How to calculate the load in a column
whenever we start the construction process of a building, the first step we need to do is the excavation of the foundation and to start the excavation process, we need to know the size of the footing, which cannot be determined without knowing the load carried by the column above the footing since we. Design all the elements before starting the construction process. But in case we need to know the approximate size of the footing, then we must calculate the loads on the columns and with the help of which it’s easy to know the size of the footing. Let’s consider a 2 story building with 12 columns number from C 1to C 12 and 19 beams from B1 to B19 out of which B13 and B15 or second beams. Let’s calculate the approximate actual load on column 6 which is connected by the beams B5B9B12 and B8.
Number of Stories = 2, Floor Height = 3m
Size of Primary Beam = 230 mm x 300 mm
Size of Secondary Beam = 230 mm x 230 mm
Size of the Column = 230 mm x 300 mm
Wall thickness (External) = 230mm
Wall thickness (Internal) = 230mm
Soil Bearing Capacity = 150 kN/m²
Height of Neck Column (Footing top to G.L) = 1m
Hight of Plinth beam above G.L = 600mm
Thickness of Roof/Floor Slab = 125 mm
Width of ABCD
= 1/2 * (4 + 4) = 4m
Length of ABCD
= 1/2 * (4 + 6) = 5m
Area of ABCD
= 5 * 4 = 20sqm
We assume
Live load on Roof Slab = 1.5 kN/m²
Live load on Floor Slab = 3 kN/m²
Floor finishing = 1 kN/m²
Waterproofing load = 0.8 kN/m²
Load on Roof Slab:
Thickness of slab = 125mm
Self-weight = Thickness of slab x Density of RCC = 0.125m x 25 kN/m³ = 3.125 kN/m²
Live load = 1.5 kN/m²
Floor finish = 1 kN/m²
Waterproofing = 0.8 kN/m²
Total load on Roof = 3.125 +1.5 +1 +0.8=6.425 kN/m²
Total Factored load on Roof = 1.5 x 6.425 = 9.64 kN/m²
Load on Floor Slab:
Thickness of slab = 125mm
Self-weight = Thickness of slab x Density of RCC
= 0.125m x 25 kN/m³ = 3.125 kN/m²
Live load = 3 kN/m²
Floor finish = 1 kN/m²
Total load on Floor = 3.125 + 3 + 1 = 7.125 kN/m²
Total Factored load on Floor = 1.5 x 7.125 = 10.69 kN/m²
Load on Beams:
Self-weight of Primary Beam = 0.23m x 0.3m x 25kN/m3 = 1.725kN/m
Factored Self weight of Primary Beam = 1.5 x 1.725 = 2.587 kN/m
Self-weight of Secondary Beam = 0.23m x 0.23m x 25 kN/m3 = 1.322 kN/m
Factored Self-weight of Secondary Beam = 1.5 x 1.322 = 1.983 kN/m
Wall Loads:
Height of External/Internal Walls = Floor Height – Depth of Beam = 3m-0.3m = 2.7 m
Self-weight of External wall = Thickness of wall x Height of wall x Density of Brick masonry = 0.23m x 2.7m x 20kN/m³ = 12.42 kN/m
Factored self-weight of External wall = 1.5 x 12.42 = 18.63 kN/m
Self-weight of Internal wall = 0.23m x 2.7m x 20kN/m³ = 12.42 kN/m
Factored self-weight of Internal wall = 1.5 x 12.42 = 18.63 kN/m
Load transferred to C_{6} from each floor:
Area of Slab surrounding the C6 = Area of ABCD = 20 m²
Length of primary Beams surrounding C6= 1/2 ( Length of B8 + Length of B_{9} + Length of Bs + Length of B 12 )= 1/2 (4+4 + 4 + 6 )=9m
Length of Secondary Beams Surrounding C6 = 1½ x Length of B_{13} = 1/2 * 6 = 3m
Wall Length under primary Beams = 9m
Wall length under secondary Beams = 0 m
Load transferred from Roof to 1st floor:
Roof load (in terms of kN) = Total factored load on Roof x Area of Roof surrounding C6 = 9.64 kN/m² x 20m² – 192.8 kN
Beam Load (Primary) = Factored Self weight of Primary Beams x Length of Primary Beams = 2.587 kN/m x 9m = 23.28 kN
Beam Load (secondary) = Factored Self weight of secondary Beams x Length of secondary Beams x 1/2 = 1.983 kN/m x 3m x 1/2= 2.98 kN
Wall Load (Primary) = Factored Self weight of Primary walls x Length of Primary walls = 18.63 kN/m x 9m = 167.7 kN
Wall Load (secondary) = 0
Total Load From Roof to 1st Floor= 192.8 +23.28 +2.98 +167.7 = 387 KN
Load transferred from 1st Floor to Plinth: Floor load (in terms of kN) = Total factored load on Floor x Area of Floor surrounding C6 = 10.69 kN/m²x 20m² 213.8 kN
Beam Load (Primary) = Factored Self weight of Primary Beams x Length of Primary Beams = 2.587 kN/m x 9m = 23.28 kN 4
Beam Load (secondary) = Factored Self weight of secondary Beams x Length of secondary Beams x 1/2 = 1.983 kN/m x 3m x 1/2 = 2.98 kN
Wall Load (Primary) = Factored Self weight of Primary walls x Length of Primary walls = 18.63 kN/m x 9m = 167.7 kN
Wall Load (secondary) = 0
Total Load From 1st Floor to Plinth = 213.8+23.28 +2.98 +167.7 = 408 KN
Load transferred between Plinth Beam & footing (No walls and no Secondary Beam):
Beam Load (Primary) = Factored Self weight of Primary Beams x Length of Primary Beams = 2.587 kN/m x 9m = 23.28 kN
Total = 23.28 kN
Total Self-weight of Column = Column Cross-sectional Area x Height of Column x Density of RCC
Column Cross-section = 230mm x 300mm
Height of Column = 2(Floor Height) Depth of Plinth Beam Depth of Neck Column = 2(3m) + (0.6m) + 1m = 7.6m
[Note:- Neck column is the portion of the column from footing top up to the ground level]
Total Self-weight of column = 0.23m x 0.3m x 7.6m x 25kN/m³ = 13.11 kN
Total Load on C6 = 387 KN + 408 kN + 23.28 +13.11 = 832 kN
For interior columns, we should consider an increment of 0 to 10%, For side columns -11% to 15% and for corner columns-16% to 33%.
After adding 10% of extra load,
Total axial Load on C6 = 832 kN x 1.1 = 915kN