Guideline for determining width, depth & reinforcement of beam

The minimum percentage of tension steel reinforcement utilized in the section of the beam should be close to around 0.3 per cent. The depth of the b..

What is the guidance for determining the width, depth, and reinforcement of a beam?

The following Top 8 guidelines for beam may be used for choosing the dimensions of R.C. beams Section

Guideline 1

The minimum percentage of tension steel reinforcement utilized in the section of the beam should be close to around 0.3 per cent

Normally, the depth of singly reinforced beams is design as that way so that the percentage of steel required is near around seventy-five per cent of balanced steel

Guideline 2

Minimum two reinforcement bars should be used as tension reinforcement steel, and also not more than six bars utilized in one layer in the beam section 

Guideline 3

The beam dimensions of hanger bars shouldn't be less than 10 mm and bar 12 mm. The diameters of bars generally used for beams are 10, 12, 16, 20, 22, 25 and 32 m. 

When different sized of bar utilized in one layer of beam section then place the largest diameter bars at the corner or near the beam faces. 

The per cent areas of reinforced steel should be symmetrical regarding to the centre line of the beam



Guideline 4

The width of the beam cross-section necessary for adaptable the required number of reinforcement bars will depend upon the given specification for minimum cover and minimum spacing

Indian standers IS CODE 456:2000: clause 25.4 give the required minimum cover to main steel bars for beam as 25 mm or diameter of bears, whichever is larger and 15 mm to the stirrup

These mean concrete cover value can be acceptable for most parts of India, but these should be increased by at least 5 to 10 mm for coastal areas of India, as explained in section 3.4

IS code 456:2000 clause 25.3.1 gives the details description guidelines for the minimum required distance between two bars as the diameter of bars or maximum size od aggregate plus 5 mm. The maximum size of aggregates generally used for any construction in India is 20 mm so that clear maximum distance between two reinforcement bars should be 25 mm. 

Accordingly, the minimum width for placement of steel can be easily worked out. Assuming the use of 8 mm steel as stirrups, the minimum width required for different steels are given in table 4.6


Guideline for determining width, depth & reinforcement of beam
Guideline for determining width, depth & reinforcement of beam
source: IS code 456:2000

Guideline 5

The depth of the beam should satisfy the deflection requirements with regard to L/d ratios

In addition, for the economy, the ratio of overall depth to width should be between 1.5 to 2.0


Guideline 6

In the T beams, the depth of the slab is generally used as about 20percent of the overall depth of the beam

Guideline 7

For main steel reinforcement bars in designing of the section, select only one size of bars or same for all bar if possible. 

In any case, limit the main bars to two sizes and that too without much variation in diameter the two

Guideline 8

The usual widths of beams adopted in mm are 150, 200, 230, 250 and 300. These widths should be equal to or less than the dimension of the columns into which they frame. 

as an example, 300 mm wide beams can frame into 300 mm or 400 mm dimensions of columns

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