M.S. Theses

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Time - dependent seismic hazard assessment for the north and east Anatolian faults
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2022., 2022) Koca, Cem.; Şeşetyan, Karin.
Until now, many probabilistic seismic hazard assessment (PSHA) studies have been performed for Turkey. However, except in a limited number of cases, character istic fault source modeling was not used. Since the North and East Anatolian Faults (NAF and EAF) have a tendency for rupturing in characteristic earthquakes, the first objective of this research is to develop a sound hybrid characteristic recurrence model for the NAF and EAF. The so-called hybrid model involves a composite characteris tic model (i.e., an exponential part for the smaller and a characteristic part for larger magnitudes) developed for each segment combined with a characteristic recurrence pro posed for multi-segment ruptures. Two different hybrid earthquake recurrence models with time - independent (or Poissonian) and time – dependent (or renewal) character istics are developed. By means of the renewal hybrid model, the effect of some seismic gaps along the NAF and EAF on seismic hazard is assessed, which is the primary purpose of the thesis. On the other hand, these two models have also given the oppor tunity to evaluate the results of the fully exponential model of the NAF and EAF. The comparison between different earthquake recurrence models developed for the NAF and EAF yields interesting results. Fully exponential model usually produces over estimated seismic hazard compared to the Poissonian hybrid – characteristic model. Slip deficits on some fault segments can increase the seismic hazard dramatically if the results of renewal hybrid model are considered. Although the overestimated results of fully exponential fault source model can compensate the high hazard based on renewal hybrid model, depending on the amount of slip deficit, the time – dependent hazard may exceed the hazard obtained by the fully exponential model. In cases where there is a considerable amount of slip deficit on a fault, a time - dependent seismic hazard model should be developed to deal with the worst-case scenario.
Epistemic uncertainty in the analytically derived fragility functions : multiple stripe analysis versus cloud analysis
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2022., 2022) Önder, Zeynep Eda.; Hancılar, Ufuk.
This study aims to examine the effects of epistemic uncertainty arising from dif ferent analysis approaches on the derived fragility functions. To this end, fragility functions are developed by using two different methods namely multiple stripe analysis (MSA) and cloud analysis, and compared for low-rise and mid-rise (3 and 6-story), re inforced concrete (RC), moment-resisting frame (MRF) buildings designed as per the Turkish Seismic Codes (TSC) published in 1975 and 2018. Each building’s prelimi nary design complies with the minimum requirements specified in the relevant seismic codes. A total of four buildings are studied considering different heights and different seismic codes. The OpenSees Program (the Open System for Earthquake Engineering Simulation) is used to perform nonlinear dynamic analyses of the structures. While spectral displacement (Sd), spectral acceleration (Sa) and peak ground acceleration (PGA) are chosen as intensity measures, maximum inter-story drift ratio (MIDR) and top displacement (Dtop) are selected as engineering demand parameters. For the dam age state definitions through threshold values on the EDPs, nonlinear static (pushover) analyses are conducted to pick the limit values of top displacements from the idealized pushover curves whereas limit values for MIDR are drawn from the Hazus MR4 Tech nical Document. For MSA, 11 stripes and 22 pairs of earthquake records for each stripe are used, while 44 sets of record pairs are used for cloud analysis. Fragility functions for the aforementioned buildings are developed by using two methods and compared to account for the epistemic uncertainty in the derivation of fragility functions.
Numerical modelling of ground motions in Eskişehir basın
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2022., 2022) Akpunar, Lütfü İhsan.; Tanrıcan, Gülüm.
