# Singly Reinforced Beam

## Example 02: Finding the Number of 28-mm Steel Bars of Singly-Reinforced Concrete Cantilever Beam

**Problem**

A reinforced concrete cantilever beam 4 m long has a cross-sectional dimensions of 400 mm by 750 mm. The steel reinforcement has an effective depth of 685 mm. The beam is to support a superimposed load of 29.05 kN/m including its own weight. Use *f’ _{c}* = 21 MPa,

*f*= 165 MPa, and

_{s}*n*= 9. Determine the required number of 28 mm ø reinforcing bars using Working Stress Design method.

## Example 01: Total Compression Force at the Section of Concrete Beam

**Problem**

A rectangular reinforced concrete beam with width of 250 mm and effective depth of 500 mm is subjected to 150 kN·m bending moment. The beam is reinforced with 4 – 25 mm ø bars. Use alternate design method and modular ratio *n* = 9.

- What is the maximum stress of concrete?
- What is the maximum stress of steel?
- What is the total compressive force in concrete?

## Example 01: Required Steel Area of Reinforced Concrete Beam

**Problem**

A rectangular concrete beam is reinforced in tension only. The width is 300 mm and the effective depth is 600 mm. The beam carries a moment of 80 kN·m which causes a stress of 5 MPa in the extreme compression fiber of concrete. Use *n* = 9.

1. What is the distance of the neutral axis from the top of the beam?

2. Calculate the required area for steel reinforcement.

3. Find the stress developed in the steel.

## Design of Steel Reinforcement of Concrete Beams by WSD Method

Steps is for finding the required steel reinforcements of beam with known *M _{max}* and other beam properties using Working Stress Design method.

Given the following, direct or indirect:

*b*

Effective depth =

*d*

Allowable stress for concrete =

*f*

_{c}Allowable stress for steel =

*f*

_{s}Modular ratio =

*n*

Maximum moment carried by the beam =

*M*

_{max}