Arches arches arches

ARCHES

• ARCH• An arch is a structure that spans a

space while supporting weight(e.g. a doorway in wall, windows, ventilators, opening). Arches appeared as early as the 2000 BC in Mesopotamia brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.

• The arch supports a vertical load primarily by axial compression of its wedge-shaped voussoirs

• PIER:

• Pier is a solid block of masonry supporting an arch. They are often made of stone, but those serving as primary support for large arches are usually made of concrete

1.TECHNICAL TERMS:

• FOUNDATION:

• The foundation is a large stone that is set into the ground. The piers are then built on top of it. It transfers the weight of the arch to the soil in the ground.

1.TECHNICAL TERMS:(continue…)

• IMPOST:

• An impost is the topmost part of an architectural column. Also called an abacus, it is usually a flat piece of stone. It can be carved or decorated



CENTRE: This is the midpoint of the circle which describes the curve of the arch (b). CROWN: This is the portion of the arch which forms the top of the curve (c). EXTRADOS: The outer curved line of an arch, or the upper surface of the arch stones(d). HAUNCH: The flanks of an arch, the sides of the curve (e). INTRADOS: The under surface or soffit of an arch (f). KEYSTONE: The central wedge-shaped arch stone at the crown of an arch (g), which is the last stone to be put in place. RADIUS: The straight line (h) from the centre of an arch to any point on its intrados (the shorter radius, r); or to any point on its extrados (the longer radius, R).

• SPRINGING LINE: • The line across the arch which would connect

the springing points (j). • RISE:• The height of an arch measured

perpendicularly from the springing line to the highest point of the intrados (k).

• SPRINGER: • The first stone laid in an arch on either side

(1). • SKEWBACK:• That portion of the abutment which directly

supports the springers (m). It is so called because the surface slopes towards the opening.

• SPAN: • The horizontal distance between the springing

points (n); the length of the springing line. • CAMBER:• This is the space between the springing line

and the intrados (o). • ARCHSTONES: • These are any of the stones or blocks which

form the arch itself.


2. TYPES OF ARCHES

The various arches types are classified as:

A. Classification of arches according to shape.

B. Classification of arches according to numbers of centers.

C. Classification of arches according to workmanship.

D. Classification of arches according to materials of construction.

2. TYPES OF ARCHES (continue……)



Flat Arch:

an arch with mutually

supporting voussoirs that

has a straight horizontal

extrados and intrados.

Usually the skewback forms

an angle of 60 degree.


Segmental Arch:

The centre of arch is situated

below the springing line. In this

arch type the curve is a less

than semicircular segment of a

circle



Semi Circular Arch:

The centre of the arch lies on the

springing line and the shape of

curve of an arch is a semicircular.

It is drawn from a single center




Semi Elliptical Arch:

This arch has more than one centre and its shape is that of a semi ellipse.



Inverted Arch:

An arch with the crown

downward, below the line of the

springing; commonly used in

tunnels and foundations. Also

known as inflected arch. This

arch is constructed to increase

the bearing power of the soil.



Pointed Arch:

This type of arch consists

of two curves which meet

at the apex of the triangle.

This triangle formed may

be equilateral or isosceles.

The centers of the arch

may be above or below the

springing line and they may

be in between or outside

the springing line



Relieving Arch:

An arch, usually segmental and

often a blind arch, built above

the lintel of a door or window to

discharge the weight of the wall

above the lintel to each side.



Horse-shoe Arch:

The horseshoe arch,

also called the Moorish

arch and the Keyhole

arch, is the arch of

Islamic architecture.

Formed in the shape

of a horseshoe.


Stilled Arch:

It consists of a semi-

-circular arch attached at

the top of two vertical

imposts.

Springing line of the arch

passes through the top of

vertical imposts.




Venetian Arch:

In this type of arch, the depth at

crown is more than that at the

springing line. The venetian

arch has four centers.



Florentine Arch:

This type of arch is similar to

the venetian arch except that

the intrados has the shape of a

semi-circular curve, there are

three centers for this type.

IN NEXT CLASS


B. Classification of arches according to the numbers of centers.

• One centered Arch

• Two centered Arch

• Three centered Arch

• Four centered or Tudor Arch

• Five centered Arch



One centered Arch

This type of arch has one

center only . Flat, segmental,

semicircular, horse-shoe and

stilled arches are one

centered . Sometimes circular

windows are used to have an

architectural effect. For this

purpose a bull’s eye arch is

adopted.


Two centered Arch

This type of arch has

two center. A pointed

arch is a good

example of this type.



Three centered Arch


three centers. It is in

the form of semi-

ellipse. The other

example of this type is

Florentine arch.



Four centered or Tudor Arch

This type of arch has four

centers. It consists of two

different curves and has the

appearance of an ellipse at the

haunches. The venetian arch is

the good example of this type.



Five centered Arch


got five centers and its

look like a semi-

elliptical arch.


• Rough Arch

• Axed or Rough cut Arch

• Gauged Arch

C.Classification of arches according to workmanship.




Rough Arch

This type of arch is constructed

from ordinary uncut bricks. As the

bricks are rectangular in shape,

mortar joints become wider at the

extrados than at the intrados. A

rough arch is used where

appearance is of secondary

importance.



Axed or Rough cut Arch

This type of arch is

constructed from bricks

which are cut to a wedge-

shape by means of an

axe. The bricks are rough-

axed or fine axed.

Gauged Arch

This type of arch is constructed

from bricks which are finely cut

by means of wire saw. The

surfaces of bricks are finished

with a file. This arch is used

where a fine finish of the surface

is required. The mortar joints are

thin as 1.50 mm to 0.75 mm.





• Brick Arch• Stone Arch

• Concrete Arch• Metal Arch

• Timber Arch

•THE END

Brick Arch



Stone Arch



Concrete Arch



Timber Arch



Metal Arch



Arches arches arches

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