Doğrusal olmayan tek serbestlik dereceli sistem davranışının kullanılabilir periyot aralıklarının yüksek geçirimli filtrelemeye dayalı belirlenmesine yönelik ampirik ilişkisi.

High-pass filtering that is one of the most efficient methods in removing long-period noise of accelerograms is investigated for its effect on nonlinear oscillator deformation response. Within this context, uncertainty in filter cut-off periods that would significantly modify the low-frequency content of accelerograms come into prominence for obtaining reliable long-period displacement response. Analog and digital ground-motion records from recently compiled Turkish strong-motion database are used and these records are high-pass filtered with a consistent methodology by randomly generated filter cut-offs that represent different filter cut-off decisions of the analysts. The uncertainty in inelastic spectral and residual displacements (SDIE and SDR, respectively) due to variations in filter cut-offs is examined to derive the usable period ranges where the effect of high-pass filtering is tolerable. Non-degrading, stiffness degrading and stiffness and strength degrading oscillator behavior are considered in these analyses. The level of nonlinear behavior in single degree of freedom (SDOF) response is described by varying the yield strength (R, normalized yield strength) and displacement ductility (µ) levels. The usable period ranges that depend on magnitude, recording quality, level of inelasticity and level of degradation are determined for SDIE through robust probabilistic methodologies.M.S. - Master of Scienc

Kesirsel Mertebeli Şiddet Ölçülerinin Olasılıksal Sismik Talep Modellerinde Kullanımının Tek Serbestlik Dereceli Sistemlerle Değerlendirilmesi

Bu çalışma kapsamında, yapıların sismik risk değerlendirmelerinin önemli  bileşenlerinden biri olan olasılıksal sismik talep modellerinde (PSDM) kesirsel mertebeli şiddet ölçülerinin kullanılabilirliği araştırılmıştır. Bu amaçla, tek serbestlik dereceli (SDF) sistemlerin farklı seviyelerdeki doğrusal olmayan deplasman talepleri kullanılmıştır. Analizlerde, rijitlik azalımsız elastoplastik (bilineer) ve rijitlik azalımlı Clough davranım modelleri dikkate alınmıştır. SDF sistemlerin doğrusal olmayan davranış düzeyleri, normalize edilmiş akma kapasitesi (R) ve süneklik (µ) değerlerinin farklı seviyeleri ile hesaba katılmıştır. Genel değerlendirmeler, kesirsel mertebeli şiddet ölçüleri olarak maksimum kesirsel yer tepkileri ve T = 0.2 s ve 1.0 s için kesirsel sönümlü spektral ivme değerlerine karşılık seçilen konvansiyonel şiddet ölçülerinden maksimum yer ivmesi (PGA), yer hızı (PGV) ve yer deplasmanı (PGD) ve T = 0.2 s ve 1.0 s için spektral ivmeler kullanılarak yapılmıştır. Bu parametrelerle oluşturulan PSDM’lerden elde edilen belirleme katsayısı (R2) ve model belirsizliğinin yanısıra hesaplanan korelasyon katsayılarının da yardımıyla kesirsel mertebeli şiddet ölçülerinin risk çalışmaları için uygunluğu değerlendirilmiştir. Elde edilen bulgular, maksimum kesirsel yer tepkisi kullanılarak oluşturulan PSDM’lerin konvansiyonel şiddet ölçülerine göre daha düşük belirsizlik ve daha yüksek R2 ve korelasyon katsayısına sahip olduğunu göstermiştir. Ayrıca en efektif kesirsel  mertebe değerlerinin de periyoda bağlı olarak değiştiği elde edilmiştir

Kesirsel Mertebeli Şiddet Ölçülerinin Olasılıksal Sismik Talep Modellerinde Kullanımının Tek Serbestlik Dereceli Sistemlerle Değerlendirilmesi

