This page provides information on how the program calculates prestress losses.

On this page:

Overview of Prestress Losses

The prestress losses accounted for in SAP2000 can be classified as follows:

• short term losses (immediate losses that occur before and during transfer):
  • anchorage set (anchorage slip losses)
  • elastic shortening
  • friction losses, due to length (or wobble) effect and curvature effect
• long term losses
  • due to concrete creep
  • due to steel relaxation
  • due to shrinkage

Short Term Losses

Anchorage Set Losses

Losses due to anchorage set are NOT uniformly distributed along the entire length of the tendon. Rather, the length of the tendon affected by anchorage set is calculated as a function of the friction losses:

where,

• Unknown macro: {math}

  Delta_

  Unknown macro: {set}
  = Anchorage set

• Unknown macro: {math}

  A_

  Unknown macro: {PS}
  = Cross sectional area of the tendon

• Unknown macro: {math}

  E_P

  = Young’s modulus of the tendon

• Unknown macro: {math}

  P

  = frictional loss expressed as a change in force per unit length calculated from a tendon force variation diagram

Elastic Shortening Losses

Friction Losses

Long Term Losses

Concrete Creep Losses

Concrete Shrinkage Losses

Steel Relaxation Losses

References

• Deepak Choudry: Analysis of Curved Nonprismatic Reinforced and Prestressed Concrete Box Girder Bridges, Report No. UCB/SEMM-86/13, December 1986 (contains equations for tendon losses)