Thier are various types of arches used in construction.
A structure constructed with the help of wedge-shaped bricks or stone joined together with a mortar forming the curve like portion over the opening to support the weight of the wall above it along with the other super-imposed loads is called as an arch.
Due to the wedge-shaped portion of bricks or stones, the units support each other and loads makes them more compact and possible to transmit the pressure downwards to their supports.
Different types of arches in houses:
In flat arches, the angle made by skewbacks is 60° with horizontal hence it makes an equilateral triangle with intrados as the base.
The intrados are actually flat but a slight rise of camber about 1 cm to 1.5 cm per meter width of the opening is given to the intrados, so to obtain the small settlements and extrados are kept horizontal.
Flat arches are suitable upto 1.5m for light loads.
Brick arches are mainly classified as rough brick arches, axed brick arches or rough cut brick arches, gauged brick arches and purpose-made brick arches.
We are going to study rough brick arches and axed brick arches as follows:
1.Rough brick arches:
When the arches are constructed without cutting the ordinary bricks into the shape of voussoirs then it is termed as rough brick arches.
In such arches, the joints are made wedge-shaped so as to obtain the arch curve with more thickness at the extrados and less thickness at intrados.
Because of more thickness at extrados and less thickness at intrados, the complete view of the arch is not so good looking or beautiful hence this arches is not used for exterior brick masonry work.
2.Axed brick arches:
In this type of arch, the brick axe is used to cut the bricks info wedge-shape.
Because of cutting the bricks into wedge-shape, the thickness of the joints is uniform or same along the radial line, which is not observed into rough brick arches.
Since bricks are cut to wedge-shapes are not finally dressed, the appearance of this arch is not a good looking or pleasant.
Stone arches types:
Stone arches are commonly used for stone and brick structures, door and window openings, porches, they are classified as follows:
In this type, arches are constructed with the rubble stones which are dressed by hammer and made roughly to required shape and size of the voussoirs.
When the stones are dressed completely to make them into proper shape and when such stones used in the construction of arches, it is termed as ashlar arches.
In this type of arch, wedge shape arch is accurately prepared.
Hard bricks cannot be used in such arch because it is more difficult to cut the hard bricks to the: accurate and precise wedge shape.
In the case of stonework, stones are dressed to a true wedge shape, sometimes bricks are specially made in a wedge shape.
These specially made bricks are termed as rubber bricks which are directly used in arch construction.
Semi-circular arches types:
In the semi-circular arch, the center lies on the springing line and curve so obtained is like a semi-circle.
In this type, skewback is horizontal hence load transferal to the abutment is completely in a vertical direction.
This type of arch is specially constructed to relieve the lintel from a load of masonry hence a timber lintel is required to place over the wider opening.
The brick relieving arch is generally constructed above the lintel, the size of the lintel due to provision of the relieving arch can be reduced.
Due to its shape, this type is termed as corbel arch.
The corbel arch in which each course is cantilevered or corbelled one over the other until the two symmetrical sides meet or intersect at point ‘O’.
It’s the primary type of arch used for buildings by which the center of arc lies under the springing line.
Within the segmental arch, the thrust transferred in inclined direction to the abutment.
Horse Shoe Arches:
Horse shoe arch is a horseshoe shape that curves more than a half-circle, it is generally considered for vastu provisions.
It is also known as Gothic arch.
In such arch, the circles of two arcs meet at the top, so a triangle is formed, it can be either isosceles or equilateral.
Venetian arches types:
It also has pointed arches but its crown is darker than that of the spring.
It has 4 centres, all situated on the springing line.
The arch is semi-circle shape and the remainder of the arch is just like the venetian arch.
It has three centre malls situated on the springing line.
It consists of a semi-circular arch with two vertical elements on the spring.
The middle of the arch is situated on the horizontal line through the highest of the vertical part.
An arch transmits a superimposed load to the pavement through friction between the surfaces of the voussoir and the cohesion of the mortar.