Bu çalışma kapsamında, yapıların sismik risk değerlendirmelerinin önemli  bileşenlerinden biri olan olasılıksal sismik talep modellerinde (PSDM) kesirsel mertebeli şiddet ölçülerinin kullanılabilirliği araştırılmıştır. Bu amaçla, tek serbestlik dereceli (SDF) sistemlerin farklı seviyelerdeki doğrusal olmayan deplasman talepleri kullanılmıştır. Analizlerde, rijitlik azalımsız elastoplastik (bilineer) ve rijitlik azalımlı Clough davranım modelleri dikkate alınmıştır. SDF sistemlerin doğrusal olmayan davranış düzeyleri, normalize edilmiş akma kapasitesi (R) ve süneklik (µ) değerlerinin farklı seviyeleri ile hesaba katılmıştır. Genel değerlendirmeler, kesirsel mertebeli şiddet ölçüleri olarak maksimum kesirsel yer tepkileri ve T = 0.2 s ve 1.0 s için kesirsel sönümlü spektral ivme değerlerine karşılık seçilen konvansiyonel şiddet ölçülerinden maksimum yer ivmesi (PGA), yer hızı (PGV) ve yer deplasmanı (PGD) ve T = 0.2 s ve 1.0 s için spektral ivmeler kullanılarak yapılmıştır. Bu parametrelerle oluşturulan PSDM’lerden elde edilen belirleme katsayısı (R2) ve model belirsizliğinin yanısıra hesaplanan korelasyon katsayılarının da yardımıyla kesirsel mertebeli şiddet ölçülerinin risk çalışmaları için uygunluğu değerlendirilmiştir. Elde edilen bulgular, maksimum kesirsel yer tepkisi kullanılarak oluşturulan PSDM’lerin konvansiyonel şiddet ölçülerine göre daha düşük belirsizlik ve daha yüksek R2 ve korelasyon katsayısına sahip olduğunu göstermiştir. Ayrıca en efektif kesirsel  mertebe değerlerinin de periyoda bağlı olarak değiştiği elde edilmiştir

Olasılıksal sismik tehlike analizleri için yer hareketi tahmin denklemlerinin sıralanmasında ve seçilmesinde kullanılacak pratik araçlar ve bölgesel bir yer hareketi tahmin denkleminin geliştirilmesi.

This study starts summarizing the progresses in ground-motion databases and ground-motion models in pan-European region and consequent seismic hazard comparisons conducted for individual local and global predictive models. Then, the study presents the compilation of the Middle East region and Turkish ground-motion databases with principle seismological features to be mainly used in predictive model selection process in these regions. In the following step, using a high standard subset of the Middle East ground-motion database, a ground-motion prediction equation (GMPE) is developed for Turkey and Iran to investigate the possible regional effects on ground-motion amplitudes in shallow active crustal earthquakes. Next part introduces a method for ranking and selection of GMPEs based on Euclidean distance concept. The proposed method is capable of determining the proper set of predictive models for regional or site-specific probabilistic seismic hazard assessment (PSHA) under a given set of observed ground-motion data. To this end, an alternative method for establishing ground-motion logic-tree framework for PSHA is represented in the following part of the study. The proposed method evaluates the effects of the predictive models and corresponding branch weights selected for logic-tree framework to properly capture the epistemic uncertainty in seismic hazard analysis. As a final point, a ground-motion logic-tree framework combining the functionalities of data-driven GMPE testing methods and logic-tree based sensitivity approach are proposed for shallow active crustal regions in EMME (Earthquake Model of the Middle East Region) project.Ph.D. - Doctoral Progra

PERSPECTIVES ON EUROPEAN EARTHQUAKE ENGINEERING AND SEISMOLOGY, VOL 2

This paper summarizes the evolution of major strong-motion databases and ground-motion prediction equations (GMPEs) for shallow active crustal regions (SACRs) in Europe and surrounding regions. It concludes with some case studies to show the sensitivity of hazard results at different seismicity levels and exceedance rates for local (developed from country-specific databases) and global (based on databases of multiple countries) GMPEs of the same region. The case studies are enriched by considering other global GMPEs of SACRs that are recently developed in the USA. The hazard estimates computed from local and global GMPEs from the broader Europe as well as those obtained from global GMPEs developed in the US differ. These differences are generally significant and their variation depends on the annual exceedance rate and seismicity. Current efforts to improve the accelerometric data archives in the broader Europe as well as more refined GMPEs that will be developed from these databases would help the researchers to understand the above mentioned differences in seismic hazard

