Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü
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Browsing Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü by Subject "Buildings -- Earthquake effects."
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Item Alternate representations of dynamic properties and loading(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2014., 2014.) Gülenç, Caner.; Tanırcan, Gülüm.; Aydınoğlu, M. Nuray.This study covers three main topics, which are directly related to dynamic behaviour of structures, namely, representation of mass, damping and loading. These three properties of equation of motion are generally represented by widely accepted approaches. In this thesis, such representations are discussed via comparisons with infrequently used representations and viability of them is investigated. For case study, 50-story core wall structure is chosen. First topic discussed here is mass representation. Indisputably, the most accepted assumption for mass representation is lumped mass approach, which is very practical to construct the matrix or, at least, easy to understand the concept of. Another representation, not common one, consistent mass approach derived by a similar procedure in the method for derivation of stiffness coefficients. Consistent mass matrix has off-diagonal terms as distinct from lumped mass matrix. Since the core wall has a continuous form, it is reasonable to represent its mass distribution with consistent mass approach, which takes into account coupling terms. Effects of consistent mass representation on dynamic response of a 50-storey core-wall tall building are investigated. Second one is damping property which may be evaluated as one of the most controversial aspects of structural dynamics. As it is not possible to derive a damping matrix from the element cross section properties and material properties directly, proportional viscous damping matrix is generally used instead, which is defined in terms of modal damping ratios at certain anchor frequencies. However, viscous damping model has a significant deficiency associated with the energy mechanism. Studies based on experimental data show that dissipated energy per cycle of an oscillating system is essentially independent of the excitation frequency as opposed to dependency inherent in the viscous damping model. Such damping model is called rate-independent or structural damping, which is conveniently modelled in the frequency domain through complex stiffness matrix. One of the aims of this study is to observe the effects of such an alternate damping model on the linear seismic response of a tall building. To this end, a 50-story core-wall tall building system is investigated. Drift and total acceleration response characteristics for a set of earthquake records are obtained from the analyses conducted through Fourier Transform. Last concept, probably the most innovative idea of this study, is related to loading part of equation of motion. It has been long applied that ground accelerations are used directly as force by multiplying floor masses, eventually, relative response quantities are obtained. The underlying idea of this loading concept is based on pseudo-static transmission assumption, which presumes that base displacement, in any time instant, is transmitted throughout building statically and naturally, such movement does not deform the structure. One of the aims of this study is to investigate viability of this concept. The motivation is based on the idea that if the building is tall enough, is it possible to be transmitted of base displacements throughout the building without generating any significant deformation? For this reason, absolute response and relative response quantities of the 50-story core-wall are obtained by using acceleration and displacement loading concepts respectively. Comparative results are given at the end.Item Comparative evaluation of codes and regulations in Turkey for earthquake performance assessment of existing buildings(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2020., 2020.) Dede, Şahin Özdoğan.; Hancılar, Ufuk.New Turkish Building Seismic Code published in 2018 has been officially in force since January 1, 2019. The new code introduces significant changes not only in the countrywide seismic hazard maps but also in structural modeling and analysis issues for the design of new buildings as well as in the definition of performance objectives and assessment methodologies for existing buildings. In this study, a comparative earthquake performance assessment of a reinforced concrete building in Istanbul is presented. The building, which was constructed in 2006, has four stories rising above a basement floor. The lateral load-carrying system consists of moment-resisting frames with two shear walls around the staircase. Although it is assumed that the building was designed according to the provisions of the Turkish Building Seismic Code-1998, it was identified as a risky building last year based on the simplified guidelines by the Ministry of Environment and Urbanization (Riskli Yapıların Tespit Edilmesine İlişkin Esaslar-2013). Earthquake performance of the study building is evaluated for the requirements of the new Turkish Building Seismic Code (2018) and of its previous version (2007) as well. For this purpose, a three-dimensional finite element model of the building is elaborated on the basis of the blueprints. Geometrical and material characteristics are further verified by the reports on in situ measurements and field tests. Linear and nonlinear static and dynamic analyses procedures are implemented, and