Design Methods for Singly reinforced Sections

Singly reinforced sections | Design of RCC structures

Earlier we discussed some basic terms in reference to singly reinforced sections design. It is important that you are thorough with the basic definitions and have complete understanding of stresses in concrete and steel. You should also possess the knowledge of reinforcement and terminology of beams which includes understanding singly reinforced beam, doubly reinforced beam, under reinforced beam, over reinforced beam and balanced reinforced beam.

There are two methods for the design of singly reinforced sections. In this article we will discuss the first method of singly reinforced section in a stepwise manner. The discussion will include the method for determining the value of neutral axis followed by a formula for the area of steel calculations.


b = breadth of a rectangular beam

d = effective depth of a beam

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

σst = permissible stress in steel

m = modular ratio

Neutral axis

Neutral axis is denoted as NA.

There are two methods for determining the neutral axis depending on the data given.


Stress strain diagram - Singly reinforced section
Stress strain diagram

In this article, we will discuss the first method followed by a couple of numericals for your understanding and then move on to the second method.

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Consequences of Wrong Structural Design | RCC Structures

A lesson for all the Civil Engineers and Designers to learn

I got a project of designing (Architectural Design) a Hostel in Lucknow, India. The Structural design that is, column positions and wall construction was already done. The client wanted me to design a Hostel keeping the column positions and exterior wall construction intact. I have written this article to address all the Civil engineering students as well as Civil Engineers to avoid making such blunders while they design. Please do read this article because understanding the intensity of the job of a Civil Engineer is must for every student and professional. I guess this realization has been washed away and forgotten in the wave of commercialism.

Hostel Design, Lucknow, India

The client mailed me the layout of the existing construction. After I studied the layout, I figured out that the Column layout was pathetic. I wonder what kind of Civil Engineer must have made the layout or if at all any Civil Engineer has done it.

Errors in Construction

Wrong size of the Columns

The size of the columns was 9”x9” and the building is supposed to be constructed upto G+2 floors which is really disastrous for the structure.

It could lead to structural failure and ultimately structural collapse.

(The duty of the Civil Engineer is to understand and not make such dramatic blunders. The consequences of this kind of structural design could be disastrous.)

Column layout and Exterior wall Construction
Column layout and Exterior wall Construction

9”x9” size columns are only preferred if you were to construct only a ground floor structure using M15 grade concrete. If you are to construct another floor that is (G+1), the minimum size of the column should not be less than 9”x12” using M15 grade concrete.

If the client insists on using smaller columns (9”x9”); in that case, use of M20 grade concrete should be done mandatorily and the construction should not be initiated before the client agrees to do so.

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