Lintels and archesLintels and arches

LINTELLINTEL It is a beam-like horizontal structural It is a beam-like horizontal structural

flexural member,used to span over flexural member,used to span over the openings of doors,windows and the openings of doors,windows and cup-boards.lintel bahaves just like cup-boards.lintel bahaves just like beam.it provides a bearing for the beam.it provides a bearing for the masonry above the openings and masonry above the openings and transfers all the loads acting over the transfers all the loads acting over the opening to the supporting walls.opening to the supporting walls.

Classification of lintelsClassification of lintels There can be only one classification of There can be only one classification of

lintel and that is according to the lintel and that is according to the materials used in their materials used in their construction.lintels may beconstruction.lintels may be

1)Timber lintel1)Timber lintel

2)stone lintel2)stone lintel

3)brick lintel3)brick lintel

4)reinforced brick work lintels4)reinforced brick work lintels

5)steel lintel5)steel lintel

6)R.C.C lintel6)R.C.C lintel

7)thin lintel7)thin lintel

Timber or wooden lintel:Timber or wooden lintel: In old days when technology was not much In old days when technology was not much

advanced,timber lintels were very advanced,timber lintels were very commonly in use.but now a days commonly in use.but now a days availability of timber has become difficult availability of timber has become difficult and costly.and costly.

They are combustible and hence not They are combustible and hence not recommended for use in fireproof recommended for use in fireproof constructions.minimum depth of the constructions.minimum depth of the wooden lintel should be 7.5cm. Timber wooden lintel should be 7.5cm. Timber lintels are comparitively weak.lintels are comparitively weak.

Stone lintelStone lintel Stone lintels are very common in use in Stone lintels are very common in use in

regions where stone is easily regions where stone is easily available.they may be used in form of available.they may be used in form of single-piece or more than one piece.stone single-piece or more than one piece.stone lintels are very weak in tension and lintels are very weak in tension and thus,cannot be used on large spans.thus,cannot be used on large spans.

Brick lintelsBrick lintels

Brick lintels are made by using first class Brick lintels are made by using first class bricks either laid on end or on edge. bricks either laid on end or on edge. They are suitable for small They are suitable for small spans not exceeding 90cm.for the spans not exceeding 90cm.for the construction of this lintel a temporary construction of this lintel a temporary timber support known as turning piece is timber support known as turning piece is constructed first. constructed first. For larger spans and heavy loads this For larger spans and heavy loads this lintel should not be used.in that case, lintel should not be used.in that case, reinforced brick lintel may be used.reinforced brick lintel may be used.

Reinforced brick work lintelReinforced brick work lintel When brick lintels have to be used over large When brick lintels have to be used over large

spans,they are reinforced with steel spans,they are reinforced with steel bars.bricks are arranged in such a way that bars.bricks are arranged in such a way that 2cm to 4cm wide,lengthwise,spaces are left 2cm to 4cm wide,lengthwise,spaces are left in the brick rows.steel rods are put in these in the brick rows.steel rods are put in these gaps and spaces are then filled with rich gaps and spaces are then filled with rich cement mortar or concrete. cement mortar or concrete. If the gap is about 20mm If the gap is about 20mm wide rich cement is used.if the gap is about wide rich cement is used.if the gap is about 40mm,it should be filled withcement 40mm,it should be filled withcement concrete.concrete.

The depth of the lintel should be minimum The depth of the lintel should be minimum 100mm.100mm.

Steel lintelSteel lintel Steel lintels may be made from angle Steel lintels may be made from angle

irons or rolled steel joists.angle irons are irons or rolled steel joists.angle irons are used for small spans and light loads used for small spans and light loads whereas rolled steel joists are used for whereas rolled steel joists are used for heavy loads and large spans. Rolled steel heavy loads and large spans. Rolled steel joists may be used singly or in group of joists may be used singly or in group of more than one joist. The more than one joist. The joists may be painted and left open.but if joists may be painted and left open.but if building is to be rendered fire-proof the building is to be rendered fire-proof the joists should be embedded in concrete.joists should be embedded in concrete.

R.C.C lintelR.C.C lintel

This is the lintel which has partially This is the lintel which has partially replaced all other types of lintels. replaced all other types of lintels. this lintel is this lintel is durable,strong,corrosion resistant,and durable,strong,corrosion resistant,and fire resistant. It is fire resistant. It is economical than all other lintels and economical than all other lintels and easy to construct. easy to construct. It can be used for any span and any It can be used for any span and any load.load.

Arch Arch Like lintel,arch is also a measure of Like lintel,arch is also a measure of

covering or bridging over the openings of covering or bridging over the openings of doors,windows etc.left in the masonry doors,windows etc.left in the masonry walls.walls.

