Stress and strain of uncracked sections - Concrete Structures: Stresses and Deformations - page 42

32% of the initial compression in the concrete (1329 kN). The
higher percentage is caused by the compression picked up by the
non-prestressed steel as creep and shrinkage develop.
The results of this example may be checked by verifying that the sum
of the changes of the resultants of stress in concrete and steel is zero.
Thus the system of forces shown in Fig. 2.6(c) is in equilibrium.
A check on compatibility can be made by verifying that the change in
strain in prestress steel caused by (

∆ σ ps − ∆ σ pr ) is equal to the change in
strain in concrete at the prestressed steel level.
In Fig. 2.7, we assumed that the cross-section analysed in this

Figure 2.7 Axial strain, curvature and prestress loss in a post-tensioned span (beam
of Example 2.2).