Estimating Sheet

# Tips to work out the total loads on a column and related footing

Construction Software The process becomes complicated for engineering students while measuring loads for column and footings design. Here, in this article, the process is explained in a simple manner.

1. Self weight of the column x Number of floors
2. Self weight of beams per running meter
3. Load of walls per running meter

The columns are also dependent on bending moments which should have been included in the final design. It is suggested to employ advanced structural design software like ETABS or STAAD Pro for creating the design of a good structure.

The structural loading calculations are based on the following basic assumptions :-

For Columns: Self weight of Concrete should be approx 2400 kg per cubic meter, that is similar to 240 kN. Self weight of Steel should be approx 8000 kg per cubic meter.

Even if we guess a large column size of 230 mm x 600 mm having 1% steel and 3 meters standard height, the self weight of column should be approx 1000 kg per floor, that is similar to 10 kN. Therefore, for calculation purpose, the self weight of column is taken among 10 to 15 kN for each floor.

For Beams: The calculations are same as above. Here, it is supposed that each meter of beam contains dimensions of 230 mm x 450 mm exclusive of slab thickness. So, the self weight should be around 2.5 kN per running meter.

For Walls: The thickness of bricks fluctuate among 1500 to 2000 kg per cubic meter. For a 6″thick wall having 3 meter height and 1 meter length, the load per running meter is estimated as similar to 0.150 x 1 x 3 x 2000 = 900 kg that is equal to 9 kN/meter. This method can be used to work out load per running meter for any brick type.

For autoclaved, aerated concrete blocks like Aerocon or Siporex, the weight per cubic meter should be among 550 to 700 kg per cubic meter. If these blocks are used for construction, the wall loads per running meter become as low as 4 kN/meter, that leads to a major fall in the construction cost.

For Slab: Suppose the slab contains a density of 125 mm. Now each square meter of slab should contain a self weight of 0.125 x 1 x 2400 = 300 kg that is similar to 3 kN. Suppose, finishing load is 1 kN per meter and superimposed live load is 2 kN per meter. Therefore, slab load should be computed as approx 6 to 7 kN per square meter.

Factor of Safety: In the end, after computing the total load on a column, include it in the factor of safety. For IS 456:2000, the factor of safety should be 1.5. 