Technical Terms in Arches

 

Technical Terms in Arches

The definitions of technical terms used in connection with the archwork (i.e Arches) are as follows.

 

1) Intradose :

• This is the inner curve of arch.
  

  

  
  

2) Soffit :

• This is the inner surface of the arch.  
  

  

  
  

3) Extrados or Back :

• This is the external curve of an arch as shown in above image. 

4) Voussoirs :

• These are the wedge-shaped units forming the courses of an arch.
  

  

  
  

5) Crown :

• This is the highest point of the extrados.
  

  

  
  

6) Key :

• This is the wedge-shaped unit at the crown of an arch.
  

  

   
  

   

  
  

7) Arcade :

• This is a row of arches supporting a wall above & being supported by the piers.

8) Abutment :

• This is the end supports of an arcade.
  

  

  
  

9) Piers :

•  These are the intermediate supports of an arcade as shown in above image.

10) Springing Point :

• These are the points from which the curve of an arch springs.
  

  

  
  

11 ) Springing Line :

• This is the imaginary horizontal line joining the two springing points.
  

  

  
  

12) Skewback :

• This is the inclined or splayed surface on the abutment.
  

  

  
  

13) Springer :

• This is the first voussoir at springing level on either side of an arch & it is immediately adjacent to the skewback.
  

  

  
  

14) Span :

• This is the clear horizontal distance between the supports.
  

  

  
  

15) Rise :

• This is the clear vertical distance between the highest point on the intrados & the springing line.
  

  

  
  

16) Centre :

• This is the geometrical centre of the curve of an arch.
  

  

  
  

17) Ring :

• This is the circular course forming an arch. 

18) Depth or Height :

• This is the perpendicular distance between the intrados & extrados.

19) Spandrel :

• This is the irregular triangular space formed between the intrados & extrados.

  

  
  

20) Haunch :

• This is the lower half portion of the arch between the crown & the skewback.

  

  
  

21) Thickness or Breadth of Soffit :

• The horizontal distance measured perpendicular to the front & back faces of an arch is known as the thickness or breadth of soffit.

22) Impost :

The projecting course at the upper part of a pier or an abutment to stress the springing line is called the impost.

 

 

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