What is Lintel?
A lintel is a horizontal structural member that is provided above the openings such as windows, doors, etc., in a building. Lintel is also used to support projections like sunshades and lofts. The width of the lintel is generally same as that of the wall. In this article, different types of lintels and their uses are discussed.
Functions Of Lintel:
1. It should take care of the load from the masonry above the openings.
2. A Lintel is an important flexural member that must be designed in such a way that it can resist the tension, compression and shear acting on it.
3. The lintel should also counterattack deflection.
How To Calculate Loads Acting On Lintels?
The load acting on the lintel shall be calculated by two ways:
1. Conventional lintel loading
2. Thin lintel loading
1. Conventional Lintel Loading:
The load of the masonry wall above the lintel is calculated as a triangular load. An imaginary equilateral triangular load of angle 60 degrees is used to calculate the load acting on the lintel as shown in the figure.
2. Thin Lintel Loading:
A relatively thin layer of steel is provided below the brickwork. This layer of steel along with the bricks above it acts as composite structure. The bricks are good in compression but weak in tension. The tension is resisted by the steel provided in the beam. Here the load is taken in a rectangular fashion. An imaginary rectangular load of intensity of 5 brick courses or 45 cm is taken as the load acting on the lintel member.
Types Of Lintels:
Lintels can be classified based on two criteria:
a) Classification Based On Span:
1. Lintel beam or Cut lintel
2. Lintel band or Continuous lintel
1. Lintel Beam Or Cut Lintel:
In this type, the lintel beam is provided only above the openings. These lintel beams can be precast or cast in place. Bearings are provided to make sure the load is transferred properly to the frames of the doors and windows. These types of lintels are very popular in load bearing structures. The width of the bearing is the minimum of the following:
1. 10 cm
2. Height of the lintel beam
3. 1/10th to 1/12th of the span of the lintel
2. Lintel Band Or Continuous Lintel:
This lintel runs throughout the span of the building. It is like another tie beam connecting all the columns of the structure. It is mostly made up of reinforced cement concrete. This types of lintels are suitable in
1. Framed structures.
2. Buildings with expansive soils.
3. Areas prone to earthquakes.
b) Classification Based On Materials:
According to the type of material used for construction, lintels can be classified into the following:
1. Timber lintels.
2. Flitched lintels.
3. Stone lintels.
4. Brick lintels.
5. Steel lintels.
6. Plain cement concrete lintels.
7. Reinforced Cement Concrete lintels.
1. Timber Lintel:
Timber lintels are made of natural wood mainly Redwood. This is one of the oldest types of lintels to have been constructed by man. A well-seasoned wood that is hard and sound must be used for construction. The depth of the lintel is usually 1/12th of the span of the lintel. A single plank of wood may be used or two or more strips of wood may be joined together with the help of bolts and be used as a built-up system.
Advantages Of Timber Lintel:
a. Easy to construct
b. Can be used to temporary structures
c. No form work is needed
d. No curing period is required.
Disadvantages Of Timber Lintel:
a. Wood may decay if not maintained properly
b. It is very costly than the other alternatives available
c. It is vulnerable to fire
d. Wood is not very strong to take care of the tension, compression and shear forces that are acting on the lintel
2. Flitched Lintel:
Flitched lintels are modified timber lintels. If steel plates are provided at the top and bottom of the timber lintels, then it acts as a composite structure – the flitched lintel.
Advantages Of Flitched Lintel:
a. Easy to construct.
b. Very strong when compared to timber lintels.
c. No formwork is needed.
d. No curing period is required.
Disadvantages Of Flitched Lintel:
a. It is very costly than the other alternatives available.
b. Both steel and timber are vulnerable to fire.
3. Stone Lintel:
Stone lintels are made of stones of height at least 15 cm. Mostly a single stone is preferred to avoid weak areas such as joints in the stones.
Advantages Of Stone Lintel:
a. It provides a very pleasing sight and an elegant appearance.
b. It is very cheap if the stones are locally available.
c. Ideal for short spans.
d. No need for formworks and curing.