a detailed assessment of the building against the performance criteria by each code is performed. Additionally, the building is assessed on the basis of the updated guidelines by the Ministry of Environment and Urbanization (Riskli Yapıların Tespit Edilmesine İlişkin Esaslar-2019). Outcomes of the earthquake performance assessments are presented comparatively, and the differences/changes among the codes and guidelines are highlighted.Item Development of a low-cost aseismic base isolation device for protection of structural systems from damaging effects of earthquakes(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2009., 2009.) Kesti, Mustafa Gökhan.; Erdik, Mustafa.Due to the killing thousands of people in the twentieth century and seismicity of our country, earthquakes are one of the most important natural hazards for our country. Therefore the earthquake resistance of structural system plays central role for earthquake protection. This M.Sc. thesis research’s concern is to illustrate some base isolation techniques and to propose a base isolation device to improve the earthquake resistance of structural systems. The so-called Ball-N-Cone (BNC) aseismic base isolation device is experimentally studied and results are given.Item Dynamic response characteristics of the Sapphire building in Istanbul estimated from earthquake and wind data(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Savaş, Hakan Doğukan.The number of tall buildings has been increasing all around the world due to the current population growth and limited space in city centers. After major earthquakes, countries located in earthquake-prone areas face catastrophic conditions. In addition to building damages, deaths, and injuries, financial losses due to business interruption are also an important part of overall earthquake losses. Therefore, buildings home to organizations such as financial institutions, health care facilities, governmental buildings need to remain functional following an earthquake to constrain financial losses and secure public services. The condition of structures can be estimated by evaluating the change in the in-situ dynamic characteristics of the structures in real time day by day. In this study, the dynamic parameters of the Sapphire Building during strong wind and earthquake records are estimated in the time and frequency domain. Earthquake and wind events were selected from catalogs derived from Bogazici University Kandilli Observatory and Earthquake Research Institute Regional EarthquakeTsunami Monitoring Center and Bogazici University Kandilli Observatory and Earthquake Research Institute Meteorology Laboratory. In time domain analyses, correlations between peak accelerations, velocities, displacements; and magnitude and distance are estimated. The effects of faraway earthquakes on displacement time histories and damping are also investigated. Average drift ratios, computed from both wind and earthquake records, are compared with the limitations provided in the codes. In the frequency domain, natural frequencies, damping and mode shapes are identified by means of spectral analysis for wind and earthquake data. The result of wind and earthquake events on the Sapphire building are compared.Item Re-evaluation of earthquake performance and strengthening alternatives of Hagia Sophia(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2008., 2008.) Kırlangıç, Ahmet Serhan.; Durukal, Eser.Static and dynamic linear analyses were carried out to evaluate the structural behaviour of and to propose strengthening strategies for Hagia Sophia. A Finite Element model of the structure was used for this purpose. While linear static self-weight and eigenvalue analyses were performed to ensure that the finite element model represents the structure, response spectrum analysis was used to obtain the deformation and stress distributions for determining the regions where intervention is needed. Response spectrum analysis revealed that main arches, semidomes and domebase exhibit high stress concentrations. These particular elements were the target zones for intervention. Two main strengthening strategies were considered: i) Retrofitting the main arches with post-tensioned bars, ii) Wrapping the structural elements with fiber reinforced polymers FRPs. These two strategies were modelled and changes in the structural behaviour were observed. The analyses revealed post-tensioning as a more effective approach as compared to wrapping the structural elements with FRP laminates.Item Shake table tests of a 1/4 scaled mass concentric three storey steel structure isolated by a hybrid passive control system(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Yenidoğan, H. Cem.; Uçkan, Eren.Objective of this study is to investigate the effectiveness of a hybrid isolation system for a three-storey mass concentric steel structure. The isolation system consists of 2 elastomeric bearings and 4 flat sliding bearings, which are located below the central and corner columns, respectively. A 1,4 scaled isolated model of the structure has been tested on a shake table under real earthquakes and sinusoidal base motions. Measurements were taken at structural points and at base slab level. Two types of high damping elastomeric bearings, one with low shear modulus and the other with high shear modulus, were tested to see the effects of different target isolation periods. A numerical model for the structure was developed and calibrated by the data from the experimental studies. In this dissertation effectiveness of the hybrid isolation system is verified by comparing the results obtained from isolated and fixed base models.