Enumerate the term - superposing the stress variations

If the case of concentric pre-stressing is considered, we can appreciate that stress at any section of the beam is compressive in nature and its magnitude bver any cross-section is uniformly PIA. If no external load or self load of the beam is considered, the resultant force at any section shall be located at the centroidal axis. If other loads, such as external loads and self load of the beam, are also considered, stress pattern at any section is obtained by superposing the stress variations due to all loads. Knowing that the resultant force at any section is equal to the pre-stressing force, the location of this resultant force at any section can be determined so that the same stress pattern at the section is obtained.