Arches

1.1: Introduction

           Always an Architects wish to add beauty and elegance to buildings. Also the people like the way in which it looks as attractive and beautiful with respect to the surroundings. It becomes customary to add arches for the openings not only outside the building but also for the door and openings.

           An arch is the mechanical arrangement of wedge-shaped blocks of bricks or stones, mutually supporting each other and supported at the end by piers or abutments.

1.2: Function of arches

1)To carry the weight of the structure above the opening.

2)To increase the aesthetic beauty of the structure.

1.3: Some terminologies

1)Abutment of pier

           It is the part of the wall or pier on which the arch rests.

2)Arch ring

          This is the course of stones or bricks having a curve similar to that of the arch.

3)Intrados

         The curve which bounds the lower edge of the arch and The distinction between soffit and intrados is that the intrados is a line, while the soffit is a surface.

4)Crown

          The apex of the Arch’s extrados. In symmetrical arches, the crown is at the mid-span.

5)Rise 

         The maximum height of the arch can be said as soffit above the level of its spring line.

6)Soffit

          The soffit may be defined as the surface of an arch or vault at the intrados.

7)Span

            The horizontal clear dimension between abutments.

8)Spandrel

           The spandrel may be defined as the masonry contained in between a horizontal line drawn through the crown and a vertical line drawn through the uppermost point of the skewback.

9)Springing

         The point where the skewback intersects the intrados.

10)Springer

         The first voussoir from a skewback.

11)Sping Line

          A horizontal line that intersects the springing.

12)Voussoir

            One masonry unit of an arch.

13)Depth of arch

           It is the perpendicular distance between the intrados and extrados.

14)Haunch of the arch

          The portion of the arch which is situated centrally between the key and skew backs.

15)Skewback

         The skewback may be defined as the surface of the abutment on which the arch rests.

1.4: Load on arch

          When the ratio of fill above the crown to the span of the arch less than 1, the full weight of fill will be borne by arch. This gives an idea that when the arch is used at a limited level the weight of the brick masonry above the lintel and the floor loads is carried by the arch.

1.5: Rise of the arch

        The rise of the arch generally is between 1/3 to 1/4 of the span for the economy ; the smaller value being applicable to a relatively larger span and a large value for relatively smaller spans.

1.6: Types of Arch

A)Based on construction material

     1)Brick arches

     2)Stone arches

     3)Concrete arches

B)Commonly adopted in construction

      1)Flat arch

      2)Semi-Circular arch

      3)Segmental arch

      4)Relieving arch

      5)Dutch or french arch

C)Based on shape

       1)Circular

       2)Semi-circular

       3)Flat

       4)Triangular etc

Leave a Reply

Your email address will not be published. Required fields are marked *