Dynamic properties of the historic minarets and their earthquake performance

Historical structures as being cultural heritage, endured all the environmental and human hazards for centuries and carried the cultural, sociologic and economic aspect of its age of construction to modern-day. Protection and preservation of monuments and historic buildings has been seen as a civic duty and as a part of our social responsibility. Thus, this research and thesis focus on the historic minarets which are most exceptional symbols of the religion of Islam. Preservation of the historical structures, which carry a monumental value and reflect the economic and technologic state as well as cultural and characteristic features of its age, is highly important due to the fact that they help to sustain the collective memory, foster the sense of unity and solidarity and remind people the common history of the community. Religious buildings which is a part of the urban fabric, together with fortresses, mansions, public houses, castles, caravansaries, bridges, houses, waterfronts and townhouses, bares an important monumental value as cultural assets of the whole humanity. With their special structural form, which distinguishes them from other historic buildings, Minarets can be commonly found in Turkey. The fact that they managed to survive for centuries even though they have faced many natural hazards, especially seismic waves, shows that they have a peculiar and health structure. Considering the fact that Turkey is located on a seismic belt, understanding the reactions of the historic minarets to seismic waves is important for them to survive for the future generations. It is a necessity to protect our historical buildings, which are an important part of our values and reflection of our culture, by taking all the necessary measures against the natural hazards and environmental factors. Besides presenting the material specifications and architecture of the historical buildings, it is essential to do the modelling of those buildings in a way that it reflects the correct results and the true nature of the building, conducting the pattern analysis and in this sense, as a part of the preemptive action, making the necessary renovations and structure reinforcement. In order to get over an earthquake with the least damage, historical buildings should go through regular renovations and restorations which is conducted in line with the nature of the building. Historical buildings become vulnerable to the damages caused by the earthquakes, together with the modern buildings, due to misuse, poor maintenance and restoration. In order to properly determine the risks that the historical buildings carry against earthquakes, it is paramount to determine the constructional problems of its load-bearing systems, identify the research and examinations to be conducted, establish the basic rules of the calculations on the seismic and vertical loads, determine the solutions in light of those founding and conceptualizing and executing the project. In the first chapter of this work, a general evaluation on the topic is presented. In the second chapter, the importance of the historic monuments and buildings, the factors which may cause the process of decay and disfigurement in those buildings, the effects of earthquakes on historic buildings and the methods of protection and preservation are briefly touched upon. In the third chapter, the purpose served by the minarets are examined by touching upon which sorts of structures inspired their builders and historical evolution of them during the early ages of Islam, Turkish-Islamic Period and the Ottoman period. In the fourth chapter, construction materials used on minarets especially during the Ottoman period are mentioned. In the fifth chapter, the mosques of the minarets which were examined in this work are briefly covered. In the sixth chapter, an outline of the sections of the minarets are given and a modelling study was conducted on them for relievo and scaled drawings. Solid modelling of the dimensioned minarets is also made in SAP2000 static analysis program and touched upon in this chapter. In the seventh chapter, the largest earthquakes ever recorded in Turkey are briefly touched upon. A special examination is made for the Kocaeli Earthquake in August 17, 1999 which was the largest earthquake recorded in Turkey in the last 20 years, Earthquake of Düzce in November 12, 1999 and the Earthquake of Van in October 23, 2011. Additionally, time history data analysis is made for the mentioned earthquakes. In the eighth chapter, the dynamic analysis of the minarets is examined in this work under the 3 mentioned earthquakes and minarets likely performances are touched upon. Additionally, charts that show the mass participation ratio, period and frequency are presented and deformation situation of the buildings are mentioned. Natural period of the buildings and the dominant soil periods related to the earthquakes are compared and the findings are presented in this chapter. The dead load of the minarets and the tensile and compressive loads of them under effects of earthquakes are analysed. Furthermore, the limits of the resonance at the peak of the minarets are determined and presented as a chart. In the ninth chapter, with different number of balconies on them and different geometrical features like height, body diameter and wall thickness, two minarets of the Süleymaniye Mosque with two and three balconies and one minaret of Ramazan Efendi Mosque with one balcony are examined and their time history dynamic analyses are made. In those analysis, the time history data of the 3 different most devastating earthquakes recorded in the last 20 years in Turkey, are used in order to examine the motion and tensile force findings of the analysis. In this thesis work, it is aimed to evaluate the risk factors in the historic buildings related to earthquake forces and technically and scientifically identify them, show the findings of the research and list the possible solutions.