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  Subjects -> EARTH SCIENCES (Total: 589 journals)
    - EARTH SCIENCES (436 journals)
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EARTH SCIENCES (436 journals)            First | 1 2 3 4 5     

Mountain Research and Development     Open Access   (Followers: 3)
Natural Hazards     Hybrid Journal   (Followers: 203)
Natural Hazards and Earth System Sciences (NHESS)     Open Access   (Followers: 7)
Natural Hazards Review     Full-text available via subscription   (Followers: 7)
Natural Resources Research     Hybrid Journal   (Followers: 4)
Nature Geoscience     Full-text available via subscription   (Followers: 189)
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen     Full-text available via subscription   (Followers: 3)
Neues Jahrbuch für Mineralogie - Abhandlungen     Full-text available via subscription   (Followers: 3)
New Journal of Physics     Open Access   (Followers: 7)
Newsletters on Stratigraphy     Full-text available via subscription   (Followers: 6)
Nonlinear Processes in Geophysics (NPG)     Open Access   (Followers: 3)
Ocean & Coastal Management     Hybrid Journal   (Followers: 160)
Ocean Development & International Law     Hybrid Journal   (Followers: 11)
Ocean Dynamics     Hybrid Journal   (Followers: 5)
Ocean Engineering     Hybrid Journal   (Followers: 3)
Ocean Modelling     Hybrid Journal   (Followers: 4)
Ocean Science (OS)     Open Access   (Followers: 6)
Ocean Science Discussions (OSD)     Open Access   (Followers: 5)
Ocean Science Journal     Hybrid Journal   (Followers: 3)
Open Journal of Soil Science     Open Access   (Followers: 4)
Ore Geology Reviews     Hybrid Journal   (Followers: 3)
Organic Geochemistry     Hybrid Journal   (Followers: 7)
Osterreichische Wasser- und Abfallwirtschaft     Hybrid Journal  
Paläontologische Zeitschrift     Hybrid Journal   (Followers: 3)
Papers on Global Change IGBP     Open Access   (Followers: 1)
Permafrost and Periglacial Processes     Hybrid Journal   (Followers: 3)
Pesquisas em Geociências     Open Access   (Followers: 1)
Petroleum Geoscience     Hybrid Journal   (Followers: 5)
Petrology     Hybrid Journal   (Followers: 6)
Photogrammetrie - Fernerkundung - Geoinformation     Full-text available via subscription  
Physical Geography     Hybrid Journal   (Followers: 5)
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 7)
Physics of Life Reviews     Hybrid Journal   (Followers: 1)
Physics of Plasmas     Hybrid Journal   (Followers: 6)
Physics of the Earth and Planetary Interiors     Hybrid Journal   (Followers: 10)
Physics of the Solid State     Hybrid Journal   (Followers: 3)
Physics of Wave Phenomena     Hybrid Journal   (Followers: 1)
Physics World     Full-text available via subscription   (Followers: 3)
Physik in unserer Zeit     Hybrid Journal  
Pirineos     Open Access  
Planet     Open Access   (Followers: 1)
Plasma Physics and Controlled Fusion     Hybrid Journal   (Followers: 2)
Plasma Physics Reports     Hybrid Journal   (Followers: 2)
Polish Polar Research     Open Access   (Followers: 4)
Positioning     Open Access   (Followers: 1)
Pramana     Open Access   (Followers: 9)
Precambrian Research     Hybrid Journal   (Followers: 5)
Preview     Hybrid Journal  
Procedia Earth and Planetary Science     Open Access   (Followers: 4)
Proceedings in Marine Science     Full-text available via subscription   (Followers: 3)
Proceedings of the Geologists' Association     Full-text available via subscription   (Followers: 3)
Proceedings of the Linnean Society of New South Wales     Full-text available via subscription   (Followers: 1)
Proceedings of the Yorkshire Geological Society     Hybrid Journal  
Pure and Applied Geophysics     Hybrid Journal   (Followers: 8)
Quarterly Journal of Engineering Geology and Hydrogeology     Hybrid Journal   (Followers: 5)
Quaternary Australasia     Full-text available via subscription  
Quaternary Geochronology     Hybrid Journal   (Followers: 4)
Quaternary International     Hybrid Journal   (Followers: 10)
Quaternary Research     Full-text available via subscription   (Followers: 15)
Quaternary Science Reviews     Hybrid Journal   (Followers: 10)
Radiocarbon     Open Access   (Followers: 2)
Raumforschung und Raumordnung     Hybrid Journal  
Remote Sensing     Open Access   (Followers: 13)
Remote Sensing Letters     Hybrid Journal   (Followers: 9)
Remote Sensing Science     Open Access   (Followers: 3)
Rendiconti Lincei     Hybrid Journal  
Reports on Mathematical Physics     Full-text available via subscription  
Reports on Progress in Physics     Full-text available via subscription   (Followers: 2)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription  
Resource Geology     Hybrid Journal   (Followers: 4)
Reviews in Mineralogy and Geochemistry     Full-text available via subscription  
Reviews of Modern Physics     Full-text available via subscription   (Followers: 16)
Revista Boletín Ciencias de la Tierra     Open Access   (Followers: 2)
Revista Brasileira de Geofísica     Open Access   (Followers: 4)
Revista de Ingenieria Sismica     Open Access  
Revista de la Sociedad Entomologica Argentina     Open Access   (Followers: 2)
Revista de Topografía Azimut     Open Access   (Followers: 1)
Revista Eletrônica Científica Inovação e Tecnologia     Open Access  
Revista Geológica de Chile     Open Access   (Followers: 2)
River Systems     Full-text available via subscription   (Followers: 3)
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 5)
Rocks & Minerals     Hybrid Journal   (Followers: 2)
Russian Geology and Geophysics     Hybrid Journal   (Followers: 2)
Russian Journal of Mathematical Physics     Hybrid Journal  
Russian Journal of Pacific Geology     Hybrid Journal   (Followers: 1)
Russian Physics Journal     Hybrid Journal  
Science China Earth Sciences     Hybrid Journal   (Followers: 2)
Science News     Hybrid Journal   (Followers: 15)
Scientific Annals of Stefan cel Mare University of Suceava. Geography Series     Open Access  
Scientific Journal of Earth Science     Open Access  
Scientific Reports     Open Access   (Followers: 10)
Scottish Journal of Geology     Hybrid Journal   (Followers: 5)
Sedimentary Basins of the World     Full-text available via subscription   (Followers: 2)
Sedimentary Geology     Hybrid Journal   (Followers: 11)
Sedimentology     Hybrid Journal   (Followers: 10)
Seismic Instruments     Hybrid Journal   (Followers: 1)
Seismological Research Letters     Full-text available via subscription   (Followers: 2)
Soil Dynamics and Earthquake Engineering     Hybrid Journal   (Followers: 7)
Solid Earth     Open Access   (Followers: 3)
Solid Earth Discussions     Open Access   (Followers: 1)

