Important Point

## What Is Singly Beam?

**A singly beam is the beam which is provided with longitudinal reinforcement in the tension zone. Compressive forces are handled by the concrete section in the beam.**

## What Is Doubly Beam?

**The beams reinforced with steel in compression and tension zones are known as doubly reinforced beams. This kind of beam will be found essential when headroom consideration or architectural concern the depth of the beam is restricted.**

The beam with its restricted depth, if reinforced provided on the tension side only, it may not have sufficient moment of resistance to resist the bending moment.

By raising the quantity of steel in the tension zone, the moment of resistance cannot be increased indefinitely. Generally, the **moment of resistance can be increased by not more than 25% beyond** the balance moment of resistance by making the beam reinforced on the tension face.

Hence, to additional increase, the moment of resistance of a beam section of **unlimited dimensions, a doubly reinforced beam is provided.**

Also, read: What is Plum Concrete | Application | Mix Design | Methodology

## Based on Implanted Reinforcement

### Singly Reinforced Beam

Reinforcements are provided to oppose tensile** stresses due to shear and bending in beams for singly reinforced beam sections**. Practically, for singly reinforced beams, two additional bars are supplied in the compression face of the beam so that stirrups can be tied with bars easily. These extra reinforcements are of the nominal diameter of 8mm or 10mm.

### Doubly Reinforced Beam

When the depth of the section is restricted due to **reasons like, such as architectural reasons** or basement floors, the beam section is designed as a doubly reinforced concrete beam.

These bars shall** withstand in compressive stresses and are provided** with reinforcement in compression face.

Beams, when subjected to in torsion, are provided additional longitudinal and shear reinforcement to resist bending, and shear stresses developed due to torsion.

Also, read: Difference Between Mortar and Concrete | What Is Mortar & Concrete | Type of Mortar & Concrete

### Singly Reinforced Beam:

The beam, which is longitudinally reinforced only in** the tension zone, is known as a singly reinforced beam**. In Such beams, the decisive bending moment and tension due to that bending are carried by the reinforcement, while the concrete concedes the compression.

We take it Practically; it is not possible to make available reinforcement only in the tension zone, due to we need to tie the stirrups with it. Therefore, at that place, two rebars are utilized in the compression zone to fasten the stirrups, and the rebars work as false members just for the stirrups holder.34

The loads Handel by a beam are transferred to walls, columns, or girders, which then transfer the force to adjoining structural compression members.

### Procedure of Singly Reinforced Beam Design

Calculate the value of N by the given formula:

N= (mc)/(t+mc)

**Where N = Critical Neutral AxixConstant.**

Using this below method for Find the value of J.

J. =1- (N/3)

**Where J is known as Lever arm constant**

For Determine the moment of resistance coefficient

R=(1/2)JNc

Select appropriate breadth (b) and compare the bending moment and moment of resistance with the sufficient depth of that section.

d= sq root ([BM]/[Rb])

Calculate the value of At by the given formula

At = (BM)/(t.J.d)

**Where At = Area of tensile steel.**

**T = Allowable tensile stress in steel.**

For a particular Beam section,** It is necessary to give Reinforcement(Steel Bars)** in the Compression and Tension zone. If the reinforcement is only in tension zone, then it is called Singly Reinforcement Beam, and on another hand, if the reinforcement is in both the Tension and Compression zone, **then it is called a Doubly reinforced Beam.**

In both cases, there will be load in tension and compression zone. This is because; it is not possible to figure a Beam structure without stirrups.

To hold the stirrups in its standing position, it is necessary to place two reinforcements in the compression zone of singly reinforced Beam. However, those two will never carry or pass loads in its body, and it is just fake.

In a Beam, the topmost section is called the Compression zone, and the bottom part is called the Tension zone.

### Rcc Beams Info:

RCC beams are built-in cement concrete reinforced with using reinforced bars. Where Beams resist tensile and compression adds stiffness to the structure.

Beams generally manage vertical gravitational forces, but it can also be used to handle horizontal loads (i.e., loads placed due to wind and an earthquake ). The loads carry by the beam are moveable to walls, columns, or girders, which then transfer the force to adjoining structural compression members. In light-frame construction, the joists rest on the beam.

Also, read: What Is Cover in Concrete | Clear Cover in Beams, Slab, Column, Footing

### Doubly Reinforced Beam:

This article intends to discuss types of beam construction and RCC design of supported reinforced beam.

This doubly beam is also used in the following given situations;

The outsider live loads may alternate, I .e.it may occur on both faces of the member.