Eskişehir basin is located at the boundary of central and western Anatolia tectonic regions. Between two active faults it extends in EW direction with two open ends. So far deep velocity structure of the basin has not been well constrained however, average shear wave velocity for the top 30 m and sedimentary thickness estimations are available at various locations of the basin (e.g.,T¨un et al. (2016); Yamanaka et al. (2018); Ozel et al. (2020)). Number of strong motion recordings is rather limited due low seismicity of the region. The largest magnitude event that has ever been recorded within 150 km is the 2011 Simav Earthquake (Mw 5.9). Eskişehir city, with a popula tion close to a million people, has been expanding towards to this sedimentary basin. Long period ground motion is the concern of large scale structures that will be built at this region. Here we first present observed features of strong ground motions of this event recorded in the Eski¸sehir basin. Firstly, we observed that ground motion from the 19.05.2020 Mw 5.9 earthquake is governed by Rayleigh waves at periods longer than 0.5 s. Retrograde motion is visible almost at all basin- recordings. Among recorded waveforms, PGA and PGV of a basin- edge station (#2610 AFAD station) are formed by Rayleigh waves at periods 1 s. The longest significant duration of recordings is as high as 53 sec. Recorded spectral acceleration for 5% damping at spectal periods longer than 1 s is much higher than the one predicted by region specific ground motion prediction models. In the second phase, we showed formation of an experimental basin geometry utilizing linear interpolation of predominant frequencies at 95 measurement points. Dimensions of the model are 43 km \ 27 km \ 15 km. Basin layer continues across the entire model in EW direction, but bordered by northern and southern hills to mimic the geographical environment. Maximum depth is about 600 m. In the last phase we investigated the 3D wave propagation of small magnitude events, 17.01.2015 Mw 4.3 and 18.09.2015 Mw 3.7, occurred at northwestern part of the region and center of the basin, and compared with observed recordings for a possible validation of the velocity model. The computer code utilized in simulation relies on a finite difference modelling using staggered grids with nonuniform spacing. Ground motion simulation of the Mw 4.3 event reveals that the current velocity model overestimates the velocities in the eastern part of the basin in the NS direction, where E-W direction synthetics are generally smaller than the observed ones. On the other hand, synthetic velocities agree with observed ones at basin-center stations in the west. These findings suggest that more careful definitions of basin boundaries are necessary for the future models. Comparison of 1D and 3D simulation results also suggest that a 3D velocity model may produce longer and -more realistic- duration ground motions. The final step is to perform a blind simulation for the 20 February 1956 Mw 6.5 earthquake. The source was modeled by considering the ambiguities in the source parameters. The previous research was compiled to deal with unknown information about the mechanism and location of this event for consensus. We have compared the simulation outcomes with GMPEs models. The numerical simulation results yielded higher outcomes than estimated spectral ordinates by GMMs.
Effects of site improvement technique on seismic performance of geotechnical structures
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2022., 2022) Demirtaş, Bilge Sultan.; Edinçliler, Ayşe.
Earth-retaining structures are widely used in the man-made environment and compose the significant constituents of infrastructural systems worldwide. Besides, they have been constructed broadly in seismically active regions. Earthquakes can cause a lot of damage to geotechnical structures. The prevention of failures in these structures is an important issue. Cost effective remedies can be applied to retaining structures in order to prevent them from failing under seismic loading. The use of lightweight materials behind the wall as a cushion layer is one of the methods to improve the seismic performance of the retaining system. The objective of this thesis is to investigate the effects of cushion type on the seismic performance of retaining walls by performing shake table tests. The experiments were carried out with a 1/25 scaled retaining wall model with or without a cushion layer. In the experimental study, the cushions were considered as EPS geofoam and a mixture of tire crumb and sand. Additionally, various parameters, such as cushion thicknesses, EPS geofoam densities, mixture ratios of sand-tire crumb mixture, and input characteristics, are also evaluated. The results were examined by comparing the cases having a cushion layer with the case without a cushion layer depending on mentioned parameters. The evaluation of the results indicates that the seismic performance of the retaining wall is very sensitive to cushion type. It is observed that the EPS cushions are more effective than the sand-tire crumb mixtures to improve the seismic performance of the wall. Additionally, the use of cushion layer with higher thickness can be an effective solution to improve the seismic performance of the retaining wall, prevent the future failure of the retaining structure, and mitigate earthquake hazards.
Seismic evaluation of Bolu viaduct 1
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake research Institute, 2006., 2006.) Candan, B. Tolga.; Aydınoğlu, M. Nuray.
A thesis is presented on the seismic evaluation of a viaduct using non-linear analysistechniques. The Bolu viaduct is a 2-3 km long seismically isolated structure with two parallelbridges each with a span length of 39.2 m and pier height of maximum 49 m that was nearly complete when it was struck by the 1999 Duzce earthquake in Turkey. With the design basedon AASHTO standards, it suffered complete failure of the seismic isolation system andnarrowly avoided total collapse due to excessive superstructure moment. After investigationsthe retrofit of the viaduct had been decided due to the study carried out by Michele Calvi and J. Nigel Priestley. This thesis concentrates on the retrofitted structure of Viaduct 1 by non-linear time historyanalysis.
