Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 The characteristics of star vaults in Seljuk Anatolia A.T. Yavuz Middle East Technical University, Faculty of Architecture, Master Program in Conservation, Ankara, Turkey ABSTRACT Both in the medieval gothic world as well as in the Near East there are vaults which display various star shapes in their plans. Several of these plans are very similar, however, the sections, the geometric form they are part of, the existence or the non-existence of ribs produce a large variety in different parts of the medieval world. The intention of this paper is to introduce the characteristics of the Seljuk Period star vaults in Turkey and compare them with other star vaults in other parts of the world. INTRODUCTION Architectural historians are well aware that many medieval and later monuments have vaults which include a star form in their plans and they are called "star-vaults". This paper will limit itself only with those vaults where the stars are not mere decoration but the lines that contribute to the starform are integral parts of the vaults, that is the vault could not be defined or just exist without their presence. In such vaults the lines of the star may coincide with the ribs, they may correspond to the groins where various facets meet, they may also form the groin where two different vaults with different profiles or different volumetric forms meet. In some cases they may be further emphasized by coloring the lines or by the contrast between the cut stone ribs and the plastered rubble stone webs between them. Anatolian Seljuk Star Vaults Anatolian star vaults do not altogether form a different type of vault from the types already known. They are all a derivative of the cross vault which constitutes 20% of all types of vaults and domes in Anatolian Seljuk architecture. They display Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 166 Structural Repair and Maintenance of Historical Buildings such characteristics of the cross vault as the profile at the four sides, the groin lines where the two barrel vaults meet, the typical section of the cross vault which is a straight horizontal line because the intersecting barrel vaults are parts of cylinders. The form of the star is the result of facets folding in and out and which start at the corners. There are altogether twenty-two examples that have survived to our day from the Xllth and the XHIth Centuries. Nine of them are intact or with little damage, six of them are so badly damaged that they could not be measured, and seven of them do not cover a space or a bay by themselves but are part of a larger combined or composite superstructure. All except the one in the Han near Igdir, Kars [R.H.Unal (3)] have been measured and studied in detail, which are fifteen altogether [A.T.Yavuz (1)]. These vaults have been studied between the years 1965- 1982. Their measured surveys in 1/20 scale include a plan, a plan of the coursing of the material, at least one section, and the geometric set-up of the vault [A.T.Yavuz (1,2)]. Anatolian Seljuk star vaults are of the faceted kind and they can be a classified according to the number of the facets which are created by the lines that may be interpreted as the multiplication of the groin at each arm of the vault. A secondary criteria for the classification is the geometric form of the "center" of the vault, to the corners of which the lines join. Some corners of the centers accommodate two lines from two arms whereas some others have only one line meeting the corner. This depends on the relation of the corner to the springing point of the lines at each arm. Usually the corners on the midline of the sides accommodate two lines. The differentiation from the cross vault starts with 2 lines, instead of the single groin line. The extant Anatolian Seljuk star vaults vary between those with 2 lines-3 facets to these with 7 lines-8 facets, but the majority of them have 3 lines-4 facets. Generally the lines between the facets are odd in number rather than even. This contributes to the continued existence of the groin line emphasizing their basic relationship with the cross vault as well as forming a symmetry axis on each arm of the vault. Another shared feature is the coursing of the material both in stone and brick. The courses start perpendicular to the sides, as is common in cross vaults but they fold at the facets following the outline of the center, parallel to it. This type of coursing creates concentric replicas of the geometric form of the center, like ripples in water, emphasizing its form. Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 Structural Repair and Maintenance of Historical Buildings 167 Examples The only extant star vault with 2 lines-3 facets is located on the east end of the north riwaq in the Keykavus Daru§§ifasi (Hospital) (AD 1217-20) in Sivas. The central and the north parts of the vault have crollen therefore the form of the center cannot be determined even though the 2 lines and 3 facets of the arms are clearly visible. The number of lines from four arms require four corners to join. A square center with its corners pointing to the midpoints of the sides seems to be the right geometric solution and this is the form of the centers at similar star vaults in the Ye§il Cami and Medrese in Bursa, from the Early Ottoman Period (Photo 1). In vaults with 2 lines-3 facets, because there are even number of lines the groin lines of the vault have disappeared instead the facets which determine the four arms of the star are more emphasized. The majority of the star vaults have 3 lines-4 facets. There are seven intact or partially crollen, four badly ruined or completely crollen vaults of this type covering individual spaces or bays. There are seven others, used completely or partially, as parts of other combined or composite super- structures, adding up to eighteen altogether (the latter group will not be part of this paper except for comparison). These vaults have similar features but no two are exactly alike. All of them, except one, have octagonal centers. The octagon is so located that its corners are on the bisectors of the sides and the diagonals of the vault. The three lines that start from each corner of the vault join the corners of the octagon nearest to them. Neither size of the octagonal center, its geometric relationship with the vault, nor its treatment as a straight, recessed or articulated panel effect this basic relationship. The star vault with the unusual center covers the fifth bay from the West, in the south riwaq in Sivas Keykavus Daru§§ifasi (N.4.20m/S.4.24m/E.4.32mAV.4.26m) (Figure 1,2). The brick vault has a two near-centered-recessed shouldered profile. There are four equilateral triangles, one on each side, starting with its base on it. The sides of the triangles extend towards the center forming a four-armed star, each arm of which is equal to the generating triangle. The central one of the 3 lines meets the corner where the tips of the two reverse triangles meet whereas the outer two lines join the inner corners of the star. It is not possible to detect if the generation of triangles and stars continues further or if there is only a plain square at the center because the central part of the vault is partially crollen, partially plastered. But it is clearly visible that the coursing of the bricks follow the Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 168 Structural Repair and Maintenance of Historical Buildings outline of the star and the triangles, whereas it is parallel to the side of the vault inside the exterior triangles. Another brick example is over the entrance eyvan in Sivas Gok Medrese (A.D.I 271) (Photo 2). The star covers the square area at the center of the rectangular space (N.6.38m/S.6.38m/E. 3.89m/W.3.80m) and the intersecting barrel vault extends further in the north-south direction to cover the areas at the ends. The basic cross vault has a two centered - pointed profile. The octagonal center which is equal to half of the width in size is treated as two concentric rings. The outer one is 0.96m in diameter and is recessed 0.06m whereas the inner one, 0.96m in diameter, is in the form of a lobed projection hanging from the center. The vault is completely plastered and whitewashed now but there is the possibility of the use of glazed bricks or colored tiles, especially at the hanging center. The 3 lines-4 facets star vault over the second bay from the East of the fourth horizontal aisle from the South in Divrigi Ulu Camisi (Great Mosque) (AD 1228-29) also has a rectangular plan but this time the plan is reduced to a square by a 0.96m wide arch on each end of the long sides (N.4.53m/S. 4.50m/E.4.66m/W.4.62m). The vault has a depressed two-centered- pointed profile.