One of the things our early ancestors wanted to do was to build structures for housing, walls for protection and special buildings for religion. Building a wall from rough stone is time consuming but possible as we have seen in the last post. If you have a lot of large flat stones and you are building rather low buildings, you don't need to make an arch, you can just put a flat stone on top of stone pillars and you have an opening. The problem with stone pillars topped with a flat lintel is that it cannot bear much weight. As seen in the figure to the right, when a large force is applied downward, the lintel beam is alternately compressed on the upper side and pulled outwards on the bottom. Rock is very incompressible but often has small imperfections that allow cracking on the bottom, leading to failure. This same principle is the reason we can scratch glass and break it along the resulting fault. If you are using brick, the problem becomes insurmountable, you must have an arch or a stone lintel to make an opening in the wall (a door or window). Everyone has seen the karate trick of breaking a brick held by two blocks of wood. The only problem with arched openings is that the arch converts downward force into sideways forces and must be buttressed on both sides.
Ġgantija is a Neolithic, megalithic temple complex on the Mediterranean island of Gozo. The Ġgantija temples are the earliest of a series of megalithic temples in Malta. The Ġgantija temples are older than the pyramids of Egypt. Their makers erected the two Ġgantija temples during the Neolithic Age (3600-2500 BC), which makes these temples more than 5500 years old and the world's second oldest manmade religious structures, after Göbekli Tepe. Here we see the lintel and column method of construction.
One of the oldest arches in the world, at Edublalmahr temple in ancient Ur, which is dedicated to the moon. On the site there is a Summerian temple called the Ziggurat dating back to 2100 BC, the remains of Abraham's house, 7000-year-old graves, and many other things that have not been excavated yet. Here we have a classic arch executed in mud brick.
The three sun-dried mud–brick arches of Tel Dan spanning the gatehouse passageway are the world’s oldest known complete and free-standing monumental ‘true’ arches made of this material. This gatehouse is dated to the mid-18th century BC, and stands today more than 7 m high. The city gate was excavated during the 1978–1985 seasons, revealing a vast gatehouse in a remarkable state of preservation. All its three arches were soundly constructed in three concentric radial courses of mud brick.
The architectural technology of Mesopotamia is most often illustrated by the massive mud-brick ziggurat. While the ziggurat is a visually striking structure, it in no way demonstrates the varied methods of construction available to the ancient builder. One of these methods was pitched brick vaulting, a Mesopotamian method for vault construction subsequently used in the West. The pitched brick vault (see above) is initially supported by a single bearing wall at the back. The courses of the vault are then laid at right angles to the courses of the wall. Each vault course is tipped somewhat off the vertical so that the initial courses lean against the back wall, and subsequent courses rest against the first. This vertical orientation of the courses, in addition to the tip or pitch, distinguishes the pitched vault from radial construction where the vault merges into the wall surface. A pitched vault is always identifiable by a change in the orientation of the brick courses in the interior of the vault Unless obscured by the plaster, the springing point of the vault is marked by the juncture of the horizontal wall courses and the vertical vault rings. The pitched brick wall is preferable to a radial vault in some circumstances because it is extremely stable and because it may be erected without the elaborate timber centering needed to support a radial vault during its construction. In earthquake-prone and timber-poor Mesopotamia these qualities would have been appreciated. The pitched brick vault has long been considered a characteristic of Parthian architecture in Mesopotamia. This technique was used first by the Greeks and then by the Romans for underground aqueducts. It was also used in graves in the Nile Delta by Egyptians.
Haft Tepe (“seven hills” – in fact twelve) in modern Khuzestan (ancient Elam) is probably identical to an ancient town named Tikni. The site is halfway Susa and Choga Zanbil and dates back to the fifteenth century BCE. Three parts have been identified: a temple with the royal tomb, the palace area, and the artisans' quarter. Here we see an example of a pitched brick barrow used for a royal funeral chamber.
Ashkelon was a thriving Middle Bronze Age (2000–1550 BC) city of more than 150 acres, with commanding ramparts including the oldest arched city gate in the world, eight feet wide, and even as a ruin still standing two stories high. The thickness of the walls was so great that the mudbrick Bronze Age gate had a stone-lined tunnel-like barrel vault, coated with white plaster, to support the superstructure: it is the oldest such vault ever found. Notice that the arch is not circular but instead parabolic. This design is much stronger than a circular arch and we will return to the subject in the construction of pointed Gothic arches and barrel vaulted ceilings.