Investigation of failure modes and mechanisms of Alibey Earth Dam by solid-fluid coupled nonlinear dynamic finite element simulation
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Parker, Ahmet Alper.; Siyahi, Bilge.
In this study, earthquake resistance of Alibey Earth Dam was investigated. Darn was modeled with four node plane-strain finite elements and displacement-pore pressure coupled finite element analyses were performed. Nonlinear material models such as pressure dependent and independent multi yield materials were implemented during the analyses. Transient dynamic finite element analyses were performed with Newmark method. Newton-Raphson solution scheme was adopted during the solution of the equations. Liquefaction and/or cyclic mobility effects were considered during the analysis. For the finite element analyses OpenSees (Open System for Earthquake Engineering Simulation) framework was adopted.
Strain based performance evaluation charts for rectangular reinforced concrete columns in nonlinear analysis of structures
(Thesis (M.S.)- Bogazici University. Kandilli Observatory and Eartquake Research Institute, 2005., 2005.) Şadan, Oğuz Bahadır.; Aydınoğlu, M. Nuray.
Several methods and criterion are being used recently in determination of the deformations occurred in structural elements of a building and performance evaluation of these structural elements under earthquake motion using nonlinear analysis. Performance evaluation of structures under nonlinear earthquake loading using material strains, rather than the rotations as commonly used in other seismic codes (FEMA356, ATC40, EUROCODE8 etc.) is the basic subject of this study. Performance evaluation using material strains is also being mentioned in Chapter 13 of New Turkish Seismic Code Dra3. For performance evaluation using member strains, Strain Based Performance Evuluation Charts for rectangular reinforced concrete columns have been formed which bring easiness by omitting several cross sectional analysis in order to transform rotations into strains. These Strain Based Performance Evaluation Charts are intended to be very useful for the structural engineers who will practice nonlinear analysis using New Turkish Seismic Code in the future. However it should be noticed that these charts are formed only for rectangular reinforced columns with limited concrete-steel grade combinations. Therefore further studies should be performed for other combinations and beams.
Seismic performance evaluation of public school buildings in İstanbul metropolitan area
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2005.) Ekser, Burç.; Yüzügüllü, Özal.
Earthquake resistance of school buildings deserves special attention with respect to seismic safety because of their occupancy characteristics and their importance to immediate and long-term earthquake disaster relief and recovery efforts. The aim of the study is that the seismic performance evaluation of public school buildings in Istanbul. According to this, in Istanbul, three different types of projects are practiced and evaluated for public schools constructed due to different number of stories and different earthquake zones. besides, these kinds of porjects were analyzed in terms of 1975 and 1998 Turkish Codes. In addition to the seismic performance evaluation of public schools, a preliminary screening procedure was carried out in that study. To eliminate the losses caused by earthquakes, the earthquake resistance of the school building must be examined by quick and easy method which is Rapid Visual Screening Procedure prepared by Applied Technology Council. Actually, the method which was carried out, is classified the earthquake resistance resistance of the public schools and determined a detailed evaluation is required or not.
Development of fragility functions for code conforming low-rise reinforced concrete buildings
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Şenol, Erkan.; Hancılar, Ufuk.
