How did roman arch improve on the post-and-lintel system used by the greek?
The Etruscans are said
to have invented the simple arch, or barrel arch. The oldest
example of the vaulted arch has been found in the Greek city of
Pergamon (in western Turkey). The vaulted arch came into forms, the
groin arch where two to four barrel arches intersected and the rib
arch, where the intersecting barrels were not of the same
diameter.
The Romans were the
first to make extensive use of the (barrel) arch and the vault.
This came as part of what has been called the Roman architectural
revolution or concrete revolution. The Romans invented a form of
concrete which was as strong as modern concrete. The Romans started
making arches and vaults in concrete (although stone-made ones were
not abandoned). Concrete was modelled in arch or vault formwork.
This made the building of these structures quicker, gave it a
stronger material, made it possible to build bigger ones, and lead
their monumental use of a much grander scale.
The Romans were also
the first to build large and monumental domes. Again this was made
possible by the use of concrete. The best example of this is the
dome of the rotunda of the pantheon in Rome, which is still the
largest unreinforced concrete dome in the world. This was a temple
dedicated to all gods and is well preserved because it was
converted into a Christian church.
The Romans experimented
with the pedentive dome in the 2nd and 3rd centuries AD. It was
fully developed with the revolutionary dome of for the famous Hagia
Sophia church in Constantinople (which is now Istanbul) in the 6th
century. It is a masonry dome. Pedentives are triangular segments
of a sphere which fill the spaces between four arches placed in a
spare shape and form a continuous circular of elliptical base which
supports the dome.
Prior to the pedentive,
squinces were used to build octagonal or spherical domes on top of
square rooms. Squinces were fillings in the upper corners of a
square room. Masonry was used to fill the corers with a vice placed
diagonally. They could also be placed on top of four corbelled
arches placed to form a square, again, diagonally across the
corners of the rooms - corbel arch was similar to but not as good
as a "true" arch. This technique was invented by the Persians and
was used during the Sasanian Empire (the last of the four
pre-Islamic Persian empires, 224-651) to build large domes. The
pedentive was a more advanced structure and allowed for building
much larger domes