SettingsSettings for this calculationUS
The length of the post-tensioned tendon.
This short-tendon method assumes the seating loss effect reaches the full tendon length — for very long tendons (over ~30m/100ft) a friction-affected-length method is more accurate.
The seating loss distance for your specific anchorage system.
Typically 1/4 in (6mm) to 3/8 in (10mm) — get the exact value from your anchorage manufacturer's data sheet.
The nominal cross-sectional area of one strand.
A standard 1/2 in (12.7mm) 7-wire strand has an area of about 98.7 mm² (0.153 in²) — check your strand's data sheet for other sizes.
Stress loss from anchor seating
12,100 psi
This simplified short-tendon method assumes the seating loss propagates the full tendon length — a licensed PT designer must verify this assumption and account for friction losses along the tendon for a final design.
- Stress loss (imperial)
- 12,117.35 psi
- Force loss per strand
- 1.85 kips
- Force loss per strand (imperial)
- 1,853.78 lbs
They open the calculator with your figures already in it
Post-Tensioned Anchor Seating Loss Calculator: 12,117 psi — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Post-Tensioning Institute (PTI) simplified short-tendon seating loss method: stress loss = (anchor set / tendon length) x strand modulus of elasticity — valid when the seating-loss effect propagates the full tendon length, the common case for short-to-medium span slab tendons
- Standard 7-wire strand elastic modulus: 28,500,000 psi; typical anchor set (wedge draw-in) is commonly 1/4 to 3/8 in depending on the anchorage system
Inputs used
- Tendon Length
- 49 ft
- Anchor Set (Wedge Draw-In)
- 0.25 in
- Strand Cross-Sectional Area
- 0.15 in²
Intermediate steps
- Stress loss (imperial)
- 12,117.35 psi
- Force loss per strand
- 1.85 kips
- Force loss per strand (imperial)
- 1,853.78 lbs
Confidence note: This simplified short-tendon method assumes the seating loss propagates the full tendon length — a licensed PT designer must verify this assumption and account for friction losses along the tendon for a final design.
What this calculation does not cover
- Friction is not in this model. It spreads the wedge draw-in uniformly over the entire tendon, ignoring the strand-to-duct or strand-to-sheathing friction that in a real tendon confines seating loss to a set-influence length near the stressing end. Where friction matters, the actual loss at the anchorage is higher than this figure and falls away to nothing further along the tendon.
- This is the seating loss alone, not the effective prestress. Elastic shortening of the concrete, creep, shrinkage, steel relaxation, and wobble and curvature friction along the tendon profile are all excluded, as is any set at the dead end.
- The strand modulus is fixed at the standard 7-wire value and cannot be changed. The result does not apply to threadbar or other bar systems, or to strand of a different grade or modulus. The force figure is per single strand and is not multiplied up for the strands in a tendon or the tendons in a slab.
- Nothing checks that the computed loss is physically achievable. The calculator never compares it against your jacking stress or the strand's breaking strength, so a very short tendon length returns a loss larger than the prestress the tendon could ever have held, with no warning on the page.
- This is not a post-tensioning design and does not replace one. Anchor set must come from the anchorage supplier's data for the system actually being installed, and the stressing sequence, tendon profile, jacking force and final effective prestress are a licensed PT designer's work.
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This result is a specification — 12,100 psi — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations2
- Post-Tensioning Institute (PTI) simplified short-tendon seating loss method: stress loss = (anchor set / tendon length) x strand modulus of elasticity — valid when the seating-loss effect propagates the full tendon length, the common case for short-to-medium span slab tendons
- Standard 7-wire strand elastic modulus: 28,500,000 psi; typical anchor set (wedge draw-in) is commonly 1/4 to 3/8 in depending on the anchorage system
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