In this study, fragility functions are developed and compared for low-rise (2 and 3-story), reinforced concrete (RC), moment-resisting frame (MRF) buildings, which are designed per the Turkish Seismic Codes (TSC) released in 1998 and 2018, at eight different locations in Istanbul, Turkey. In the preliminary design of each building, the minimum conditions defined in the corresponding seismic code are followed. Moreover, the capacity design principles are taken into consideration as defined in the seismic codes. To increase the representa tiveness of the dimensions (i.e., footprint, structural member dimensions, story height) of the buildings, the past studies about the characteristics of the low-rise buildings in Turkey, and the structural drawings belonging to the existing buildings designed per the corresponding seismic codes are examined and used. Considering eight different locations, two different story numbers, and two seismic codes, a total of 32 buildings are designed and analyzed. The nonlinear analyses of the buildings are conducted by using the OpenSees Software (Open System for Earthquake Engineering Simulation Pacific Engineering Research (PEER) Center Version 3.0.3). The structural elements (beams and columns) are modeled with frame elements. The distributed plasticity (fiber) is considered for the columns whereas lumped plasticity (plastic hinge) is considered for beams. To generate the fragility functions for the buildings, multiple stripe analysis (MSA) together with the maximum likelihood estimation (MLE) method is utilized. Spectral displacement (Sd) and spectral acceleration (Sa) are selected as the intensity measure (IM) parameters whereas the maximum inter-story drift ratio (MIDR) and top displacement (Dtop) are used as engineering demand parameters (EDP). The fragility functions are developed for four damage states which are slight damage, moderate damage, extensive damage, and complete damage. While deciding the limit values of the EDPs for each damage state, we perform pushover analysis to decide the limit values of top displacements from the idealized pushover curves. With regards to the limit values of MIDR, they are taken from Hazus MR4 Technical Manuel, which is defined for low-rise, high-code MRF structures. For MSA, eleven intensity measure levels (stripes) are defined, and for each stripe, 22 pairs of ground motion records are selected and used. To select the ground motion records for each stripe, a code-based target response spectrum is developed for each IM level. By making use of the devel oped response spectra for each IM, 22 pairs of ground motion records are selected from PEER Ground Motion Database for each IM level (stripe). The fragility functions based on the different types of IMs (Sa and Sd) and the different types of EDPs (MIDR and Dtop) are developed and compared for the 2 and 3-story low-rise RC buildings designed per TSC1998 and TSC2018.
Pipeline damage assessment through Monte Carlo simulation
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Bingöl, Ali Osman.; Hancılar, Ufuk.
Earthquakes are one of the most catastrophic events among all the disasters. They affect societies in many aspects including life losses and economic losses. Besides the life losses, a lot of people get injured and become disabled due to earthquakes. As being parts of the lifeline systems in a city, potable water systems, wastewater systems, electricity systems, etc. are vital for human life. The impediments in the serviceability of these lifeline systems, put people’s lives in danger even after an earthquake. Studies to reduce the negative effects of earthquakes and guess the serviceability of a lifeline system after an earthquake has gained major importance. In this study, algorithms to predict the number of damages on the water pipeline system due to an earthquake suggested by both HAZUS-FEMA (2003) and the Ameri can Lifeline Alliance (ALA-2001) are compared. Moreover, the Monte Carlo simulation technique is introduced to these two methods and the results of these methods through Monte Carlo simulation are also compared. To perform the analyses, a generic study of the Zeytinburnu potable water system in Istanbul is examined with four different pipe material types, namely, concrete, bellmouth concrete, steel, and polyethylene under a scenario earthquake generated by ELER software. Concrete and steel pipes have large diameters, whereas bellmouth concrete and polyethylene pipes have small diameters in this study. With these different pipe material types, the effects of being brittle and being ductile materials on pipe failures are also evaluated and compared.
A study on the fragility modeling of mid-rise tunnel form RC buildings for Turkey
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Özen, Uğur.; Akkar, Sinan.
The mid-rise tunnel form RC buildings in metropolitan cities in Turkey and their dynamic behavior against earthquake action are investigated by deriving a representative model. First of all, the compiled blueprints of the tunnel form RC building inventory are categorized into four different groups and their fundamental features are studied statistically. The first group, which is the focus of this study represents general features of mid-rise tunnel form buildings in Turkey. Secondly, the nonlinear structural model of this building is developed based on the code requirements and guidelines to perform push-pull and pushover analysis for obtaining its simplified SDOF version in the MSc thesis of Curic (2021). The results of these two theses will complete and augment each other in a near-future collaborative work. Then, the ground motions selected and scaled to the target conditional-response spectra developed in Curic (2021) are used together with the provisions in the 2018 Turkish Building Earthquake code, 2004 Eurocode, and 2017 ASCE code to assess the structural performance of the model building (through damage states) for developing fragility curves. The observations from this study show that the performance of mid-rise tunnel form buildings can be called as satisfactory under the requirements dictated by the national and international standards. Another observation is that different engineering demand parameters give different performance assessment results. Hence, novel global and local performance demand parameters should be investigated by studying other categories (mid- and high-rise) tunnel form buildings. The variabilities in (1) engineering demand parameters, (2) structural properties such as story number, types of vertical elements, and mathematical model, and (3) the definition of limit states in both local and global performance levels have a significant effect on the fragility curves. These variabilities are taken into account for performance based assessment.