For example:

- A pile maybe pull up in that manner, the tension and compression zones may alternate in all case.
- The loading types may be eccentric, and the eccentricity of the load may be changeable from one side of the axis to the other side of the axis.
- The member may be intended to a shock or impact or accidental lateral thrust.

Also, read: Concrete Mix Ratio | What Is Concrete Mix Ratio | Type of Concrete Mix Ratio

### Procedure for the Doubly Reinforced Beam Is Given Below;

**Step 1**

calculate the moment of resistance(limiting) for the given cross-section (Mu lim) using the formula for singly reinforced beam

**Mu lim** **= 0.87.fy.Ast1.d [1 – 0.42Xumax]**

Or

for Balanced section in a beam

**Ast1 = (0.36Xumax.fck.b)/(0.87fy)**

**step 2**

factored moment **Mu** > **Mu** **lim**, then a doubly reinforced beam is necessary to be designed for an extra moment.

**Mu** – **Mu lim** = fsc.Asc (d – d’) [fsc value from code page no. 70]

**Step 3**

Additional area of tension steel Ast2

**Ast2 =Asc.fsc/0.87fy**

**Step 4**

Total tension steel Ast, **Ast = Ast1 + Ast2**

### Single Reinforcement Beam

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression.

### Singly Reinforced Beam and Doubly Reinforced Beam

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression. In singly reinforced beam compression, stress resists by the concrete, while in doubly reinforced beam compression steel, counters the compression stress.

### Double Reinforcement Beam

A reinforced concrete beam with steel reinforcement both in tension and compression zone is called a doubly reinforced beam.

### Singly and Doubly Reinforced Beam

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression.

### Tension and Compression Zone in Beam

**Compression is the opposite of tension**, so as one progresses down the beam from the top surface to the bottom, the compression stress gradually decreases to zero and then the stresses reverse, go into tension and gradually increase towards the bottom of the beam.

### Compression and Tension Zone in Beam

In a normal beam (simply supported) two zones generally arise, viz. **compression zone at top and tension zone at bottom**. As concrete is weak in tension, steel is introduced in the tension zone to take the tension, but as strength of concrete is ignored in tension zone with respect to compression zone.

### Beam Tension and Compression Zone

The part of concave face of beam which lies upward to the neutral axis and has to elongate compared to neutral axis therefore is called as beam tension zone

### Beam Compression and Tension Zone

In a normal beam (simply supported) two zones generally arise, viz. **compression zone at top and tension zone at bottom**. As concrete is weak in tension, steel is introduced in the beam tension zone to take the tension, but as strength of concrete is ignored in tension zone with respect to compression zone.

### Compression and Tension Reinforcement in Beam

**Compression is the opposite of tension**, so as one progresses down the beam from the top surface to the bottom, the compression stress gradually decreases to zero and then the stresses reverse, go into tension and gradually increase towards the bottom of the beam.

### Singly Beam and Doubly Beam

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression. In singly reinforced beam compression, stress resists by the concrete, while in doubly reinforced beam compression steel, counters the compression stress.

### What Is Singly Reinforced Beam?

The beam that contains steel reinforcement only in the tension zone refers to a singly reinforced beam.

### Why We Use Singly Reinforced Beam?

The singly reinforced beam is suitable **when the moment of resistance of the balanced reinforced concrete beam of dimension b × d is Rbd2**. Concrete has significant compressive strength and minor tensile strength.

### What Is Singly Reinforced Design?

**When the area of steel is provided in tension zone only i.e the reinforcement is given only in tension zone**, it will be known as singly reinforced beam. In singly reinforced beam, the reinforcement carries the ultimate bending moment and tension due to bending of the beam.

### Why Doubly Reinforced Is Used?

**It is impossible to increase the beam’s depth due to architectural or headroom restrictions**. To reduce the long term deflections due to shrinkage.

### Tension and Compression Bars in Beams

**Compression is the opposite of tension**, so as one progresses down the beam from the top surface to the bottom, the compression stress gradually decreases to zero and then the stresses reverse, go into tension and gradually increase towards the bottom of the beam.

### Doubly Reinforcement Beam

**A reinforced concrete beam with steel reinforcement both in tension and compression zone** is called a doubly reinforced beam. The compression reinforcement is provided to increase the load-carrying capacity of beams.

### Compression Bar in Beam

**The part of concave face of beam that lies below the neutral axis and shortens compared to neutral axis** is therefore called as compression zone.

