Common types of cracks in reinforced concrete column

Usually, Four types of cracks are found in reinforced concrete column which range from diagonal cracks, horizontal cracks, splitting cracks, corrosion cracks. The cracks happen in columns due to improper design, defective construction or overloading, erosion of reinforcement, isolated settlement of foundations, creep and shrinkage.

Cracking in reinforced concrete column may result in loosing of strength, consistency, longevity, and adversely impact aesthetics.

Types of cracks found in concrete columns:

1. Diagonal Cracks: If there are diagonal cracks in reinforced concrete columns, they encircle the whole face of column anywhere along its height. Because of insufficient load bearing strength of the columns, inadequate cross-section and inadequate reinforcement steel.

Diagonal Cracks significantly impact the structural soundness and therefore it should be monitored carefully.

2. Horizontal Cracks: Horizontal crack in reinforced concrete column is generally found at the beam-column joint, and on column face where tensile stress is massive. Columns with insufficient moment resistance strength, inadequate reinforcements, or disposition of installed reinforcement may lead to horizontal cracking owning to the effect of shear force and direct load and uniaxial bending.

Finally, horizontal cracks significantly decrease the shear strength of the column and as a result there is high risk of failure. So, it should be dealt with instantly and carefully.

3. Splitting Cracks: Splitting cracks in reinforced concrete column belong to short parallel vertical cracks having non-uniform width. These types of cracks may occur in columns with insufficient steel reinforcement, and low concrete quality. Splitting cracks in concrete columns originated because of attaining its maximum load bearing strength.

The ultimate Load bearing strength of the column is exceeded when concrete cross section is not enough or reinforcement ratio is inadequate or combination thereof.

4. Corrosion Cracks: Corrosion cracks in concrete columns are formed along the line of reinforcements. These types of cracks are usually homogeneous in width and expand as the column is ageing.

Probable reinforcement erosion and insufficient bond among the concrete and steel bars lead to erosion reinforcement in concrete columns. If these types of cracks are not dealt with properly, the erosion of reinforcement will be increased at a rapid rate.



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Published By
Rajib Dey
www.constructioncost.co
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Bar Bending Schedule For Floor Slabs

Bar bending schedule is an important structural working document that rightly gives the disposition, bending shape, total length, and quantity of all the reinforcements that have been provided in a structural drawing.

It is often provided in a separate sheet (usually A4 paper) from the structural drawing.

The bar marks from structural detailing drawing are directly transferred to the bar bending schedule. We normally quantify reinforcements based on their total mass in tonnes or kilograms. For smaller projects, you can quantify based on the length needed.

Unit mass of rebars

The unit mass of the reinforcements is obtained from the density of steel. The density of steel provided for this purpose is 7850 kg/m3.

Suppose, there is a bar with 12mm dia;

The area is calculated by (πd2)/4 = (π × 122)/4 = 113.097mm2 = 0.0001131m2

Based on a unit length of the bar, it is established that the volume of a metre length of the bar is 0.0001131m3.

Density = Mass/Volume = 7850 kg/m3 = Mass/0.0001131

So, the unit mass of 12mm bar = 7850 × 0.0001131 = 0.888 kg/m

So, for any diameter of bar;

Basic weight = 0.00785 kg/mm2 per metre

Weight per metre = 0.006165 ϕ2 kg

Weight per mm2 at spacing s(mm) = 6.165ϕ2/s kg

Here;
ϕ denotes diameter of bar in millimetres
Bending Shapes
There exist some basic standard shapes with specific shape codes in the code of practice.
The length of reinforcement bars can be determined with the following relation;

Length of bar = Effective Length + Width of Support – Concrete cover (s) – Tolerances
The standard values of tolerances (deductions) are provided in the table below;

To get more details, go through the following link structville.com

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Published By
Rajib Dey
www.constructioncost.co
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