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ANSAL, Mustafa Atilla

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Mustafa Atilla

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Now showing 1 - 10 of 27
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    Eulogy to Professor Nicholas N. Ambraseys
    (Springer Science+Business Media, 2013-02) Ansal, Mustafa Atilla; Civil Engineering; ANSAL, Mustafa Atilla
    Sadly, at the final phase of all these preparations for Vol.11 N.1, our very dear and very distinguished Editorial Board Member Prof. Nicholas Ambraseys passed away on December 28, 2012 at the age of 83. Prof. Ambraseys played a very positive and crucial role in the initiation of the Bulletin of Earthquake Engineering ten years ago. He attended the EAEE Executive Committee Meeting held in Lisbon on September 16, 2000 and supported the publication of a new technical journal as the official journal of EAEE. As the Editorial Board of BEE, we believe it would be very appropriate to dedicate this issue to our great mentor, colleague and great researcher, Professor Nicholas Ambraseys. He recently submitted two manuscripts to be published in BEE. The first one “Assessment of the long-term seismicity of Athens from two classical columns” was published in the V.10 N.6 (2012). The second one “Ottoman archives and the assessment of the seismicity of Greece 1456–1833” is in the review stage.
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    Site characterization for site response analysis in performance based approach
    (Springer, 2022) Ansal, Mustafa Atilla; Tönük, G.; Civil Engineering; ANSAL, Mustafa Atilla
    The local seismic hazard analysis would yield probabilistic uniform hazard acceleration response spectrum on the engineering bedrock outcrop. Thus, site-specific response analyses need to produce a probabilistic uniform hazard acceleration response spectrum on the ground surface. A possible performance based approach for this purpose requires a probabilistic estimation of soil stratification and engineering properties of encountered soil layers in the soil profile. The major uncertainties in site-specific response analysis arise from the variabilities of (a) local seismic hazard assessment, (b) selection and scaling of the hazard compatible input earthquake time histories, (c) soil stratification and engineering properties of encountered soil and rock layers, and (d) method of site response analysis. Even though the uncertainties related to first two items have primary importance on the outcome of the site-specific response analyses, the discussion in this article focuses on the observed variability and level of uncertainty in site conditions, related to soil stratification, thickness and type of encountered soil layers and their engineering properties, depth of ground water table and bedrock and properties of the engineering bedrock. Thus, one option may be conducting site response analyses for large number of soil profiles produced by Monte Carlo simulations for the investigated site to assess probabilistic performance based design acceleration spectra and acceleration time histories calculated on the ground surface based on 1D, 2D, or 3D site response analysis with respect to different performance levels.
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    Editorial and welcome to a new ERA
    (Springer International Publishing, 2015-01) Ansal, Mustafa Atilla; Civil Engineering; ANSAL, Mustafa Atilla
    With this first issue of Volume 13 (2015), while we are celebrating our 12th anniversary, we will be implementing some major changes for BEE. We are going to start publishing on a monthly basis with 12 issues per year and introduce eight new Associate Editors. I would like to take this opportunity to welcome the eight Associate Editors who will be sharing the Editorial responsibilities.
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    Site response analysis in performance based approach
    (Elsevier, 2024-03) Ansal, Mustafa Atilla; Tönük, G.; Sadegzadeh, Shima; Civil Engineering; ANSAL, Mustafa Atilla
    A performance based approach for site response analysis requires a probabilistic approach accounting for the observed variability in soil stratification and engineering properties of the soil layers. The major variability in site-specific response analysis arises from the uncertainties induced by the (a) local seismic hazard assessment, (b) selection and scaling of the hazard compatible input earthquake time histories, (c) soil stratification and engineering properties of encountered soil and rock layers, and (d) method of site response analysis. Even though the uncertainties related to first item, local seismic hazard assessment, has primary importance on the outcome of the site-specific response analyses, the discussion in this article focuses on the possible uncertainties in selection and scaling of the hazard compatible input earthquake time histories, soil stratification, thickness, type and their engineering properties, depth of ground water table and bedrock and properties of the engineering bedrock. One alternative may be to conduct site response analyses for large number of soil profiles generated by Monte Carlo simulations using relatively large number of hazard compatible acceleration time histories to assess probabilistic performance based design acceleration spectra and acceleration time histories calculated on the ground surface with respect to different performance levels. A remaining issue may be considered as the variability induced by 1D, 2D, and 3D site response analysis.
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    Probabilistic seismic microzonation for ground shaking intensity, a case study in Türkiye
    (Springer, 2023-10) Tönük, G.; Ansal, Mustafa Atilla; Civil Engineering; ANSAL, Mustafa Atilla
    The purpose of seismic microzonation is to estimate earthquake characteristics on the ground surface based on a probabilistic approach to mitigate earthquake damage in the foreseeable future for the new buildings, as well as for the existing building stock. The probabilistic analysis and related results are very important from an engineering perspective since the nature of the problem can only be dealt with in a probabilistic manner. The uncertainties associated with these analyses may be large due to the uncertainties in source characteristics, soil profile, soil properties, and building inventory. At this stage, the probability distribution of the related earthquake parameters on the ground surface may be determined based on hazard-compatible input acceleration-time histories, site profiles, and dynamic soil properties. One option, the variability in earthquake source and path effects may be considered using a large number of acceleration records compatible with the site-dependent earthquake hazard. Likewise, large numbers of soil profiles may be used to account for the site-condition variability. The seismic microzonation methodology is proposed based on the probabilistic assessment of these factors involved in site response analysis. The second important issue in seismic microzonation procedure is the selection of microzonation parameters. The purpose being mitigation of structural damage, it is possible to adopt earthquake parameters like cumulative average velocity (CAV) or Housner intensity (HI) that was observed to have better correlation with building damage after earthquakes. A seismic microzonation procedure will be developed with respect to ground shaking intensity considering probabilistic values of the cumulative average velocity (CAV) or Housner intensity (HI).