  First | 1 2 3 4 5     

Journal Cover Soil Dynamics and Earthquake Engineering
   Journal TOC RSS feeds Export to Zotero [9 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0267-7261
     Published by Elsevier Homepage  [2563 journals]   [SJR: 1.116]   [H-I: 39]
  • Evaluation of state indices in predicting the cyclic and monotonic
           strength of sands with different fines contents
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Abbas Qadimi , Amirabbas Mohammadi
      State parameter, ψ, has been widely used to combine the influence of void ratio, e, and stress level, p′, on the soils behavior. Stress ratio, R s, and modified state parameter, ψ m, have also been proposed for the same purpose. This paper aims to evaluate and compare the different state indices in combining the effect of fines content, density and stress level for five different types of sands, by processing a large number of previously published experimental data. The use of the recently established concept of equivalent interparticle void ratio, e ⁎, in definition of the state indices is also evaluated. The results indicate that the influence of fines presence, in addition to the e and p′, on the behavior is favorably reflected by the state indices. Unique correlations were derived between the cyclic or monotonic strength and each of the state indices, independent of the fines content. The correlations, for all the different types of soils, fell into limited types of common formulations. ψ and R s worked generally better than ψ m, whether defined in terms of e or e ⁎ . The extension of straight part of critical state line was found to be an appropriate reference line for calculating R s used in conjunction with e or e ⁎.


      PubDate: 2014-09-08T01:09:13Z
       
  • Variation of earthquake ground motions within a very small distance
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Yoshiya Hata , Atsushi Nozu , Koji Ichii
      At present, dense strong motion observation networks have been established in Japan. One of the important findings based on these networks is that strong ground motions are quite site-dependent. Characteristics of observed ground motions at nearby stations can exhibit a significant variation, even when the stations are within several hundreds of meters. These observations raise one important question; if characteristics of strong ground motions exhibit large variations even for smaller regions, we should be concerned about the application of observed or predicted ground motions for the assessment of structures. In particular, if ground-motion parameters such as PGA, PGV, Spectral Intensity, etc., exhibit large variations for smaller regions, their use for the seismic design and practice will be subject to restriction. In other words, the evaluation of variation of these parameters is an important issue. From such a point of view, the authors investigated the variation of observed ground motions within a very small distance in this study. First of all, fifteen couples of adjacent strong motion stations in Japan, where the distance is within 100m, were listed up based on our field reconnaissance. Then, microtremor measurements were carried out at each of the station pairs. Next, variation of recorded earthquake ground motions for the station pairs was examined based on various ground motion parameters and response spectra. Moreover, we investigated the key factor which is affecting the variation of observed ground motions.