Epistemic uncertainties in probabilitic earthquake hazard models and their effects on the results :|the case of Marmara region
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Perdıbuka, Hülya Yüksel.; Şeşetyan, Karin.
Throughout the history and also in the not too distant past, Marmara region has been a center that hosted several of the most destructive earthquakes around the World. Considering the density of population and building stock and the concentration of economic activities, the performance of comprehensive earthquake hazard assessment studies is one of the essential steps towards the mitigation of the seismic risk in the Marmara region. The seismicity and the earthquake characteristics of this region have been studied extensively in the last decades, and various hazard maps have been created. In the light of the increasing amount and quality of data and new studies on seismotectonic and the developments in the earthquake hazard calculation methods, the need for a regular updating of the earthquake hazard estimates for regions with high seismic activity arises. Therefore, new earthquake hazard maps for specific regions or regions covering many countries are being generated continually. In today’s practice, the use of the probabilistic earthquake hazard assessment method has become a common implementation in the preparation of earthquake hazard maps. However, as opposed to site-specific assessments, large scale regional studies usually investigate the effects of epistemic uncertainties only in a limited way, and in most cases, only the mean hazard outputs are reported. Nonetheless, analysis of epistemic uncertainties in the hazard assessment and reporting of the uncertainty ranges associated with the ground motion estimations can provide valuable insights towards a better understanding of the seismic hazard and consequently of the seismic risk. Starting from this point of view, developing an earthquake hazard assessment model specific to the Marmara region, dealing specifically with the uncertainties associated with the modelling approaches, is quite meaningful when the earthquake history of the region is also considered. In this thesis, in order to examine the effects of uncertainties on probabilistic earthquake hazard analysis results specific to the Marmara region, the Turkish Seismic Hazard Map developed within the scope of the “Update of seismic hazard maps of Turkey (UDAP-Ç-13-06)” project was evaluated. Alternative models were included in the earthquake hazard calculations by obtaining uncertainties related to the data and modelling parameters and combining them in a logic tree structure. Accordingly, hazard maps are obtained for PGA and 5 % damped Spectral Accelerations at T = 0.2 s and 1.0 s for 475 and 2475 years return periods, and uncertainty ranges for the computed ground motion parameters are presented. The sensitivity of the results to the uncertainties associated with different modelling parameters is investigated. The results indicate that, even for the Marmara region, which is one of the best-studied regions in terms of seismic activity and geological structure, the seismic hazard models can be associated with large uncertainties.
Scalar and vector probabilistic seismic risk assessment procedures and their implementation for a simplified mid-rise RC tunnel from building
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Curic, Haris.; Akkar, Sinan.
This thesis implements various scalar and vector methods of probabilistic seismic risk assessment. Methods implemented differ by type of scaling and selection of ground motion records as well as by primary scalar intensity measure (IM) used as ground motion intensity metric. Two different ground motion scaling and selection methods are used, namely stripe scaling and cloud scaling. Conceptual differences between stripe scaling and cloud scaling as well as the differences they produce in risk assessment results are presented and discussed. Different scalar ground motion intensity measures used are fundamental period spectral acceleration (SAT(T1)) and two distinct weighted average spectral accelerations. Weighted average spectral acceleration is a novel intensity measure developed and presented within this thesis. It is shown to be a good predictor of structural response at high intensity levels where structure undergoes intense yielding. Weighted average spectral acceleration enables analyst to set weights to contributions of spectral accelerations at different periods according to their expected importance to structural response. Conditional spectra for ground motion selection are developed for all three considered scalar IMs. Multivariate normal distributions are presented as useful mathematical tools and they are used for various purposes throughout this thesis (conditional spectra, vector IM hazard, structural response modeling, etc.). Maximum likelihood estimation (MLE) based method is also developed for estimation of parameters used for modeling structural response using structural analyses data.
Characteristics of the dynamic response of the Sultan Ahmet Mosque (Istanbul) to earthquakes
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Dönmez, Kökcan.; Çaktı, Eser.
