# Anchorage set losses

Anchorage set losses are caused by the movement of the tendon prior to seating of the wedges or the anchorage gripping device. A common value of these losses is about 10mm (AASHTO LRFD 2007).

If $\Delta_a$ is the anchorage slip and $L_a$ is the length along the tendon affected by the anchorage slip (Choudry 1986), then:

$\Delta_a = \int_0^{L_a} \Delta_{\epsilon} dx$

where $\Delta_{\epsilon}$ is the decrease in the tendon strain due to anchorage slip.

### Uniform distribution of anchorage losses

Assuming that the anchorage slip losses are uniformly distributed over the entire length of the tendon (in other words $\Delta_{\epsilon}$ is constant), then the following equations can be written:

$\Delta_a = \Delta_{\epsilon} L$

$\Delta_{\epsilon} = \frac{\Delta_a}{L}$

Noting that

$\Delta_{\sigma} = E_p \Delta_{\epsilon}$ and $\Delta F = A_p \Delta \sigma$

we can write the final equation for the loss of prestress force:

$\Delta F = A_p E_p \frac{\Delta_a}{L}$

where:

• $A_p$ ... area of the prestressing tendon
• $E_p$ ... Young's modulus of the prestressing tendon
• $\Delta F$ ... loss of prestressing force
• $L$ ... length of the tendon

## References

• AASHTO LRFD Bridge Design Specifications, SI Units, 4th Edition, 2007; Article 5.9.5.2.1, p. 5-109
• Deepak Choudry: Analysis of Curved Nonprismatic Reinforced and Prestressed Concrete Box Girder Bridges, Report No. UCB/SEMM-86/13, December 1986; p. 45 (Section 3.4.2: Anchorage Slip Losses)

 Home > Topics > Prestressed Concrete e Overview Overview  · Hyperstatic forces Prestress losses Friction losses  · Anchorage set losses Miscellaneous Tendon  · Post-Tensioning  · Partial prestressing  · Restraint moment  · Prestressing as action or resistance  · Standard prestressed girders  · Magnel diagram Related Topics Reinforced Concrete