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    A simplified approach for site-specific design spectrum
    (Springer, 2018) Ansal, Mustafa Atilla; Tönük, G.; Kurtuluş, Aslı; Civil Engineering; Rupakhety, R.; Ólafsson, S.; ANSAL, Mustafa Atilla; KURTULUŞ, Asli
    The design acceleration spectrum requires site investigations and site-response analyses in accordance with the local seismic hazard. The variability in earthquake source and path effects may be considered using a large number of acceleration records compatible with the earthquake hazard. An important step is the selection and scaling of input acceleration records. Likewise, a large number of soil profiles need to be considered to account for the variability of site conditions. One option is to use Monte Carlo simulations with respect to layer thickness and shear wave velocity profiles to account for the variability of the site factors. The local seismic hazard analysis yields a uniform hazard acceleration spectrum on the bedrock outcrop. Site-specific response analyses also need to produce a uniform hazard acceleration spectrum on the ground surface. A simplified approach is proposed to define acceleration design spectrum on the ground surface that may be considered a uniform hazard spectrum.
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    Observations from geotechnical arrays in Istanbul
    (Springer, 2015-04-16) Kurtuluş, Aslı; Ansal, Mustafa Atilla; Tönük, G.; Çetiner, B.; Civil Engineering; KURTULUŞ, Asli; ANSAL, Mustafa Atilla
    Few small earthquakes with local magnitude slightly larger than ML = 4 were recorded by geotechnical downhole arrays that have been recently deployed in the west side of Istanbul. Same events were also recorded by Istanbul Rapid Response Network (IRRN) which comprises of 55 surface strong motion stations in the European side of Istanbul. The strongest one of these earthquakes took place on 12/3/2008 in Çınarcık with local magnitude of ML = 4.8. Even though the observed PGAs were not exceeding 0.01 g, an effort is made to model the recorded response at the downhole array sites as well as the at the IRRN stations using the acceleration records obtained by the deepest sensors, i.e. on the engineering bedrock, at the downhole array sites as input bedrock motions. 1D equivalent linear site response analysis that is generally adopted for site-specific response analysis is used for modelling. Observations from the recorded response and results from 1D modelling of ground response have yielded in general good agreement between the observed and recorded soil response at the station sites.
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    Analysis of offshore wind turbine by considering soil-pile-structure interaction: effects of foundation and sea-wave properties
    (Taylor & Francis, 2022) Fard, Maryam Massah; Erken, A.; Erkmen, Bülent; Ansal, Mustafa Atilla; Civil Engineering; FARD, Maryam Massah; ERKMEN, Bülent; ANSAL, Mustafa Atilla
    Prediction of the dynamic performance of an offshore wind turbine (OWT) requires consideration of many different design parameters. Besides the superstructure, the OWT foundation also plays an important role both functionally and financially in the design. In this study, numerical dynamic analyses of an offshore wind turbine with a monopile foundation are performed under wave loading that may lead to soil liquefaction around the pile due to cyclic stresses induced by the pile displacements using the open-source program, OpenSees. Effects of foundation properties such as monopile diameter, pile embedment depth, and sea-wave characteristics such as its period, sea-water depth, duration, and level of the loading on the dynamic performance of the system are investigated. The results in terms of deformations, excess pore water pressure, and inertial forces are presented and discussed. The findings are considered as valuable guidance on the estimation of the dynamic performance and liquefaction susceptibility of the offshore wind turbine foundations under cyclic sea-wave loads.
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    Preface to the second decade
    (Springer Science+Business Media, 2013-02) Ansal, Mustafa Atilla; Civil Engineering; ANSAL, Mustafa Atilla
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    Implications of site specific response analysis
    (Springer, 2018) Ansal, Mustafa Atilla; Tönük, G.; Kurtuluş, Aslı; Civil Engineering; Pitilakis, K.; ANSAL, Mustafa Atilla; KURTULUŞ, Asli
    Definition of design earthquake characteristics, more specifically uniform hazard acceleration response spectrum, on the ground surface is the primary component for performance based design of structures and assessment of seismic vulnerabilities in urban environments. The adopted approach for this purpose requires a probabilistic local seismic hazard assessment, definition of representative site profiles down to the engineering bedrock, and 1D or 2D equivalent or nonlinear, total or effective stress site response analyses depending on the complexity and importance of the structures to be built. Thus, a site-specific response analysis starts with the probabilistic estimation of regional seismicity and earthquake source characteristics, soil stratification, engineering properties of encountered soil layers in the soil profile. The local seismic hazard analysis would yield probabilistic uniform hazard acceleration response spectrum on the bedrock outcrop. Thus, site specific response analyses also need to produce a probabilistic uniform hazard acceleration response spectrum on the ground surface. A general review will be presented based on the previous studies conducted by the author and his co-workers in comparison to major observations and methodologies to demonstrate the implications of site-specific response analysis.