Design of Singly reinforced Sections | Method 1
In our article series for Singly reinforced sections, we have covered the following:
- Basic definitions and formulas
- Understanding stresses and modular ratios
- Assumptions for singly reinforced sections
- Design procedure for Singly reinforced section – I
- Solved Numericals for Singly reinforced beam | Method I
- Design of Singly reinforced sections | Design Method 2
- Solved Numericals for Singly reinforced beam | Method 2
- Moment of Resistance for Singly reinforced sections
- Solved numerical example | Moment of resistance
- Solved numerical example 2 | Guide to singly reinforced sections
Numerical Problem
An RC beam 200mm wide has an effective depth of 350mm. The permissible stresses in concrete and steel are 5N/mm2 and 140 N/mm2 respectively. Find the depth of neutral axis, area of steel and percentage of steel. (modular ratio (m) = 18.66)
Step One:
Given that:
b = breadth of a rectangular beam = 200mm
d = effective depth of a beam = 350mm
x = depth of neutral axis below the compression edge = ?
Ast = cross-sectional area of steel in tension = ?
σcbc = permissible compressive stress in concrete in bending = 5N/mm2
σst = permissible stress in steel = 140 N/mm2
m = modular ratio = 18.66
From the concrete stress diagram, the formula is given as,
σcbc/(σst/m) = x/(d – x)
5/(140/18.66) = x/(350-x)
Therefore, x = 139.97mm