Post-Tension Special Inspection

Before the pour

Tendon placement inspection covers profile, support and anchorage before concrete is placed. The drape controls the entire structural behavior of the slab, so height at support chairs is verified against the approved shop drawings across the tendon length, not sampled at one point.

• Tendon size, type, quantity and layout against approved shop drawings
• Tendon profile and drape height at supports and low points
• Support chair spacing and securement
• Live end and dead end anchorage installation, backing plates and pocket formers
• Sheathing condition, repairs to damaged sheathing, and encapsulation where required
• Clearance from openings, embeds and conventional reinforcement
• Verification that tendons are not displaced by traffic or subsequent trades before placement

Stressing and elongation

At stressing we witness the operation, record gauge pressures and measured elongations, and compare measured elongation to the calculated value on the approved shop drawings. Deviations outside the accepted tolerance are reported to the engineer of record before the tendons are cut, because after cutting there is no way to re-verify.

• Calibration certificates for jacks and gauges verified as current before stressing begins
• Gauge pressure and measured elongation recorded per tendon
• Comparison against calculated elongation and the specified tolerance
• Wire or strand slippage at anchorages noted
• Tendon cutting and pocket grouting witnessed after elongations are accepted

Common questions

What elongation tolerance do you work to?

The tolerance on the approved shop drawings governs. Where the drawings are silent, we confirm the acceptance criteria with the engineer of record before stressing rather than applying a default.

Can tendons be cut before elongations are reviewed?

They should not be. We report elongations that fall outside tolerance before cutting, because cutting removes the ability to re-stress or investigate.

Code basis and deliverables