Visual analysis of vault structures in the landscape of historical squares of Iran with emphasis on Safavid and Qajar periods

Arched structures, especially vaults, as one of the most widely used structural elements in traditional architecture, are of particular importance in the perspective of historical settlements.
However, most of the research in this field has been devoted to historical and technical issues and so the visual functions of this element has been stayed hidden behind the role of its structure.
This paper tries to understand and explain the role of vault structures in organizing the landscape of historical urban Squares, to provide solutions appropriate to contemporary needs for designing and organizing squares.
The process of this research began with library studies and continued with the sampling through field studies.
In this regard, first, the eight squares chosen as case studies were divided into three types based on the type of function of vault structures in their facade: «portico», «room and bulkhead» and «bulkhead».
Then, the role of these elements in covering the facades in both vertical and horizontal directions in both micro and macro scales was analyzed.
The examined issues at the micro-scale include: how the rhythm was created, the connection of the walls to the surrounding buildings and the entrance of the square, and the connection of the walls to each other in the body of the square.
The results of the research indicate the use of three methods based on «complete vault», «buildings and entrances» and «combination of complete vault with half- vault « in order to create rhythm in the facades.
In addition to creating rhythm, « combination of complete vault with half- vault» has also been used to connect the facades of the square to the surrounding buildings.
Analyzes also reveal four methods used to link the facades of squares with each other, including « complete vault «, « half- vault», «diagonal with a 45 degree angle» and «disconnected».
Then, how to place two stories of the square on top of each other in a vertical direction was studied.
Here, by examining the general structure of the upper floor, the roots of the creation of the outer corridor on the first floor of the squares are discussed as an arena for access and observing the center of the square.
Then as a result of studying the role of vault elements on the scale of whole square, we found a triple pattern for the composition of these elements in the facade: «creation of confinement», «building a foundation for visual emphasis» and «visual emphasis».
Finally, due to the fact that decorations are one of the important features of Iranian-Islamic architecture, various methods of decoration, including «brickwork», «karbandi», «tiling», «mural» and «column» and their position on the surface of vault structures are analyzed and introduced to explain the robust background for contemporary improvement and design.