Tell al-Rimah (in modern Ninawa Governorate, Iraq roughly 50 miles west of Mosul) was the Ancient Near East city of Karana or Qattara in the Sinjar region west of Nineveh. While it appears that the site was occupied in the 3rd millennium, it reached its greatest size and prominence during the 2nd millennium and in the Neo-Assyrian period. The second millennium activity was primarily during the Old Babylonian and Mitanni times. Tell al-Rimah also is known for having a 3rd millennium example of mud brick vaulting.
A corbel arch is constructed by offsetting successive courses of stone (or brick) at the springline of the walls so that they project towards the archway's center from each supporting side, until the courses meet at the apex of the archway (often, the last gap is bridged with a flat stone). For a corbeled vault covering the technique is extended in three dimensions along the lengths of two opposing walls. Although an improvement in load-bearing efficiency over the post and lintel design, corbeled arches are not entirely self-supporting structures, and the corbeled arch is sometimes termed a “false arch” for this reason. Corbel arches and vaults require significantly thickened walls and an abutment of other stone or fill to counteract the effects of gravity, which otherwise would tend to collapse each side of the archway inwards.
Newgrange is the finest of some 26 ancient tribal burial chambers in the Boyne River Valley north of Dublin. A great round tomb with fine rock carvings, Newgrange is about 5,000 years old – making it centuries older than the Great Pyramids of Egypt and a thousand years older than Stonehenge. The complex of Newgrange was originally built between c. 3200 and 3100 BC. According to carbon-14 dates, it is about five hundred years older than the current form of Stonehenge, and the Great Pyramid of Giza in Egypt, as well as predating the Mycenaean culture of ancient Greece. Notice how the corbel technique has been extended to make a passage.
The Treasury of Atreus or Tomb of Agamemnon is an impressive “tholos” tomb (one of about 6 in the area) on the Panagitsa Hill at Mycenae, Greece, constructed during the Bronze Age around 1250 BC. The lintel stone above the doorway weighs 120 tons, the largest in the world. It is formed of a semi-subterranean room of circular plan, with a corbel arch covering that is ogival (pointed like a Gothic arch) in section. With an interior height of 13.5m and a diameter of 14.5m, it was the tallest and widest dome in the world for over a thousand years until construction of the Temple of Hermes in Baiae and the Pantheon in Rome. Great care was taken in the positioning of the enormous stones, to guarantee the vault's stability over time in bearing the force of compression from its own weight.
The lintel stone above the doorway weighs 120 tons, the largest in the world. While the lintel seems unnecessary it provides additional stability for the doorway. The corbel arch removes weight from the vulnerable center of the lintel and distributes it onto the much stronger sides.
In the second millennium BC Mycenae was one of the major centers of Greek civilization, a military stronghold which dominated much of southern Greece. The period of Greek history from about 1600 BC to about 1100 BC is called Mycenaean in reference to Mycenae. The engineers of Mycenae were very skilled in corbelling techniques and they were able to build long vaulted passages and domes which have not collapsed and this is particularly remarkable when considering that Greece is a country subject to severe earthquakes. The corbelled passage above leads to an underground water source.
The Arkadiko Corbelled Bridge is a Mycenaean corbel bridge near the modern road from Tiryns to Epidauros on the Peloponnese, Greece. Dating to the Greek Bronze Age 1300–1190 BC, it is one of the oldest arch bridges still in existence and use. The structure is 22 meters (72 ft) long, 5.60 meters (18.4 ft) wide at the base and 4 meters (13 ft) high. The width of the roadway atop is about 2.50 meters (8 ft 2 in).
The Eleutherna Bridge is an ancient Greek corbel arch bridge near the Cretan town of Eleutherna, Greece. The opening is cut from the unmortared limestone blocks in the shape of an isosceles triangle, the height of which is 1.84 m. The overall length of the bridge measures 9.35 m. Its width varies from 5.1 to 5.2 m, with the structure converging slightly towards its center point above the arch (5.05 m width there). The height is between 4 and 4.2 m. The date of construction is uncertain, probably 3-4th century BC.