The Effects of Implementing Different Ground-motionLogic-tree Frameworks on Seismic Risk Assessment

This study investigates the link between probabilistic seismic hazard assessment and corresponding loss estimations by using different ground-motion logic-tree frameworks from reliable large scale seismic hazard projects as well as the logic-tree framework established in this study. The predictive models selected for these logic trees are expected to represent the center, body and range of ground-motion intensity measure estimates. Regarding with the hazard component of risk assessment, the ground motion intensities obtained by alternative logic-tree frameworks showed considerable dispersion. To scrutinize the effect of this dispersion on seismic risk and loss assessment, fragility curves derived for low and mid-rise reinforced concrete and masonry structures in İstanbul are used. The comparisons of loss estimations indicate the importance of the uncertainty in ground motion intensity calculations and the decision making process of hazard calculation for seismic risk and loss estimations studies

The role of multidetector computed tomography in evaluation of small bowel obstructions

Objective: The purpose of the study was to evaluate therole and additional diagnostic contribution of multi-detectorcomputed tomography (MDCT) in patients with acuteabdominal pain caused by small bowel obstruction.Materials and methods: A total of 48 patients who admittedto our hospital with acute abdominal pain and underwentMDCT on suspicion of intestinal obstruction and hadabdominal surgery between January 2012 and October2012 were included to our study. MDCT images were interpretedby two experienced radiologist retrospectively.All clinical data and surgery notes also were evaluated.Patients had surgery due to penetrating or blunt abdominalinjury were excluded.Results: Of these 48 patients, 26 (54.1%) were male and22 (45.9%) were female. Patients’ ages ranged 25 to 71and mean age was 52±5.4 years. The causes of intestinalobstruction of patients were adhesions for 12 (46.1%) patients,tumors for 7 (26.9%) patients, external hernias for5 (19.2%) patients, internal hernia for 1 (3.9%) patient andintussusception for 1 (3.9%) patient. A total concordancebetween the MDCT findings and definitive diagnosis wasfound in 26 of 23 cases and the sensitivity and specifityof MDCT in the diagnosis of small bowel obstruction werefound to be 88.5% and 90%, respectively.Conclusion: MDCT is a fast, effective and reliable imagingmethod for preoperative diagnosing small bowel obstructioncauses acute abdominal pain with the advantagesof MDCT such as multi-planar and three-dimensionalreformatted imaging.Key words: Acute abdominal pain, multi-detector computed tomography, small bowel obstructio

The Samos Island (Aegean Sea) M7.0 earthquake: analysis and engineering implications of strong motion data

© 2021, The Author(s), under exclusive licence to Springer Nature B.V.We present a dataset of 77 strong ground motion records within 200 km epicentral distance from the 30 October 2020, M7.0 Samos Island (Aegean Sea) earthquake, which affected Greece and Turkey. Accelerograms from National Networks of both countries have been merged into a single dataset, including metadata that have been uniformly derived using a common preliminary source model. Initial findings from the analysis and comparative examination of acceleration time histories, Fourier amplitude spectra and 5%-damped response spectra are discussed along with significant source, propagation path and site effects. The long-period amplifications observed in most records in Izmir bay triggered failures and severe damages in weak structures. Yet, the spectral accelerations are observed to lie below the current and previous design spectra corresponding to the damaged regions. Peak ground motions are used to construct a purely instrumental-based macroseismic intensity map, which is capable of reflecting the actual earthquake damage caused by this considerably large event. Finally, peak ground motions are compared to various ground motion models (GMMs) and deviations are highlighted. Our overall preliminary analysis reveals a strong energy signature of the Samos earthquake in the period range 0.5–1.5 s at many sites, both on rock and soil, whereas records in the heavily hit Izmir city, at an epicentral distance circa 70 km, provide strong indication for additional amplification due to basin effects. At relatively large distance from the earthquake source (> 120 km), several recorded amplitudes are significantly lower than those predicted by many GMMs, implying that further studies are necessary toward the improvement of regional attenuation models