Surveying and conservation proposals of two iron roof structures of Imperial Mint buildings

Historical buildings are important in terms of architecture overview and also history of construction techniques. Because of this reason both of architectural and structural elements of historical monuments and buildings must be conserved. Time shows that may historical constructions deteriorated and collapsed due to natural disaster, strength degradation, non-weather protected conditions, etc. Therefore diagnosis of the existing situation of materials and structural understanding is important for architectural conservation. Iron is an integral part of human history, as can be safely argued by the technical capabilities opened up to artisans, craftsmen and architects by its becoming available, which warranted an entire age to be named after it. Iron architecture, born out of technological innovations and the necessity to address new architectural needs and problems, brought about significant changes in the world of construction. In the context of this dissertation, the use of iron in Ottoman Architecture's construction has been investigated. The case study is two iron roof structure of Imperial Mint Buildings. The complex is located on the first courtyard of Topkapı Palace. Imperial Mint was established in Topkapı Palace during the 16th century. The buildings have multi-layer intervention since its established, according to technological development on mint technology. The complex had been continued mint function until 1967 and new factory building were built on Balmumcu. After moving the buildings were used for some cultural activities for a few years. And later the buildings remained functionless form many years. Due to become non-functional, the buildings have been deteriorated during the years. Most of the buildings have been exposed the weather condition because of dilapidation of roofs, windows, etc. Number 14 and 15 buildings, which are the case study subjects, are located second courtyard of the complex. Number 15 building was built in second half of 18th century and Number 14 building was built in end of 19th century. Both of the buildings have authentic iron roof structure. There iron roof structures are initial whole iron structural elements on Ottoman Architecture. The iron structural elements are unique examples that show iron construction technology and recruitment process on their era. They show authentic connection details, dimension of sections, manufacturing methods. The last repair was done in 1996 and authentic iron roof structures were preserved. The new raised steel roof structure and roof covering were placed top of the building with avoiding damaging on original roof structures. The current survey, restitution and restoration projects were prepared by Minister of Culture an Tourism in between 2011 and 2015. All the projects were approved by Cultural and Natural Heritage Preservation Board. Protection and completion of roof structures are recommended on restoration projects. The lack of structural understanding original detail and existing situation of iron roof structures is the main point of conservation issue. The general objective of this dissertation is to analyse and conclude on the use of iron as a construction material in case study buildings, both as an original structural part and as an architectural elements. The research mostly based on literature overview, archive research, inspection and diagnosis, minor destructive testing and analysis. Number 14 and Number 15 buildings have similar plan scheme. They have main rectangular shape space. The main outer walls are brick masonry on Number 14 building and stone masonry on Number 15 building. The iron roof structures are placed on top of the masonry walls. Number 14 building has gable roof and Number 15 building has row of gable roof. The buildings have authentic masonry furnaces from initial period. The furnaces show that the buildings were taken part of production process. Both of the buildings have wrought iron elements on roof structures. Number 14 building has two main iron truss, tree lines of iron purlins and iron rafters. Two square shape slender iron columns are located under the middle of trusses. Number 15 building has tree double row square shape slender iron columns, tree lines square shape iron beams and triangle form iron rafters. The detailed structural geometrical survey were taken during the dissertation period. All iron structural elements were measured and documented. And also the archive and literature researches, minor destructive tests, historical survey and structural analysis were done. Tree specimens were taken from iron structures of building. Tensile test were performed in İstanbul Technical University and the specimens were examined on electron microscope in Bogazici University. The mechanical, chemical and physical properties of iron were obtained from test results. The mathematical modelling was completed according the properties and dimensions of iron structure. The existing situation was analysed for two condition. First condition is only iron roof structure without any roof covering. Second is iron roof structure with timber covering, isolation layer and tiles. The snow load was considered on the analysis for second condition. The results were compared by physically, chemically, mechanical properties and bearing capacity for Number 14 and Number 15 buildings. Wrought iron materials are very similar mechanical properties for both buildings but structural designs are different. Different structural parts of roof have bearing capacity problem. The iron beam's structural capacity does not enough on Number 15 building and the iron truss elements' structural capacity does not enough on Number 14 building according to second condition analysis. All the existing elements for both structure have enough bearing capacity according to first condition. Conservation and intervention proposals are compared on this dissertation. Mainly interdisciplinary advanced study, additional non-destructive and minor destructive tests, taking survey of unattained connection details, modelling of whole structure both masonry and iron structure are suggested. The local codes for masonry and steel structures and their efficiency for historical buildings are discussed. Conservation and restoration of historical structures are disciplines that require specific training. The consideration of historical value, respect of architectural value, removability, durability, compability, bearing capacity are important for taking decisions.