## Ecentricity limits and tendon profile

**Eccentricity Limits and Tendon Profile**

Since the moments change along the length of a beam, we must change some aspect of the prestress also. The only remaining variable is the eccentricity.

**Tension on Top at Transfer**

We determine an expression for the eccentricity in terms of the other knowns:

Hence we have a lower limit for the eccentricity as:

**Tension on the Bottom in Service**

Using

Hence we have an upper limit for the eccentricity as:

Since the upper and lower kerns (the Z_{t}/A and Z_{b}/A quantities) are constant for constant geometry, and since P is also constant, it can be seen that the cable limits follow the same profile as the bending moment diagrams at transfer and in service.