Geometry, material, and construction technique of the belt of Turkish triangles: An innovative architectural and structural solution developed in Anatolia for transitional zone challenges

Between the 12th and 15th centuries, the belt of Turkish triangles, which was developed as an original solution in the transition from cubic space to the dome in Anatolia, found widespread application as a common transition element from the Seljuk Period to the Principalities and the Early Ottoman Periods. In addition to its structural features, the aesthetic values arising from the rich geometric combinations of the belt of Turkish triangles have played a significant role in its use as a transitional element. In historical buildings, where roofs or walls have been damaged for various reasons, the transitional zones between them often represent the most vulnerable areas, requiring careful intervention. Therefore, a detailed understanding and analysis of the original architectural and structural characteristics of cultural heritage buildings are of primary importance. Although the Turkish triangle belt has been examined primarily from a formal perspective in architectural history, studies that focus on material and construction techniques remain quite limited. In this context, the present study aims to provide a comprehensive analysis of the geometric/formal, material, and constructional characteristics of the transitional zones employing the belt of Turkish triangles in between the 12th and 15th centuries. Accordingly, the construction techniques of different geometric configurations have been modelled in three dimensions. The study is structured in three main stages. First, the geometric/formal features of the belt of Turkish triangles-particularly at surfaces and corners are examined using the data obtained from literature and field studies. The geometric scheme of the transitional zone is also analysed from various perspectives, including the relationship between the substructure and superstructure as well as facade characteristics. Second, the material and construction technique employed in the belt of Turkish triangles are investigated. Finally, the construction process of different types of the belt of Turkish triangles is modelled step by step and presented in detail. Transition zone with the belt of Turkish triangles, which is composed of variations of plane and triangular prisms, exhibits geometric differences particularly in the corner units. Although the use of stone material in the construction of plane triangles is rarely encountered, the belt of Turkish triangles is predominantly built using brick, often with thick mortar joints between the units. Before the construction of the transitional zone, a single or a few rows of bricks are laid slightly projecting from the wall surface where the wall ends, in order to level the base and define the starting line of the transition zone. Once the height of the transition zone is determined according to the dome span, a wooden centering is prepared to define the base

Keywords: Transition zone in Turkish Architecture, transition element, the belt of Turkish triangles, geometry, material, construction technique.