minimum thickness.
• Bonded or unbonded system stated, and the slab classified (for example class U for two-way slabs).

2. Loads and load balancing

• Self-weight, superimposed dead, live load and partitions, with any reductions justified.
• Balanced load as a sensible fraction of self-weight, typically checked against PTI guidance for the slab type.
• Average precompression within the usual range for two-way slabs (ACI 318 sets a minimum of 0.9 MPa / 125 psi effective precompression).

3. Prestress losses

• Friction and wobble, anchor seating, elastic shortening, creep, shrinkage and relaxation, either calculated or by a justified lump-sum.
• Effective force per tendon reported at the critical sections.

4. Stresses

• At transfer: compression and tension limits for the concrete strength at stressing.
• At service: flexural tensile stress within the limit for the slab class, with bonded reinforcement where tension exceeds the threshold.

5. Strength

• Flexural strength with factored loads plus secondary (hyperstatic) effects.
• Stress in tendons at nominal strength using the correct expression for bonded or unbonded tendons.
• Minimum bonded reinforcement at columns and in positive moment regions as required.

6. Punching and one-way shear

• Two-way shear at every column, including edge and corner columns, with unbalanced moment transfer.
• Openings near columns deducted from the critical perimeter.
• Shear reinforcement (studs or stirrups) where required, and drift compatibility checks for slab-column connections in higher seismic design categories.

7. Serviceability

• Immediate and long-term deflection, including creep and cracking, against the project limits.
• Vibration where relevant for long spans or sensitive occupancies.
• Restraint to shortening from walls and cores; pour strips and sequence.

8. Detailing and drawings

• Tendon layout, profile and chair heights, minimum radius and spacing, and clearances to openings.
• Anchorage zones with bursting and spalling reinforcement.
• Stressing sequence, transfer strength and calculated elongations for every tendon.
• A note that the slab is post-tensioned, and that coring needs scanning and approval.

9. Submission

• Calculation report clause-referenced to the code, with model files provided.
• Authority review checklist completed where one applies; see full post-tension design package.

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