This document discusses arches and their elements. It defines key terms like intrados, extrados, voussoirs, crown, and springing line. It describes how arches transmit loads through compression between wedge-shaped units. Arches are classified by their shape (flat, segmental, semicircular), number of centers (one-centered, two-centered), and construction material (stone, brick, concrete). Common arch types include flat arches, segmental arches, semicircular arches, and pointed Gothic arches.

1. ARCHES

2. INTRODUCTION
 An arch is a structure constructed of wedge-
shaped units, jointed together with mortar &
spanning an opening to support the wall above it
with other super-imposed loads.
 Due to wedge-like form, the units support each
other, the load tends to make them compact &
enables them to transmit the pressure
downwards to their supports.

3. ELEMENTS OF SEGMENTAL
ARCH
 INTRADOS:- This is the inner curve of an arch.
 SOFFIT:- It is the inner surface of an arch.
Sometimes, intrados & soffit are used synonymously.
 EXTRADOS:- This is the outer curve of an arch.
 VOUSSOIRS:- These are wedge-shaped units of
masonry, forming an arch.
 CROWN:- it is the highest part of extrados.
 KEY:- it is the wedge-shaped unit fixed at crown of
the arch.
 SPANDRIL:- This is the triangular space formed
between the extrados & the horizontal line through
the crown.

4. ELEMENTS OF SEGMENTAL
ARCH
 ABUTMENT:- This is the end support of an
arch.
 PIER:- This is the intermediate support of an
arcade.
 ARCADE:- It is a row of arches in continuation.
 SKEW BACK:- This is the inclined surface on
the abutment, which is so prepared to receive an
arch.
 SPRINGING LINE:- It is an imaginary line
joining the springing points of either end.
 SPRINGER:- it is the first voussior at springing
level. It is immediately adjacent to the skewback.
 HAUNCH:- It is the lower half of the arch
between the crown and skew back.

5. ELEMENTS OF SEGMENTAL
ARCH

6. STABILITY OF AN ARCH
 An arch transmit the super-imposed load to the
side wall through friction between surfaces of
voussior and the cohesion of mortar.
 Every element of arch remains in compression.
 An arch may fail in the following types:-
a) Crushing of the masonry
b) Sliding of voussior
c) Rotation of joints about an edge.
d) Uneven settlement of abutment/pier.

7. CLASSIFICATION OF ARCH
 According to shape
i) Flat Arch
ii) Segmental Arch
iii)Semicircular Arch
iv)Horse shoe Arch
v) Pointed Arch (Gothic Arch)
vi)Venetian Arch

8. CLASSIFICATION OF ARCH
 Classification based on number of centers
i) One-Centered Arches
ii) Two-Centered Arches
iii)Three-Centered Arches
iv)Four-Centered Arches
v) Five-Centered Arches

9. CLASSIFICATION OF ARCH
 Classification based on material of construction
and workmanship
 Stone Arches
a) Rubble Arch
b) Ashlar Arch
 Brick Arches
a) Rough Arch
b) Axed or rough-cut Arch
c) Gauged Arch
d) Purpose made brick Arch
 Concrete Arches

10. FLAT ARCHES

11. SEGMENTAL ARCH

12. SEMI-CIRCULAR ARCH

13. HORSE SHOE ARCH

14. POINTED ARCH