The 400-year-old Sultan Ahmet Mosque is located southwest of the ancient hippodrome in Istanbul's historical peninsula. This historic structure, which has survived from the Ottoman period, experienced many damaging earthquakes in the North Anatolian Fault, especially in the fault segments within the Marmara Sea, since its construction was completed in 1617. The mosque is prominent as a cultural heritage element in the city. Therefore, its primary structural system has been monitoring since 2012. The Structural Health Monitoring system deployed in the mosque consists of ten triaxial (two horizontal, one vertical) accelerometers functioning at a sampling rate of 200 Hz. Sensors were installed as four at the main dome, four at the upper galleries of the pillars, one at the ground level, and the last one on the basement floor. Over two hundred recorded earthquakes between October 2012 and November 2020, whose magnitudes ranging from minor to strong, were processed and assessed through scripts coded on MatLab. Used criteria such as sensor completeness of an event and the signal-to-noise ratio of a recording initially reduced the number of earthquakes. Hence in this thesis, the final catalogue of 103 events was analysed in time- and frequency-domain after evaluating the catalogue statistically as functions of magnitude, distance, and azimuth. In the time domain, acceleration, velocity and displacement peaks were obtained and assessed individual- and group-based. Their various relations with earthquake magnitude and amplitude were also examined. In frequency domain analyses employing modal approaches, the dependence of dominant frequencies on time, temperature, earthquake magnitude, and ground motion amplitude was investigated. Particle motions and mode shapes for the selected largest-amplitude events were identified and depicted. Finally, the existence of soil-structure interaction and the rocking vibrations in the structure were investigated.
Synthesis of earthquake ground motion at the 1915 Çanakkale Bridge :|stochastic simulations with a regional path duration function
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Büyükçapar, Numan.; Tanırcan, Gülüm.
Strong ground shaking duration has got to be taken into consideration realistically in ground motion simulations as it is a key parameter affecting structural damages. Total duration of an earthquake comprises source and path properties. Among them path duration which is one of the most important parameters for use in stochastic simulation studies has long been defined as multilinear functions of distance modelled with regional or global earthquake ground motion recordings. Up-to-date path duration models available in the literature are based on global (PEER-NGAWest2) or regional (such as NEAmerica, Japan) strong motion database. Therefore, they represent either a global estimation or can be used only for certain regions. Turkey-specific path duration-distance function is absent in the scientific literature. The main purpose of this thesis is to fulfill this absence and propose a path duration-distance function utilizing the abundant strong motion database of Turkey as well as performing stochastic simulation of strong ground motions at the 1915 Çanakkale Bridge by using path duration function that describes the behavior of Turkish earthquakes. For the latter part of the study, a stochastic simulation method of Motazedian and Atkinson (2005): EXSIM is utilized. Effect of generic and site-specific local site amplification on the simulation is another subject that is investigated in the thesis. Subsequent to this suggestion, the said original method, which is also present on the SCEC (Southern California Earthquake Center) Broadband Platform, was improved by Boore (2009) and Assatourians and Atkinson (2012). Following the analyses which are intrinsic to above-mentioned parts of the study, the obtained regional path duration function has been discussed in detail, and simulations that have been performed throughout the thesis have been thoroughly assessed and presented.
Experimental evaluation of natural vibration frequencise of un-damaged and damaged reinforced concrete buildings with laser vibrometry
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Ertürk, Sefer Ömercan.; Çaktı, Eser.
In this study, a laser vibrometer recently acquired with the support of the Boğaziçi University Scientific Research Projects Fund is tested and validated in laboratory and field conditions. It has been used in a survey carried out in Istanbul about fundamental frequency assessment of 103 tall buildings. The records obtained are analyzed, and a fundamental frequency – building height relationship for tall reinforced concrete buildings in Turkey is proposed. Furthermore, the laser vibrometer has been used in a survey for the assessment of fundamental frequencies of damaged and undamaged buildings in İzmir following the 30.10.2020 Samos-Sığacık earthquake. The records taken from 38 buildings are analyzed, and characteristics of fundamental frequencies of buildings in different damage states are discussed.
Effects of soil reinforcement on seismic performance of low-to-medium rise buildings
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Akçay, Yusuf Ali.; Edinçliler, Ayşe.
