What Is Column?
RCC column is a vertical structural member which transfers loads from beam and slab directly to the underneath soil. That means an entire building stands on columns. Most building failure occurs not only for design fault but also for poor construction practices.
Therefore it is essential to know the construction procedure of RCC column appropriately. Let us learn the basic construction process of RCC column.
RCC Column Construction Process
RCC columns are mainly constructed in four different stages, which are
- Column Layout Work.
- Column Reinforcement Work.
- Column Formwork and
- Pouring Concrete,
1. Column Layout Work
This is the first step of column construction. In this step, the location of columns is decided practically in the field. It is done by laying rope as per the grids shown in the drawing and afterward, the location of columns is marked.
2. Column Reinforcement Work
When marking of column location is done, the reinforcement of columns is placed according to the structural drawing.
For example, C1-12#16 mmØ and stirrup-10 mmØ@4″c/c.
This means the column C1 will have 12 numbers of 16 mm diameter bars as the vertical bar and 10 mm diameter steel should be placed 4 inch center to center spacing as the stirrup.
Lets look for another example, C2-8#20 mmØ +10#16 mmØ and stirrup – 10 mmØ @(4″+6″)c/c
So the column will have 8 numbers of 20 mm dia bar and 10 numbers of 16 mm dia bar for vertical reinforcement and (4″+6″) c/c means the middle half portion of clear height of column will have 6″ center to center spacing of stirrups and the upper one-fourth as well as bottom one-fourth height of the columns clear height will hold stirrups at 4″ center to center spacing.
Additional notes such as lap length for column steel of different diameter etc, will be given in the sheet of structural drawing.
3. Column Formwork
The floor height is normally kept at 10 feet. If the slab contains beam, then concrete has to be poured upto the beam bottom level. For example, if the beam height given in the drawing is 1′-6″, the casting height of column and formwork will be 8′-6″.
But as we know dropping concrete more than 5 feet height is not allowed because it will cause segregation, so we should create formwork within 5 feet height. When the first part is cast completely, the rest part should be started.
4. Pouring Concrete Into Column
Concrete pouring is the final step for column construction. It can be done in two different methods.
- Manually
- Using machine or pump.
Points To Be Followed During And After Concreting
1. Use machine mix concrete for less amount of concrete, and ready-mix concrete for larger amount of concrete.
2. Approval of placing concrete whether manually or by pump should be taken from the client.
3. Concrete should be poured upto slab bottom and the remaining column should be concreted during beam and slab concreting.
4. Mechanical vibrator must be used for full compaction of the column, but remember excess vibration can create segregation of the concrete. So each layer should be compacted properly.
5. The target slump is 160 mm.
6. Concrete should not be poured from more than 1.5 m height.
7. Always avoid construction joints in the column.
8. Covers should be given properly as per the structural drawing.
9. During concreting pouring, the temperature should be below 30º.
10. Check the verticality and horizontality of the column after pouring and vibrating the concrete.
FAQ
How are concrete columns constructed?
In summary, to cast a concrete column, it is necessary to prepare the formwork, place the reinforcement, pour and compact the concrete, remove the formwork, and finally, properly cure the column to ensure its strength and durability
What is the sequence of column construction?
Column construction sequence: (a) footing reinforcement; (b) prefabricated UHPC shell; (c) UHPC step between the footing and the column; (d) casting of column concrete; (e) connecting specimen to actuator; and (f) complete test setup
What is the RCC column construction process?
The construction process of RCC columns can be divided into the following four phases: 1. Column layouts – The first step in column construction is determining the layout of the columns. This involves placing ropes in the grid lines and labeling the position of columns
What is the maximum distance between two RCC columns?
There is no limit for distance between columns. Generally the distance between two RCC columns is taken to be 5 m considering safety as a prime criteria. But we can increase the span length up to 7.5 m
What is the design procedure of column?
The design of column refers to the process of determining the size, shape, and material requirements for a structural column that can support the load it will bear, while maintaining stability and safety. The design of columns is determined by the slenderness ratio of the columns and the load types on the columns
What is the minimum size of RCC column?
In the case of columns of the minimum dimension of 200 mm or under, whose reinforcing bars do not exceed 12 mm, a nominal cover of 25 mm may be used. The cross-sectional area of longitudinal reinforcement shall be not less than 0.8 percent nor more than 6 percent of the gross cross sectional area of the column