Disadvantages Of Stone Lintel:
a. It is very weak in tension.
b. It does not perform well under vibrations, earthquakes and shock waves
c. It can be costly if it is not available locally
d. It cannot be used for long spans
4. Brick Lintel:
Brick lintels are made up of well burnt bricks. The height of the lintel ranges from 10 cm to 20 cm depending on the span and the loading.
Advantages Of Brick Lintel:
a. It is the cheapest of all the lintels.
b. Ideal for short spans.
c. Since both the lintel and masonry are made of the same material, the thermal coefficient of both the members are same. Therefore, cracks due to thermal stresses can be avoided.
Disadvantages Of Brick Lintel:
a. Bricks are not very strong for acting as a lintel.
b. Bricks are weak in tension.
c. Only light loads can be taken by brick lintels.
d. It is not suitable for long spans.
e. Formworks are necessary to support the bricks during construction.
f. A curing period of minimum 2 to 3 weeks is necessary.
5. Steel Lintel:
Steel lintels are made using prefabricated GI sheets, rolled I sections or angle sections. If more than one section is used, a pipe separator may be used to maintain the minimum distance between the sections.
In addition to this, the steel sections may be embedded into the concrete to increase the resistance to fire and other environmental conditions like corrosion. Else, the steel sections should be painted with anti-corrosive paints.
Advantages Of Steel Lintel:
a. It can be used for long spans.
b. Steel is light thus it is very easy to handle and transport.
c. Steel is versatile and can be fabricated to any shape.
d. The prefabrication of steel fastens the process of construction.
e. No curing or formwork is needed.
Disadvantages Of Steel Lintel:
a. It is vulnerable to corrosion.
b. It is susceptible to fire.
6. Plain Cement Concrete Lintel:
The plain cement concrete lintels are similar in behaviour to the stone lintels. They are very good in compression but weak in tension.
Advantages Of PCC Lintel:
a. Ideal for short spans.
b. It is relatively cheap.
c. It is easy to construct.
d. It is very convenient is a prefabricated PCC lintel is used
Disadvantages Of PCC Lintel:
a. It is very weak in tension.
b. It cannot be used for long spans.
c. It does not perform well under vibrations, earthquakes and shock waves.
d. Formworks are necessary to support the concrete during construction if it is cast in site.
e. A curing period of minimum 28 days necessary if it is cast in site.
7. Reinforced Cement Concrete Lintel Or RCC Lintel:
The reinforced lintels have steel rods provided inside the concrete on the bottom to take care of the tension. Sufficient cover is provided to prevent the rusting of the reinforcements. Shear reinforcements can also be provided to take care of the shear forces.
The types of RCC lintels are as follows:
1. Cut lintel: It is a lintel beam spanning only over the openings. Mostly a precast lintel beam is used. It is common in load bearing structures.
2. Band lintel: It is used in framed structures as a tie beam connecting all the columns in a structure. It spans over the length of the building like a regular beam but above the openings.
3. Lintel with projections: This type of lintel is used to support the sunshades and lofts.
Advantages Of RCC Lintel:
a. It is the best of all lintels to satisfy all the design requirements such as resistance to tension, compression, shear, and deflection.
b. Precast RCC lintels can speed up the construction process.
c. It can be provided for long spans.
d. It is relatively cheap for the design requirements it satisfies.
e. It is easy to construct.
Disadvantages Of RCC Lintel:
If it is cast in the site,
a. Formworks are necessary to support the concrete during construction.
b. A curing period of minimum of 28 days necessary.
Special Types Of Lintels:
RCC Boot Lintel:
An RCC boot lintel is provided for cavity walls. This lintel is not uniform in cross-section. The height of the lintel is reduced toward the outside edge. This gives a pleasant appearance to the lintel and also the amount of concrete used is also reduced. Since cavity walls are vulnerable to water penetration, they are protected by providing a dampening coat.
The post What Is Lintel? Types Of Lintels And Their Uses In Building appeared first on Daily Civil.