Islamic Vaulting

In Islamic buildings, vaulting follows two distinct architectural styles: Whilst Umayyad architecture continues Syrian traditions of the 6th and 7th century, Eastern Islamic architecture was mainly influenced by Sasanian styles and forms.

Umayyad diaphragm arches and barrel vaults
In their vaulting structures, Umayyad period buildings show a mixture of ancient Roman and Persian architectural traditions. Diaphragm arches with lintelled ceilings made of wood or stone beams, or, alternatively, with barrel vaults, were known in the Levant since the classical and Nabatean period. They were mainly used to cover houses and cisterns. The architectural form of covering diaphragm arches with barrel vaults, however, was likely newly introduced from Iranian architecture, as similar vaulting was not known in Bilad al-Sham before the arrival of the Umayyads. However, this form was well known in Iran from early Parthian times, as exemplified in the Parthian buildings of Aššur. The earliest known example for barrel vaults resting on diaphragm arches from Umayyad architecture is known from Qasr Harane in Syria. During the early period, the diaphragm arches are built from coarsely cut limestone slabs, without using supporting falsework, which were connected by gypsum mortar. Later-period vaults were erected using pre-formed lateral ribs modelled from gypsum, which served as a temporal formwork to guide and center the vault. These ribs, which were left in the structure afterwards, do not carry any load. The ribs were cast in advance on strips of cloth, the impression of which can still be seen in the ribs today. Similar structures are known from Sasanian architecture, for example from the palace of Firuzabad. Umayyad-period vaults of this type were found in Amman Citadel and in Qasr Amra.

Islamic Spain
The double-arched system of arcades of the Mosque–Cathedral of Córdoba is generally considered to be derived from Roman aqueducts like the nearby aqueduct of Los Milagros. Columns are connected by horseshoe arches, and support pillars of brickwork, which are in turn interconnected by semicircular arches supporting the flat timberwork ceiling.

In later-period additions to the Mosque of Córdoba, the basic architectural design was changed: Horseshoe arches were now used for the upper row of arcades, which is now supported by five-pass arches. In sections which now supported domes, additional supporting structures were needed to bear the thrust of the cupolas. The architects solved this problem by the construction of intersecting three- or five-pass arches. The three domes spanning the vaults above the mihrab wall are constructed as ribbed vaults. Rather than meeting in the center of the dome, the ribs intersect one another off-center, forming an eight-pointed star in the center which is superseded by a pendentive dome.

The ribbed vaults of the mosque-cathedral of Córdoba served as models for later mosque buildings in the Islamic West of al-Andaluz and the Maghreb. At around 1000 AD, the Mezquita de Bab al Mardum (today: Mosque of Cristo de la Luz) in Toledo was constructed with a similar, eight-ribbed dome. Similar domes are also seen in the mosque building of the Aljafería of Zaragoza. The architectural form of the ribbed dome was further developed in the Maghreb: The central dome of the Great Mosque of Tlemcen, a masterpiece of the Almoravids built in 1082, has twelve slender ribs, the shell between the ribs is filled with filigree stucco work.

Islamic Iran(Persia)
Because of its long history of building and re-building, spanning the time from the Abbasids to the Qajar dynasty, and its excellent state of conservation, the Jameh Mosque of Isfahan provides an overview over the experiments Islamic architects conducted with complicated vaulting structures.

The system of squinches, which is a construction filling in the upper angles of a square room so as to form a base to receive an octagonal or spherical dome, was already known in Sasanian architecture. The spherical triangles of the squinches were split up into further subdivisions or systems of niches, resulting in a complex interplay of supporting structures forming an ornamental spatial pattern which hides the weight of the structure.

The "non-radial rib vault", an architectural form of ribbed vaults with a superimposed spherical dome, is the characteristic architectural vault form of the Islamic East. From its beginnings in the Jameh Mosque of Isfahan, this form of vault was used in a sequence of important buildings up to the period of Safavid architecture. Its main characteristics are:

Four intersecting ribs, at times redoubled and intersected to form an eight-pointed star;
the omission of a transition zone between the vault and the supporting structure;
a central dome or roof lantern on top of the ribbed vault.
While intersecting pairs of ribs from the main decorative feature of Seljuk architecture, the ribs were hidden behind additional architectural elements in later periods, as exemplified in the dome of the Tomb of Ahmed Sanjar in Merv, until they finally disappeared completely behind the double shell of a stucco dome, as seen in the dome of Ālī Qāpū in Isfahan.

Domes
Based on the model of pre-existing Byzantine domes, the Ottoman Architecture developed a specific form of monumental, representative building: Wide central domes with huge diameters were erected on top of a centre-plan building. Despite their enormous weight, the domes appear virtually weightless. Some of the most elaborate domed buildings have been constructed by the Ottoman architect Mimar Sinan.

When the Ottomans had conquered Constantinople, they found a variety of Byzantine Christian churches, the largest and most prominent amongst them was the Hagia Sophia. The brickwork-and-mortar ribs and the spherical shell of the central dome of the Hagia Sophia were built simultaneously, as a self-supporting structure without any wooden centring. In the early Byzantine church of Hagia Irene, the ribs of the dome vault are fully integrated into the shell, similar to Western Roman domes, and thus are not visible from within the building. In the dome of the Hagia Sophia, the ribs and shell of the dome unite in a central medallion at the apex of the dome, the upper ends of the ribs being integrated into the shell: Shell and ribs form one single structural entity. In later Byzantine buildings, like the Kalenderhane Mosque, the Eski Imaret Mosque (formerly the Monastery of Christ Pantepoptes) or the Pantokrator Monastery (today: Zeyrek Mosque), the central medallion of the apex and the ribs of the dome became separate structural elements: The ribs are more pronounced and connect to the central medallion, which also stands out more pronouncedly, so that the entire construction gives the impression as if ribs and medallion are separate from, and underpin, the proper shell of the dome.

Mimar Sinan solved the structural issues of the Hagia Sophia dome by constructing a system of centrally symmetric pillars with flanking semi-domes, as exemplified by the design of the Süleymaniye Mosque (four pillars with two flanking shield walls and two semi-domes, 1550–1557), the Rüstem Pasha Mosque (eight pillars with four diagonal semi-domes, 1561–1563), and the Selimiye Mosque in Edirne (eight pillars with four diagonal semi-domes, 1567/8–1574/5). In the history of architecture, the structure of the Selimiye Mosque has no precedent. All elements of the building subordinate to its great dome.

Source From Wikipedia