Hi, I am in huge confusion while designing an any RCC structure in staad pro. Problem started when you increase the section size to make it pass and Run again the analyser.

Thus the increased size of the member changes in the Dead Load (self-weight)  and corresponding Joint weight (for Dynamic Analysis by Joint Load Method). hence further increase in the Bending Moment, Shear Force, Torsion etc. this further tends to increase in the size of member. ( Like Z Beam at staircase which cannot be designed in RCDC due to level difference.)

Similar things happens when you design a member in RCDC and increase the Size to make it pass. lets say a beam of 300 x 500 mm in the staad model with B.M. 'X' and Shear 'Y' passes in RCDC by the increased size of 400 x 600 mm for the same BM 'X' and Shear 'Y'.

But when you update the analysis file the beam fails again for increased B.M. 'X1' and Shear'X1'. As you know heavy section attracts heavy shear. 

This analysis and design became worse with ductile design. member fails in sway shear fails again and again with changes in size. 

So I would obliged if anyone enlighten this problem and show how to end this cycle and conclude on a optimized section.