Post-tension design optimisation

Most slab designs carry material that does not need to be there. Thickness is chosen early and never revisited, the load balancing target is set conservatively for every bay, mild steel is added on top of prestress where the analysis did not need it, and punching is solved with thickness instead of shear reinforcement. Optimisation revisits these choices with the full model.

Typical levers

• Slab thickness: checked against deflection, vibration, punching and fire cover rather than span-to-depth rules alone.
• Prestress level: balanced load and precompression tuned per strip, so heavily loaded bays get what they need and others do not.
• Tendon layout: banded and distributed tendons arranged to cut strand length, anchor count and clashes with services.
• Bonded reinforcement: top and bottom steel reduced to what the code and the analysis require.
• Punching shear: shear studs or drop panels where they are cheaper than a thicker slab.
• RC to PT conversion: where an RC scheme is used for long spans, a PT alternative is studied with a like-for-like comparison.

Quantities in the comparison come from the two models, so the team can price them with its own rates. We do not publish percentage savings because they depend entirely on the starting design; the study shows the actual numbers for your project.

Optimisation works best before tender or early in construction, when the PT contractor has not yet ordered materials. Late-stage optimisation is still possible floor by floor, but changes must be coordinated with drawings already issued. For a check without redesign, see PT design review. To compare systems at concept stage, see preliminary design support, and our guide on PT vs RC slabs.

The optimised design stays contractor-neutral: it uses the friction and anchorage data of the approved PT system, so any specialist contractor can build it. Iron Axis has no stake in PT materials or site works, which keeps the recommendations focused on the structure rather than on product quantities.