Seismic performance evaluation with different assumptions and comparison of a real building which was exposed to 2011 Van earthquake

Turkey is surrounded by three major African, Arabian and Eurasian plates, and mainly situated on the Anatolian plate. These plates create three major fault lines throughout Turkey, and they are called the North Anatolian Fault (NAF), Northeast Anatolian Fault (NEAF) and the East Anatolian Fault (EAF). As a result of this seismicity in Turkey, a large position of the country is in first-degree earthquake zone. Many regions of the country suffered and affected by these earthquakes throughout the centruies. Besides the fact that Turkey is located along an active earthquake belt, the secondary reason behind the massive damages by the earthquakes in our country is because the buildings haven't been designed – no matter in what year - by taking into account of the impacts of the earthquakes and they haven't been constructed as earthquake resistant. First and foremost, the seismic performance of existing buildings should be assessed in order to reduce the damages by the probable earthquakes that may occur in the country. The seismic performance of a building is a new concept in Turkey and for the first time it has taken a place in Turkish Seismic Code 2007 which has been created by adding some annexes to the Seismic Code 1997. Adding a new chapter in this code as Chapter 7, 'Evaluation and Invigorate of the Existing Buildings', has opened a new field of application for earthquake engineering. The Requirements for Buildings to be built in seismic zones 2007 differs slightly from the steps to be applied to determine the seismic performance levels of existing buildings and building - type structures which are described in details in Chapter 7. The reasons are the uncertainties regarding; -depending on the construction year- the limitation on the information,which should be gathered from an existing building to determine the seismic performance level,the issue whether the building is built under the construction regulations of the period and the materials used in the building. Due to those specific reasons, while assessing the existing buildings and building type structures, we should examine these buildings under more adverse circumstances in comparison to the recent buildings. According to the Chapter 7 of Turkish Seismic Code 2007, the seismic performance analysis procedures of existing building are classified as linear elastic (equivalent lateral load method, mode superposition method); non-linear analysis (pushover analysis with equivalent lateral load method and mode superposition method) and non-linear time history analysis. The main purpose of this linear analysis procedure is to reach reliable results by combining linear analyses with capacity principles in order to determine the real seismic performance of buildings. Nonlinear analysis methods are more rigorous in evaluating the seismic performance of buildings than the linear procedures since they allow redistribution of internal actions in the post-elastic range. On the other hand, linear elastic analysis methods are preferred in practice since less effort is required to obtain the results. In addition, the calculation procedures of linear elastic analysis are straight forward and more practical. The accuracy of linear elastic procedure can be improved by using the capacity principles. The efficiency of this method can be tested by comparing the results of nonlinear procedure by the results of linear elastic analysis. The main objective of this thesis is to assess the seismic performances of the selected case study- building with three different models by using linear elastic procedure step by step as indicated in Turkish Seismic Code (2007). Reinforced concrete frames with infill walls are a prevalent structural system in Turkey. If the infills are properly distributed throughout the structure and properly considered in the design, then they usually have a positive effect on the seismic response of the structure. On the other hand, adverse impact can be caused by irregular positioning of the infills in plan and in elevation. A soft-storey collapse is typical for infilled structures in which the infills are missing in ground storey. The infill walls are ignored during the design and calculation of buildings due to modelling of infill walls are hard and complex. Although infills are neglected as a structural element in the calculations, experimental studies conducted for years and investigations revealed that, infills increase the strength, in-plane stiffness and consequently reduce the natural period of structures. But simply, infill walls improve the lateral behavior of the reinforced frames they fill up. In Turkish Earthquake Code, infills are taken into account only for the calculation of the dead load, however they do not affect dynamic properties of building like stiffness, fundamental period and damping. The presented master thesis is composed of six chapters and the first part is designated for the brief explanation of the subject. The aim and the scope of the thesis explaned in this part. The second chapter includes general information about performance assessment principals of existing buildings as specified in Turkish Seismic Code 2007 Chapter 7. In the third chapter, the important effects of infills on the variation of building loads and building dynamic characteristics are highlighted. On the other hand in the same chapter, several techniques of numerical modeling infills with reinforced concrete frames are presented. These suggestions are mainly the Equivalent Strut method and Finite Element method. In the fourth chapter numerical, investigation is presented in which the seismic performance of the three diffrent models of a reinforced concrete building which exposed to 2011 Van earthquake, analyzed according to the Turkish Seismic Code (2007). In the first model TSM-1 reinforced concrete frame is modeled in as given its own static project by using SAP 2000 structural analysis program. Unlike the first model TSM-1, the second model TSM-2 reinforced concrete frame is modeled by adding a storey (height of 2,8 m) with additional balcony at the building's lateral facade which reflects the real existing situation of the building. In the third model called as TSM-3, the stiffness of the infill walls are modeled by using equivalent compression struts in addition to the second model. For determining the seismic performance of three diffent models in this section, the linear elastic method is used. (as suggested in Turkish Seismic Code 2007- Chapter 7). In the sixth chapter, the conclusions of the thesis study are summarized. In this chapter, discussions about 3 different models are given. Aproach and suggestions for future studies are presented.