Soil reinforcement is used to improve the stiffness and strength of soil. The benefits of reinforcement inclusions within soil mass to increase the bearing capacity and reduce the settlement of soil foundation have been widely studied. The principle of geosynthetic reinforced soil method briefly is to deploy horizontal layers of closely spaced tensile inclusion in the fill material to achieve stability of a soil mass. This study aimed to determine the applicability and effectiveness of a proposed geogrid reinforcement system for low-rise and mid-rise buildings under earthquake loadings to mitigate earthquake effects. In order to observe the effectiveness of the proposed reinforcement system, a set of shaking table experiments were carried out with and without soil reinforcement. To determine structure and soil behavior together, an experimental set-up was desgined. The effects of the number of the story, the number of geogrids layers and ground motion characteristic were evaluated and the effects of all these parameters on system were investigated. There are many experimental studies showing that the ratio of geogrid length (L) to building foundation width (B) affects experimental results under static loads. In this study, the L/B ratio was taken as 2.3. This value is the highest possible L/B ratio due to limitations in the experimental setup. When the results of experiments are evaluated, it is clearly seen that proposed reinforcement system can reduce the horizontal accelerations, horizontal drifts in the soil, story displacement of the building. The seismic energy transmitted from ground to the structure without geogrid reinforcement system in the soil can be decreased through this system. Therefore, proposed geogrid reinforcement system can be used to improve the seismic resistance capacity of the structures against strong ground motions.
Experimental study on effects of geogrid reinforced zone on seismic performance of low-to-medium rise buildings
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2020., 2020.) Küçükakyüz, Okan.; Erdinçliler, Ayşe.
This study aims to investigate the effectiveness and reliability of geogrids as a soil reinforcing system. In order to prevent or minimize the earthquake impact on structures, this study focuses on reducing the effect of earthquake loads by creating the geogrid reinforced zones. This system is composed of various layers of geogrid configurations to be able to create a reinforced geogrid foundation under the structure. To present reliable results through observing the soil-structure interaction and structural behaviour and digital comparisons via data outputs; an experimental setup was established. With this purpose in mind, the seismic behavior of the two 1:10 scaled structure models without and with the different geogrid reinforcement configurations under different earthquake conditions were studied. A series of shaking table tests were performed to evaluate the seismic response of the building models depending on the selected performance criteria. The effects of geogrid reinforced zone which is dependent on the number of geogrid layers on the seismic behaviour of the low-rise and medium rise buildings were discussed with comparing test results of the unreinforced and reinforced cases. Comparison results of the tests revealed that the inclusion of the geogrid reinforcement to the sand can reduce earthquake impacts by decreasing the transmitted seismic energy from soil to structure via the interlocking mechanism between geogrid layers and soil. Significant improvements in reducing forces of strong ground motions are able to make geogrid reinforced soil systems an option to improve seismic performance of the structures.
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.
Influence of modeling parameters on seismic response of steel moment resisting frames
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2003., 2003.) Gündüz, Ahmet Suat.; Aydınoğlu, M. Nuray.
The purpose of this work is to identify the building response to variations in modeling parameters and assumptions for the steel mid-rise buildings. The behavior and response of 9-story building in Los Angeles are studied. The building that was designed according to the UBC 1994 provisions was used in the analysis. Different models for this structure were developed and analyzed dynamically. The models investigated involved the use of centerline dimensions of elements, or clear length dimensions (rigid zone effect), nonlinear springs for the beam connections, and nonlinear springs for the panel zones. Also, P-delta effects on the system response to the ground motions were investigated. Nonlinear time-history analysis was used to assess the performance of buildings subjected to strong earthquake ground motions. The global (roof) and story level displacement demands, story drift ratio demands, beam and panel zone plastic rotation demands, location of plastic rotations of the systems, and the story shears were obtained by subjecting the six models to set of 10 ground motions representative of a 10150 (10% probability of being exceeded in 50 years) hazard level. The results are compared to evaluate the influence of modeling assumptions on the nonlinear dynamic response of the structures. As a result it is concluded that, the effect of analytical modeling is intrinsic to understanding the response of the structure. The overall effect of the different models can result in significant changes in the demands. Moreover, structure P-delta effects are found to have a potentially severe influence on the response of steel moment resisting structures.

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