It consists of arranging wedge shaped It consists of arranging wedge shaped stone blocks or bricks mechanically,in the stone blocks or bricks mechanically,in the form of circular,elliptical or any other form of circular,elliptical or any other form of ring over the openings.form of ring over the openings.

Wedge shaped blocks are joined Wedge shaped blocks are joined generally with rich mortar or lime mortar.generally with rich mortar or lime mortar.

Arches of cement concrete,R.C.C. and Arches of cement concrete,R.C.C. and steel are not built in wedge-shaped units steel are not built in wedge-shaped units but in form of a single unit.but in form of a single unit.

Arches can be classified in the following ways:Arches can be classified in the following ways:1)based on shape1)based on shape2)based according to number of centres2)based according to number of centres3)based on type of workmanship3)based on type of workmanship4)based on materials of construction4)based on materials of construction

Classification based on shapes:Classification based on shapes: Flat arch:Flat arch: It is constructed from specially cut blocks or It is constructed from specially cut blocks or

stones.stones. All the joints are made to radiate from one All the joints are made to radiate from one

common point.common point. The skew back is sloped at an angle of 60 The skew back is sloped at an angle of 60

degrees with the horizontal.degrees with the horizontal. This arch is weak type of arch and mostly used This arch is weak type of arch and mostly used

for face work.for face work.

Segmental arch:Segmental arch: In this arch,segment is smaller than the In this arch,segment is smaller than the

semicircle.the centre of this arch is situated semicircle.the centre of this arch is situated below the springing line.below the springing line.

Semicircular arch:Semicircular arch: In this arch length of arch is equal to the In this arch length of arch is equal to the

semicircle.centre of the arch lies on the semicircle.centre of the arch lies on the springing line of the arch.springing line of the arch.

Inverted arch:Inverted arch: this arch may be segmental,semicircular or of this arch may be segmental,semicircular or of

any other shape.it is constructed inverted or any other shape.it is constructed inverted or with extrados downward and intrados upward.it with extrados downward and intrados upward.it is constructed to increase the bearing power of is constructed to increase the bearing power of the soil.the soil.

Pointed arch:Pointed arch: This arch consists of two curves meeting at This arch consists of two curves meeting at

the apex of a triangle.the apex of a triangle. The triangle formed may be equilateral or The triangle formed may be equilateral or

isosceles.isosceles. In case triangle formed is In case triangle formed is

equilateral,centres of the curves will lie at equilateral,centres of the curves will lie at springing points.springing points.

In the case of isosceles triangle arch In the case of isosceles triangle arch centres of curves are not at the springing centres of curves are not at the springing points.points.

Semi-elliptical arch:Semi-elliptical arch: This arch has more than one centre and its This arch has more than one centre and its

shape is that of semi-ellipseshape is that of semi-ellipse..

Relieving arch:Relieving arch: This arch is used to relieve weak lintel or This arch is used to relieve weak lintel or

flat arch from the load coming on it.flat arch from the load coming on it. Shape of this arch may be segmental or Shape of this arch may be segmental or

semi-circular.semi-circular. The ends of relieving arch should be kept The ends of relieving arch should be kept

sufficiently inside the solid wall and there sufficiently inside the solid wall and there should be enough cover beyond the ends should be enough cover beyond the ends of the lintel.of the lintel.

Horse-shoe arch:Horse-shoe arch: This arch has centre above the springing This arch has centre above the springing

line of the arch.this arch is longer than line of the arch.this arch is longer than semicircle.semicircle.

Stilled arch:Stilled arch: It consists of a semi-circular arch attached at It consists of a semi-circular arch attached at

the top of two vertical posts.the top of two vertical posts. Springing line of the arch passes through the Springing line of the arch passes through the

top of vertical posts.top of vertical posts.Venetian arch:Venetian arch: Depth of arch at crown is more than at the Depth of arch at crown is more than at the

springing line.this arch has four centres.springing line.this arch has four centres.Florentine arch:Florentine arch: This arch has intrados in shape of a semi-circle This arch has intrados in shape of a semi-circle

but its extrados comprise of three centres.but its extrados comprise of three centres.Drop arch and Gothic arch:Drop arch and Gothic arch: Both these arches are similar to isosceles Both these arches are similar to isosceles

arch with little bit of difference in centres arch with little bit of difference in centres of both the curves.of both the curves.

Classification based on Classification based on number of centresnumber of centres

One-centered arch:One-centered arch: This arch has only one This arch has only one

centre.semicircular arch, segmental arch centre.semicircular arch, segmental arch and horse-shoe arch are all examples of and horse-shoe arch are all examples of one-centred arch.one centred arch may one-centred arch.one centred arch may be equal to full length of the circle also.be equal to full length of the circle also.