i applied prestressing force eventhough my moment value is same as without apply the pretension kindly clarify me(staad CE)

Question

Marcelo F. DaSilva · Answer

hi prashanth p 
 Your results seems just fine.. 
 Taking a deeper look at the axial load (Fx) at node 16 which is part of element 398. Here is the break down: 
 Dead = -1859 kN 
 Live = -1572 kN 
 Wind = -209 kN 
 load comb 4 = LC4 = (D + L + W) = -(1859 + 1572 + 209) = -3640 kN (staad -3640.2 kN highlighted in RED) 
 prestress = -1500 kN 
 load comb 6 = (LC4 + 5) = -3640 + -1500 = -5140 kN (staad -5140.2 kN highlighted in BLUE) 
 
 Regarding the moment, in theory you should expect ZERO moment due to prestressing force because you are applying the presstressing force at the center of the element (no eccentricity). HOWEVER, because you are analyzing a hyperstatic structures and also the members are slightly inclined (due to cone-like shape of the tower). This induces some secondary moments and shear as you can see some small values shown in the results table. 
 Prestress at node 16 --> Fy = -0.222 kN and Mz = -0.93 kN-m (see light blue)