The Romans did not invent the arch. Indeed, arches have been used since prehistoric times. The ancient Egyptians, Babylonians, and Greeks all used it as I have shown above. The purpose of the arch in these cultures, however, was limited to supporting small structures, such as storerooms, and people often used columns to support the roof. This design limited the size and scope of a building. As a result, builders could not construct extremely large palaces or government buildings. The arch became the Swiss army knife for Roman architects. One of the most visible Roman uses of arches was for aqueducts such as the one above, the Pont du Gard Aqueduct, in France, which was built shortly before the Christian era to allow the aqueduct of Nîmes (which is almost 50 km long) to cross the Gard river. The Roman architects and hydraulic engineers who designed this bridge, which stands almost 50 m high and is on three levels – the longest measuring 275 m – created a technical as well as an artistic masterpiece.
The Romans were the first to tinker with the arch realizing that a full semicircle was not always necessary as seen above. These were called segmental arches. The picture shows an insulae or apartment building in Ostia Antica. The insulae could be up to six or seven stories high, and despite height restrictions in the Imperial era, a few reached eight or nine stories.
Romans did not use large barrel vaults often, due to the need to create thick, buttressed walls, mostly without windows on each side to support the outward force of the vault. One example is seen at Bath in England where a 10.5 meter vault was created over the baths. The builders accomplished this with a system of brick ribs filled in between with hollow brick voussoirs to reduce the weight of the vault. Even so, the vault eventually collapsed.
One really large example of barrel vaulting in Rome is the Basillica Nova. Construction began on the northern side of the forum under the emperor Maxentius in 308, and was completed in 312 by Constantine I after his defeat of Maxentius. The building consisted of a central nave covered by three groin vaults suspended 39 meters above the floor on four large piers, ending in an apse at the western end containing a colossal statue of Constantine. The lateral forces of the groin vaults were held by flanking aisles measuring 23 by 17 metres (75 x 56 feet). The aisles were spanned by three semi-circular barrel vaults perpendicular to the nave, and narrow arcades ran parallel to the nave beneath the barrel vaults. The nave itself measured 25 metres by 80 metres (83 x 265 feet) creating a 4000 square meter floor (or about one acre). This was by far the largest building in the forum and the largest building anywhere when it was built. Basilicas served a variety of functions, including a combination of a court-house, council chamber and meeting hall. Under Constantine and his successors this type of building was chosen as the basis for the design of the larger places of Christian worship, presumably as the basilica form had fewer pagan associations than those of the designs of traditional Greco-Roman temples, and allowed large congregations. As a result of the building programs of the Christian Roman emperors the term basilica later became largely synonymous with a large church or cathedral.
The Augustinian Monastery of Sant Jaume de Frontanyà is located in center of the town of the same name, in the Catalan region of the Berguedà in Spain. This picture shows four important architectural elements. First the barrel vault leading to a four sided area which supports a circular tower. The Squinch was probably invented in Iran and exported to Europe allowing a square base to hold up a circular tower. The tiny windows are typical of heavy Romanesque architecture.
I am going to finish this post with a description of the method Romans preferred over a barrel vault to create large open spaces, the Groin Vault. As you can see in the above figure, the Groin Vault is simply two barrel vaults at right angles. The result is a very strong vault with almost all the forces pointed down and lots of open space at the bottom (as in for instance windows).
You can add them side by side to make a long apse that looks like a barrel vault but has wide open space on the sides for lots of windows, the hallmark of a Gothic cathedral. Finally, it is difficult to construct a groin vault with semicircular arches, it turns out to be easier and stronger to make pointed arches typical of Gothic Arches.
If you have done all of this correctly, you end up with an ethereal space like the central nave of Saint Denis Cathedral, shown above. You can now easily identify the ribbed groin vaults in the vaulted ceiling. Well, that's it for now, sorry for the length and all the terminology as always. Much more to come on Gothic Cathedrals.
Pictures of Ur: http://forum.skyscraperpage.com/showthread.php?t=179329
Haft Tepe: http://www.travelblog.org/Photos/1183045
Tell Dan: http://teldan.wordpress.com/
Tell al Rimah: http://www.zeably.com/Tell-el-Rimah
Parthian Brick Vaults: http://www.jtsa.edu/Documents/pagedocs/JANES/1982%2014/Kawami14.pdf
Bath Barrel Vault: http://www.arct.cam.ac.uk/Downloads/ichs/vol-2-1829-1844-lancaster.pdf
Basilica Nova: http://www.icomos.org/madrid2002/actas/267.pdf
Basilica Nova: http://repository.upenn.edu/dissertations/AAI3165666/