What are the guidelines for determining the width, depth, and reinforcement of a beam?
The following Top 8 guidelines for beams 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 percent
Normally, the depth of singly reinforced beams is designed that way so that the percentage of steel required is near around seventy-five percent of balanced steel
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Guideline 2
Minimum of 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 bars are utilized in one layer of beam section then place the largest diameter bars at the corner or near the beam faces.
The percent areas of reinforced steel should be symmetrical regarding the centerline of the beam
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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 gives 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 values 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 of 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 the placement of steel can be easily worked out. Assuming the use of 8 mm steel as stirrups, the minimum width required for different steels is given in table 4.6
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| Guideline for determining width, depth & reinforcement of beam source:Â 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 the designing of the section, select only one size of bars or the same for all bars if possible.
In any case, limit the main bars to two sizes and that too without much variation in diameter of 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
