As a thumb rule we can calculate the size of column for G+1F for residential building. First assume load per floor for residential building as 1.5 t/m^2. For max distance of column is 5m span. Total load on column = No. floors x tributary areax load intensity per floor. = 2x (5x5m)x1.5 t/m^2=75 t . Multiply by 10 to get kn= 750 kn. Breadth b assumed=23cm. Depth required= 750/23=32.61cm say 30cm or 38cm. Column size is 23x 30cm or 23 x38cm. If you provide less size steel will be more. If you assume higher size steel required will be less. Provide 6 nos 12mm with 8mm dis ties at 150 mm c/c
First decide load coming on column. Total load =No. of storeys x Tributary area xLoad per m^2 per floor. For residential building we assume 15 to 20 KN/m^2. For Pu=970 KN say (calculate load as per plan) Pu=0.40fck Ac+0.67 fyAsc For M20 and fy415 steel assuming 2.50% steel Pu=0.40 x20 (0.975 Ag) +0.67x415 x0.025Ag Pu=7.80Ag+6.951 Ag =14.75 Ag. In this Pu=16875 x10^3 =14.75 Ag Ag=970x10^3/14.75=65762.71 mm^2 Assuming square section side of column=256.44mm say 300mm . Provide 300 x 300 mm square column.. We can Tabulate the various percentage of steel for M20 concrete and fy 415 steel pt=0.80% Pu=8.16 1.0% Pu=10.70 1.50% Pu=12.05 2.0% Pu=13.40 2.50% Pu=14.75 3.0% Pu=16.10 For economical max percentage of steel may be 2.50% may be adopted. This is for simplication.
Hi, If the column is at corner side then should I use 4 16mm bar for 10" x 10"? And for the middle of the slab like near the stair... 6 16mm rod for 10" x 12"? Is it ok to go?
