Posts Tagged Design of columns
Guidelines to be followed for making a column layout
In this article, we will go through the essential thumb rules to be followed for giving a column layout. Ofcourse columns have to be designed in accordance to the total forces acting on the structure, but apart from that, it is essential for every Civil engineer and Architect to remember a few thumb rules so that they are prevented from making mistakes.
Three thumb rules to be followed are as follows:
- Size of the Columns
- Distance between Columns
- Alignment of columns
Minimum Size of RCC columns
The size of the columns depends on the total load on the columns. There are axial loads and lateral loads. Large beam spans induce bending moment not only in the beams, but also in columns which are pulled by the stresses in the beams. It is important to use advanced structural design software like ETabs or Staad pro. I highly recommend every structural designer learn these software. The thumb rules are for general designing in very small projects.
For this general thumb rule, we will assume a structure of G+1 floors high, using standard 6″ walls.
Minimum size of an RCC column should not be less than 9”x 9” (225mm x 225mm) with 4 bars of 12 MM Fe500 Steel.
These days the minimum I use in my projects is 9″ x 12″ (225 mm x 300mm) with 6 bars of 12 MM Fe500 steel. You can never go wrong with strong columns. I also recommend use of M20 grade concrete for the structure (ratio 1 part Cement : 1.5 parts Sand : 3 parts Aggregate with 0.5 parts water by volume). I recommend use of 8 MM stirrups at a distance of 150 MM center to center throughout the length of column.
This setup of 9″ x 12″ RCC columns is safe for G+1 Floors. There are a lot of other considerations, but this is just a thumb rule.
Reinforced Concrete Columns
A column is a very important component in a structure. It is like the legs on which a structure stands. It is designed to resist axial and lateral forces and transfer them safely to the footings in the ground.
You can manually calculate the superimposed loads on a column in a structure using a simple process outlined in this linked article. You might also like this RCC Column design app which can then be used to calculate longitudinal steel reinforcement in a column for a given axial load.
Columns support floors in a structure. Slabs and beams transfer the stresses to the columns. So, it is important to design strong columns.
A column is defined as a compression member, the effective length of which exceeds three times the least lateral dimension. Compression members whose lengths do not exceed three times the least lateral dimension, may be made of plain concrete.
The axial load carrying capacity of a column is deduced from the formula
Please see the link for formulas to calculate axial loads in columns. I would recommend using advanced structural design software like ETabs or Staad Pro for design of structures. Column design does not depend only on axial loads, but also on many other factors. There are bending moments and tortional forces induced due to beam spans, wind loads, seismic loads, point loads and many other factors.
In this article, we are going to discuss in detail the basis of classification of columns and different types of reinforcement required for a certain type of column.