Leaderboard

I can discern this is due to the moment as your base is fixed and probably the governing combination include lateral loads. Few checks that you need to perform: 1. Are columns sway special in ETABS? If yes then why? 2. Can you tie these columns with tie beams at PARKING or BASE level to reduce critical length of column? 3. If PARKING to BASE height is 1m then from scale of the attached image, PARKING to 1ST FLOOR is just 2.5m. Is it right? Base on the grid spacing of 2.5m, I do not see any problem having 300x300 columns with 2 to 3% reo giving 1800 to 2800 square mm. Or you are not concerned about sizing and just curious why the increase in reo? If so, check the bending moment on governing load combination and you will get a fair idea what's happening here.