### Tension Bars in Beams

Tension reinforced section is when you have steel reinforcement (rebar) on the tension controlled region where the rebar is used to counteract the lack of tensile strength in concrete. When reinforcement is only present in the tension zone, you have a singly reinforced beam

### Compression Reinforcement

In normal strength concrete, compression reinforcement **helps in reducing creep under sustained load in the compression zone**, and this helps in reducing the final deflection of the structure.

### Difference Between Singly Reinforced Beam and Doubly Reinforced Beam

**A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression**. In singly reinforced beam compression, stress resists by the concrete, while in doubly reinforced beam compression steel, counters the compression stress.

### Singly and Doubly Reinforced Beam Difference

**A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression**. In singly reinforced beam compression, stress resists by the concrete, while in doubly reinforced beam compression steel, counters the compression stress.

### What Is Singly and Doubly Reinforced Beam?

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression. In singly reinforced beam compression, stress resists by the concrete, while in doubly reinforced beam compression steel, counters the compression stress.

### What Is the Purpose of Doubly Reinforced Concrete?

**To increase the strength of the concrete beam**. To reduce long-term deflections of members. For minimum moment loading. For positioning stirrups (by tying them to the compression bars) and keeping them in place during concrete placement and vibration.

### Why Doubly Reinforced Beam Is Necessary?

Doubly reinforced beam is provided **to increase the moment of resistance of a beam having limited dimensions**. Minimum compression reinforcement is provided to hold the Shear Reinforcement (stirrups) in position and for increasing the ductility of beam.

### Tension Reinforcement in Beam

**Reinforcements shall be placed at the side of the beam that has tension**. For a simply supported beam, tension is at the bottom of the beam while for a cantilever end, tension is at the top of the beam. Shear is at its maximum at the edge of supports. Diagonal shear cracks are normally developed close to the support.

### Double Reinforced Beam

A reinforced concrete beam with steel reinforcement both in tension and compression zone is called a doubly reinforced beam.

### Tension Bar in Beam

Tension reinforced section is when you have steel reinforcement (rebar) on the tension controlled region where the rebar is used to counteract the lack of tensile strength in concrete. When reinforcement is only present in the tension zone, you have a singly reinforced beam.

### Compression and Tension Bars in Beams

**Compression is the opposite of tension**, so as one progresses down the beam from the top surface to the bottom, the compression stress gradually decreases to zero and then the stresses reverse, go into tension and gradually increase towards the bottom of the beam.

### In a Doubly Reinforced Beam

A doubly reinforced beam **increases the moment of resistance by providing steel in both tension and compression zone in the beam**. The depth of this type of beam is restricted to fulfill architectural requirements and building serviceability.

### Define Singly Reinforced Beam

**The beam that contains steel reinforcement only in the tension zone** refers to a singly reinforced beam. In this beam, reinforcement carries the tension force, while concrete has the compressive load caused by the deflection of the beam.

### Area of Steel in Compression Zone (Asc) Provided in

Reason of being uneconomical is as the steel in compression is under stressed to bear same compressive force the requirement of steel increases. as

- Force= stress * area of steel

keeping force constant

- Area of steel= c/stress as stress deceases the area increases as they are inversely proportional.

### Why Is Doubly Reinforced Beam Provided?

**It is not possible to increase the depth of the beam due to architectural or headroom restrictions**. To reduce the long term deflections due to shrinkage.

### Double Reinforcement Beam Design

Design steps for a doubly reinforced beam section are as follows.

**Step 1:**Calculate the depth of neutral axis. Apply the equilibrium condition for the beam section.**Step 2 :**Calculate the factored moment. In this case, we split the total bending moment into two component.**Step 3 :**Design of compression reinforcement.

### Compression Reinforcement in Beams

The compression reinforcement is provided to increase the load-carrying capacity of beams. It is possible to increase the moment-carrying capacity of the beam by increasing its dimension.

### Singly Supported Beam

The beam that is longitudinally reinforced only in tension zone, it is known as singly reinforced beam. In Such beams, the ultimate bending moment and the tension due to bending are carried by the reinforcement, while the compression is carried by the concrete.

### Singly Reinforced Beam

**The beam that contains steel reinforcement only in the tension zone** refers to a singly reinforced beam. In this beam, reinforcement carries the tension force, while concrete has the compressive load caused by the deflection of the beam.

### When Do We Use Doubly Reinforced Beam?

This type of beam is mainly provided **when the depth of the beam is restricted**. If a beam with limited depth is reinforced on the tension side only it might not have sufficient resistance to oppose the bending moment. In order to increase the moment carrying capacity of the section.

