The ARCHES AND THEIR DECORATION
The square plan is the basis for the cross vault. Pure form of this arch, of four equal strikings with two mutually perpendicular axes, dictates a square shape plan. On the contrary, the barrel vault on a square plan produces a bad impression because of the contradiction between its one longitudinal axis and two axes of the plan. As bad and groin PA rectangular plan; when horizontal Stripping the crowns are in this case different shapes, with elliptic curve on the long side of the plan. Cross set on a rectangular plan loses its spatial integrity.
the halls of buildings like the Renaissance and later. A form was created for open spaces, and he willingly used by the best architects for recessed balconies (loggia dei Lanzi in Florence), exterior arcades (Educational house of Brunellesco). Dominating the lush surfaces of the baths and basilicas of Rome, groin gave way to the sailing arch in architecture of Byzantium and regained a dominant role in the architecture of Western feudalism XI—XIV centuries. Renaissance have found his true place in the exterior architecture of open facilities.
In the inner halls of Roman basilicas and baths, diagonal ribs of the cross vault are interfaced with the capitals of the columns (although there is the insert piece of the entablature), but the columns are not set and the charge after its construction . Pressure curve of the arch takes place in the thickness of the massive walls is much higher sham support — capitals of the colony. Knew that the builders of the Basilica, creating the perception of special thrust buttresses over the roof and setting the columns of expensive marble after the erection of the building, its finish .
In the visual perception of pillars carry the arch, and thus, met the requirements of tectonics, but in reality, the columns do not perform functions of a support arch.
Roman engineering skill was at the service of architecture, cannot be switched to the highest stage of approach to the synthesis of technology . Renaissance, using groin in external loggias and open arcades, correctly used basic, fundamental architectural properties. In the absence of walls diagonal ribs of the arch are guided by corner columns, which are their only support. Not making fake extra columns and buttresses masking of perceiving the thrust, the architects of the Renaissance were openly used the open metal connection.
Thus, we have two composite systems: the antique system of groin vaults in the Symphony hall of the Thermae, which gives aesthetic impression of floating light coverage, not dependent on the walls, but structurally, false, true, and complete system architecture of the Renaissance.
The first of these two systems, antique, Sedlmayr called the system of the canopy. You can accept this name, but you must specify that the coating of the open structures in the form of a rotunda, canopy (canopy), arcade, etc. where there is no walls and decorative columns, and there are only really loaded columns — such coverage must name the real canopies. Vaulted cover, in which through a side of the columns only the impression of loose, non-loaded walls, should be called a false canopy.
All architectural styles can be traced to this method of spatial composition — this system of the canopy, but in other different variants and interpretations. The geometric shape and the design of the system the canopy can be very diverse. For its spatial construction can be used to form the cross arch sailing, sailing-closed, fan and dome.
1 As is the case in the Church of St. Sophia in Constantinople, created by Anfimov Trueskin.
depicts a possible variant in the form of a mirror set on the columns. Mirror the arch of the Renaissance style was used mainly in closed spaces, on the walls; examples of mirror set on the columns is very rare. In Fig. 164 shows a mirror set on the columns in the Munich picture gallery Shaq, in Fig. 176—mirrored ceiling of the old hall in Paris.
Fig. 3 gives the third form of the canopy, sailing-closed vaults. This form is extremely rare. As an example, it is called Gothic arch in the French chapel of St. The Spirit (St. Esprit) in Rue.
Fig. 4 depicts baldachino the sailing system of spherical vaults. Along with the system of cross vaults, it is the most valuable in terms of architecture. Ancient Rome had not used this system. Byzantium in the era of Justinian gave the finished baldahina system: side galleries of St. Sophia in Constantinople form a Suite of freely floating spherical canopies on the pillars. In the Renaissance there have been limited applications of the sailing set, in the Pazzi chapel, in the portal of the Palace of the Uffizi in Florence (arch. Vasari), in the Palazzo Doria in Genoa (1564), in La Transcom Palace in Rome (1588), and others — but completed architectural canopy systems of this era we have left. In the later era especially interesting system of the canopy of sail vaults in two buildings of the French art of the XVIII—XIX centuries in the Church of Madlen in Paris, built by Vignon (1762— 1828), baldahina the system consists of three sail of the arches, resting on attached columns ; in the Paris Pantheon, built by Suffla (1709— 1780), four separate sailing canopy of cruciform plan resting on free-standing columns .
Fig. 5 depicts the canopy of the fan vaults. Amazing lightness and courage, the examples of such canopies is known in England of XIV —XV centuries. The best of them — in the chapel of Henry VII.
Fig. 6 gives the scheme of the violla Le Duke with conical funnels.
These examples demonstrate the variety of compositional and structural solutions of the canopy. In the following chapters we will return to this issue.
Now, after we noted the overall architectural and compositional features of the cross vault, the main form, place it in the General composition of construction and interpretation in different times — we turn to a detailed study of possible geometric shapes.
II. THE SHAPE OF THE CROSS VAULT
Basic, strictly geometrical form of the Roman groin vaults has undergone significant changes in the process of technical and decorative (style) development. Some changes have affected the main guide curves arch as strikings, and the diagonal ribs and the shape of the surface of the strikings themselves.
The Byzantine masters add a diagonal curve and simplify the shape of her curve. Low elliptic curve instead of a diagonal edge draws the same radius from the low center (Fig. 183). Arch height is obtained is greater than with a simple cylindrical strikings (equal to half the base side plus some value of h, less paludicola). Seligi strikings are raised (sparsely), the surface of the cylindrical becomes spheroidal. The cross section of the spheroidal arch spandrel horizontal planes gives chetyrehkantnye shaped.
From this example it is clear, as the change form of the curves of the arch entails changing the shape of the spandrel due to the close connection between these elements. In addition to curves and striking, is changed and the angle of the diagonal ribs at the support he is 90°, the upward edge to selige it increases and vanishes at the top (180°); with a raised curve flattening angle to Selye goes faster. This commutation angle was used by Renaissance architects for decorative purposes — to get in selige smooth surface (ceiling) of a large size.