Stress and strain of cracked sections - Concrete Structures: Stresses and Deformations - page 262

Figure 7.14 Analysis of strain and stress distributions in a partially prestressed
cracked section (Example 7.6).
The total stress in concrete after the live load application is simply
equal to the stress due to N 2 and M 2 (Fig. 7.14(b) ).
7.9 General
The methods of analysis presented in this chapter give the axial strain and
curvature in a fully cracked section, referred to as state 2. In this state the
concrete in tension is fully ignored. It is well established that concrete,
although weak in tension, participates in the rigidity of cracked members as
will be discussed in Chapter 8. The axial strain and curvature calculated for a
fully cracked section do not represent actual values from which displacements
can be calculated. They only represent upper bounds of strain and curvature.