### Why We Use Doubly Reinforced Beam?

Doubly reinforced beam is provided to increase the moment of resistance of a beam having limited dimensions. Minimum compression reinforcement is provided to hold the Shear Reinforcement (stirrups) in position and for increasing the ductility of beam.

### Singly Reinforced and Doubly Reinforced Beam

For a Beam, It is necessary to provide Reinforcement(Steel Bars) in Compression and Tension zone. In a beam, If the reinforcement is only in tension zone, then it is called Singly Reinforcement Beam, and if the reinforcement is both at Tension and Compression zone then it is called Doubly reinforced Beam.

In both cases, there will be a rod in tension and compression zone. This is because, it is not possible to form a Beam structure without stirrups. To hold the stirrups in a standing position, it is necessary to place two reinforcements in compression zone of singly reinforced Beam.

### Doubly Reinforcement

A reinforced concrete beam with steel reinforcement both in tension and compression zone is called a doubly reinforced beam.

### In a Singly Reinforced Beam

Plane sections transverse to the centre line of the beam before bending remain plane after bending.

### Why Doubly Reinforced Beam Is Required?

Doubly reinforced beam is provided **to increase the moment of resistance of a beam having limited dimensions**. Minimum compression reinforcement is provided to hold the Shear Reinforcement (stirrups) in position and for increasing the ductility of beam.

### Compression Reinforcement in Beam

From the practical aspects of consideration, therefore, the minimum steel as compression reinforcement should be at least 0.4% of the area of concrete in compression or 0.2% of the whole cross-sectional area of the beam so that the doubly reinforced beam can take care of the extra loads in addition to resisting the effects of creep and shrinkage of concrete.

### Tension Zone and Compression Zone in Beam

**Compression is the opposite of tension**, so as one progresses down the beam from the top surface to the bottom, the compression stress gradually decreases to zero and then the stresses reverse, go into tension and gradually increase towards the bottom of the beam.

### Why Doubly Reinforced Beam Is Used?

The beam that is longitudinally reinforced only in tension zone, it is known as singly reinforced beam. In Such beams, the ultimate bending moment and the tension due to bending are carried by the reinforcement, while the compression is carried by the concrete.

### Doubly Reinforced Beam Design

The step by step procedure to design a doubly reinforcement beam as per IS:456:2000 is as follows:

- Step 1: Calculate the depth of neutral axis.
- Step 2 : Calculate the factored moment
- Step 3 : Design of compression reinforcement

### Tension Reinforcement in Beam Formula

Here, the tension reinforcement in beam formula are as follows.

**[Ast/bd]=[0.85/fy]**

### Singly and Doubly Reinforced Section

A Singly reinforced beam holds a steel bar in the tension zone, but in doubly reinforced beams, steel bars are given in both zones, tension, and compression.

### Advantages of Singly Reinforced Beam

Concrete has significant compressive strength and minor tensile strength. So In a singly reinforced beam, steel is given in the tensile zone, which is good in tension and compression. Singly reinforced beam has a limited moment of resistance with specified width and depth grade of concrete and steel.

### Doubly Reinforced Beam Are Provided When

Doubly reinforced beam is provided **to increase the moment of resistance of a beam having limited dimensions**. Minimum compression reinforcement is provided to hold the Shear Reinforcement (stirrups) in position and for increasing the ductility of beam.

### Tension and Compression Reinforcement

Tension reinforced section is when you have steel reinforcement (rebar) on the tension controlled region where the rebar is used to counteract the lack of tensile strength in concrete.

### Tension Side of Beam

The deflection in the beam causes two things to happen: The top surface of the beam is compressed and tries to get shorter, and **the bottom surface** is in tension and tries to get longer.

### Compression Zone in Beam

Tension zone and compression zone in simply supported beam and the at the same time upper portion of the beam is compressed and pulled inside causing compression in the upper portion of the beam that’s known as compression zone of the beam.

### RCC Singly Reinforced Beam Design

Singly Reinforced Beam Design Procedure Are As Following: Determine the value of N by the following formula:** N = mc/t+mc 2**. Find the lever arm constant.

### Tension Zone in Beam

The part of concave face of beam which lies upward to the neutral axis and has to elongate compared to neutral axis therefore is called as tension zone.

### Doubly Reinforced Beam Diagram

### Single Reinforcement and Double Reinforcement

A beam that is reinforced in the tension zone only is called a singly reinforced concrete beam, whereas a doubly reinforced concrete beam is reinforced on both tension and compression faces.

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