# Tendong grouting cause changes in stress in AQB, but it doesn't in CSM?

We know that for post-tensioned members, before tendon grouting, the net section is used; while after grouting, the transformed section is used.
So the section properties before and after grouting are different, therefore the stresses are different too.

But in CSM manual \$2.4,

All construction stages that cause changes of stresses have to be considered. Therefore
construction stage grouting / extrusion (CS: x2) is not necessarily to be computed, due to the
fact that the grouting mortar causes no changes in stresses.

Is it correct?

I guess it is noticed there that grouting itself does not case any loads, so if cs:x2 stage is not calulcated it is no problem, but after cs:x2 stage brutto section properties are used.

This is the official Sofistik Verification Example:
DCE-EN17: Stress Calculation at a Rectangular Pre-stressed Concrete CS
verification.dat\dcbenchmarks.dat\dce-en17\stress_prestress.dat

At mid-span of the beam:

1. Hand calculation & AQB:
prestressing moment on net section (before grouting)= -1435.91 kNm
prestressing moment on transformed section (after grouting) = -1406.11 kNm
on net section, moment = 1250-1435.91 = -185.88 kNm, the bottom stress = -4.82 MPa

on transformed section, moment = 1250-1406.11 = -156.08 kNm, the bottom stress = -4.51 MPa

2. CSM
on net section, moment = -185.88 kNm, the bottom stress = -4.82 MPa
Both are the same as those in AQB

on transformed section, moment = 1250-1406.11 = -156.08 kNm, the bottom stress = -4.82 MPa

The moment is the same as that in AQB’s transformed section. But the stress is the same as that in AQB’s net section.
Why???

dat is attached
stress_prestress - CSM.dat (2.9 KB)

replied to my self
The stress in transformed section in CSM is correct, because the stress before grouting is “locked in” the structure, it won’t change after grouting.