Arch,Terminology,Classification

1. TYPE OF ARCHES
Ankit Shukla
ACA,Agra

2. ARCH
What is an Arch?
 An Arch is a structure constructed of
wedge-shaped unit.
 It spans an opening to support the
weight of the wall and other
superimpose load.
B.C.Punmia
Google.com
Reference-

3. Terminology
1. Intrados:- This is an inner curve
of an arch.
2. Extrados:- Outer Curve of an
arch
3. Soffit:- Inner Surface of an arch.
4. Voussoirs:- These are wedge
shaped units.
5. Crown:- Highest part of extrados
B.C.Punmia
W.C.MacKay
Reference-

4. 6. Spandril:- Curved triangular
space form between extrados and
horizontal line.
7. Key:- Wedge-shaped unit fixed
at the crown of the arch.
8. Skew back:- It is inclined or
splayed surface on the abutment.
9. Springing points:- These
are the points from which the
curve of the arch spring.
10. Springing line:- It is an
imaginary line joining the
springing point of either ends.
Reference- B.C.Punmia
W.C.MacKay

5. 11. Abutment:-End point of
an Arch.
12. Springer:- It is the first
voussoir at springing level.
13. Pier:-Intermediate support
of an archade.
14. Arcade:- It is a row of
arches in continuation.
15. Haunch:-Lower half of the
arch between the crown and
skew back.
Reference- B.C.Punmia
W.C.MacKay

6. 16. Ring:-It is the circular course
forming an arch.
17. Impost:- It is the projecting
course at upper part of pier or
abutment to stress the springing
line.
18. Bed Joint:-Joints between the
Voussoirs which radiate from
centre.
19. Centre or Stricking
Point:- This is geometrical
centre point from where the arc
forming the extrados, arc rings,
intrados.
20. Span:-Clear horizontal distance
between the supports.
Reference- B.C.Punmia
W.C.MacKay

7. Arches are classified according to:-
1. Shape
2. Number of Centers
3. Workmanship and Material Used
Reference- B.C.Punmia
Google.com

8. Classification According to Shape
Flat Arch Segmental Arch
Semi-circular Arch
Pointed Arch
Florentine Arch
Stilted Arch
Horse Shoe Arch
Venetian Arch
Relieving Arch
Semi-Elliptical Arch
Reference- B.C.Punmia
Google.com

9. Flat Arch
 Forms an equilateral triangle with intrados as base( at an angle of 60°)
 Used only for light loads
 Weakest Arch
Reference- B.C.Punmia
Google.com

10. Segmental Arch
 Center of Arch lies below springing line.
 Thrust transferred to the abutment is in inclined direction.
 Most Common type of Arch.
Reference- B.C.Punmia
Google.com

11. Semi-circular Arch
 Center Lie on Springing line
 Shape of the arch is Semi-circular
 Thrust transferred to the abutment is perfectly in vertical direction
Reference- B.C.Punmia
Google.com

12. Horse Shoe Arch
 The arch has the shape of a horse shoe.
 Incorporating more than a semi circle.
 Mainly use for Architectural consideration.
Reference- B.C.Punmia
Google.com

13. Pointed Arch
 Also known as Gothic Arch.
 It consist two arc of the circle meeting at apex.
 Triangle form may be equilateral or isosceles(also known as Lancet
Arch).
Reference- B.C.Punmia
Google.com

14. Venetian Arch
 This is another form of Pointed Arch.
 Has deeper depth at crown than springings.
 It Has four centers located on springing line.
Reference- B.C.Punmia
Google.com

15. Florentine Arch
 This is similar to Venetian Arch.
 Its intrados is a semicircle.
 It has three centers located on springing line.
Reference- B.C.Punmia
Google.com

16. Relieving Arch
 The ends of Arch carried sufficiently into abutment.
 Its lintel can be replaced without effecting the Arch.
 The Arch is constructed on either flat arch or wooden lintel.
Reference- B.C.Punmia
Google.com

17. Stilted Arch
 An arch whose curve begins above the impost line.
 It consists a semi circular arch with two vertical portions at springings.
 The centre of the arch lies on the horizontal line.
Reference- B.C.Punmia
Google.com

18. Semi-Elliptical Arch
 It has shape of semi-ellipse.
 It has either three centre or five centre.
 Also called a basket-handle arch.
Reference- B.C.Punmia
Google.com

19. Classification According to Number Of
Centers
One-Centered Arch
Two-Centered Arch
Three-Centered Arch
Four-Centered Arch
Five-Centered Arch
Reference- B.C.Punmia
Google.com

20. One-Centered Arch
 It has only one center.
 Segmental Arches, Semicircular Arches, Flat Arches, Horse Shoe
Arches and Stilted Arches come under this Category.
 Sometimes full circular arch (Bulleye Arch ) provided for circular
windows.
Reference- B.C.Punmia
Google.com

21. Two-Centered Arch
 It has two centers.
 Pointed Arches comes under this category.
 Semi-elliptical arch and Florentine arch also comes under this category.
Reference- B.C.Punmia
Google.com

22. Three-Centered Arch
 It has three centers.
 Elliptical Arches comes under this category.
 Equilateral Arches also comes under this category.
Reference- B.C.Punmia
Google.com

23. Four-Centered Arch
 It has four centers.
 Venetian arch comes under this category.
 Another example is Tudor arch.
B.C.Punmia
Google.com
Reference-

24. Five-Centered Arch
 It has five centers
 Fives centers help in getting a good semi- elliptical shape
Reference- B.C.Punmia
Google.com

25. Classification Based On Material And
Workmanship
Stone Arch Brick Arch
Concrete Arch Reference- B.C.Punmia
Google.com

26. Stone Arch
1. Rubble Arches
 Weak and use for comparatively inferior
work.
 Made by stones which are dressed, roughly
shaped and sized as voussoirs
 Mortar is used for binding stones
2. Ashlars Arches
 Made by stones which are fully dressed and
in proper shape of voussoir.
 Lime or cement mortar is use as binding
material.
 Use for making Flat arches
Reference- B.C.Punmia
Google.com

27. Brick Arches
1. Rough Arch
 Made with ordinary bricks
 Joints are wedge-shaped with
greater thickness at extrados and
smaller thickness at intrados.
 Not used for exposed brick work.
2. Axed or Rough-cut Arch
 Made with wedge shaped bricks
 Joints are of uniform thickness.
 Not so attractive due to wedge
shaped bricks which are not finely
dressed.
Reference- B.C.Punmia
Google.com

28. 3. Gauged Arch
 Made with bricks which are prepared to
exact size and shape of voussoir.
 Joints are fine , thin and truly radial.
 Lime putty is use as a binding material.
4. Purpose made brick Arch
 Made with special bricks which are
manufactured in exact shape and size of
voussoirs.
 This is very fine workmanship.
 Lime putty is used as a binding material.
Reference- B.C.Punmia
Google.com

29. Concrete Arches
1. Concrete block-unit Arch
 Made with pre casted concrete
blocks.(moulds in shape of voussoirs)
 Good appearance and size of arch
achieved due to perfections.
 Cement mortar is used as a binding
material and joints are thin.
2. Monolithic Arch
 Made with cast-in- situ concrete, either
plain or reinforced.
 Suitable for large span.
 The thickness is 15cm for arches upto
3m span.
Reference- B.C.Punmia
Google.com