The prestress response is calculated based on the tendon force after losses. The loss of prestress in the analysis is based on short-term and long-term losses. The short-term losses are calculated at Initial case, considering the anchor set and friction losses explained earlier. The Initial stage does not include any elastic shortening losses. The long-term losses depend on the loss type selected for the analysis. These can be lump sum, or time dependent methods.

The lump sum loss is based on a specified fixed amount of stress; however, since CIP RC/PT Girder uses transformed section properties, the effective loss of prestress is slightly less than the specified amount.

The time-dependent method includes the calculation of creep, shrinkage, and relaxation strains based on the material properties and equations specified in LFD 9.16.1, Eq. 9-1 and LRFD 5.9.5.2.2b, Eq 5.9.5.2.2b-1. The effect of these strains on the tendon stress is calculated automatically by using transformed sections. CIP RC/PT Girder uses a time of 10,000 days for calculating the ultimate creep and shrinkage effects; therefore, the effective strains may be slightly less than what is specified as ultimate values.

• Loss by Code Equation

AASHTO Standard and LRFD Specifications present simplified estimates of losses as well as equations for what is called the detailed method of loss calculations. CIP RC/PT Girder does not use the simplified estimates. However, the equations are used to calculate losses for each tendon for various effects, including, elastic shortening, shrinkage, creep, and relaxation. According to the code, these losses depend on stress responses at location of maximum moment. The location of maximum moment is based on the location of maximum positive response due to self weight for the range of the bridge that falls within the tendon length.

The equations for Loss by Code Equation are shown in the following table.

In these equations, when material properties are needed (e.g., RH), they will be based on the location of maximum moment. The modulus of elasticity of concrete (Eci) and steel (Ep) are calculated based on the initial strength of concrete (f'ci) and that of the tendon.

The stresses (fcgp and fcdp) are calculated based on loads at the Initial and Final cases. CIP RC/PT Girder calculates these stresses, and thus losses, only if the self weight is included in the analysis. The stress, fcgp, is the stress at the location of the tendon for all dead loads and the prestress included in the Initial case. The stress, *fcdp, is the difference between the stresses from all dead loads at the final case and the stresses for all dead loads at the in initial case. Note that all defined loads are included in these calculations regardless of whether are included in a combination or not.

The value of FR in the CRS equation is equal to the 0.7*fpu minus the initial stress value in tendon after losses due to anchor set and friction. If this value is negative, it is taken as zero. Note that these losses are only reported as feedback, and are not actually used in any stress calculations.