      PubDate: 2014-09-08T01:09:13Z
       
  • Detection thresholds in structural health monitoring
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): M.D. Trifunac , M. Ebrahimian
      Most health-monitoring methods for analysis of full-scale structures detect changes in the soil-system response by comparison of the identified response parameters “before” and “after” large excitations. However, because the deformations of the foundation soil, which are almost always present, are nonlinear, and because permanent deformations and changes in the soil depend differently on the excitation histories of different sites, it is difficult at best to (1) make use of classical concepts, which are based on signal-to-noise ratio, and (2) the vibrational description of the response in terms of transfer functions. This situation then necessitates a selection of methods and metrics that detect changes in the system parameters that (1) can be evaluated in almost real-time conditions, and (2) are as insensitive as possible to the contributions to the response of the soil–structure interaction. This, in turn, requires case-by-case, specific, and complex methods of analysis, which can only occasionally be generalized to other buildings and which can also be quite different from one event to the next. In this paper, we present examples of what has been done thus far to avoid the associated complexities for a group of full-scale structures, two of which experienced damaging response during earthquake shaking. In the examples presented, we emphasize those features of the analyses that are related to detection thresholds and to the time- and case-dependent amplitudes of the detection “noise”.


      PubDate: 2014-09-02T23:55:12Z
       
  • Idealisation of soil–structure system to determine inelastic seismic
           response of mid-rise building frames
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Hamid Reza Tabatabaiefar , Behzad Fatahi
      In this study, a novel and enhanced soil–structure model is developed adopting the direct analysis method using FLAC 2D software to simulate the complex dynamic soil–structure interaction and treat the behaviour of both soil and structure with equal rigour simultaneously. To have a better judgment on the inelastic structural response, three types of mid-rise moment resisting building frames, including 5, 10, and 15 storey buildings are selected in conjunction with three soil types with the shear wave velocities less than 600m/s, representing soil classes Ce, De and Ee, according to Australian Standards. The above mentioned frames have been analysed under two different boundary conditions: (i) fixed-base (no soil–structure interaction) and (ii) flexible-base (considering soil–structure interaction). The results of the analyses in terms of structural displacements and drifts for the above mentioned boundary conditions have been compared and discussed. It is concluded that considering dynamic soil–structure interaction effects in seismic design of moment resisting building frames resting on soil classes De and Ee is essential.


      PubDate: 2014-09-02T23:55:12Z
       
  • Wave-induced dynamic response of saturated multi-layer porous media:
           Analytical solutions and validity regions of various formulations in
           non-dimensional parametric space
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Mehmet Barış Can Ülker
      In this paper, dynamic response of saturated-layered porous media under harmonic waves is evaluated through a semi-analytical solution. The coupled differential equations governing the dynamics of saturated or nearly saturated porous media such as soils containing all the inertial terms of solid and fluid phases are presented for a multi-layer system. Possible simplifications of the equations which are called formulations are introduced based upon the presence of inertial terms associated with the phases. The semi-analytical solutions to the response of multiple layers for all the formulations are presented in terms of pore water pressure and stress variations considering a set of non-dimensional parameters and their respective ratios. Validity of the formulations is presented in a non-dimensional parametric space. The maximum discrepancies in the pore pressure response of the formulations leading to validity regions are illustrated for typical dynamic problems. Subsequently, the effects of layering and drainage conditions on these regions are also presented. The proposed semi-analytical solution may be served as a benchmark one for validating the coupled numerical solutions, which can be used to deal with real scientific and geo-engineering problems in the emerging field of computational geomechanics.


      PubDate: 2014-09-02T23:55:12Z
       
  • Full-scale model testing on a ballastless high-speed railway under
           simulated train moving loads
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Xuecheng Bian , Hongguang Jiang , Chong Cheng , Yunmin Chen , Renpeng Chen , Jianqun Jiang
      Model testing in laboratory, as an effective alternative to field measurement, provides valuable data to understand railway׳s dynamic behaviors under train moving loads. This paper presents comprehensive experimental results on track vibration and soil response of a ballastless high-speed railway from a full-scale model testing with simulated train moving loads at various speeds. A portion of a realistic ballastless railway comprising slab track, roadbed, subgrade, and subsoil was constructed in a larger steel box. A computer-controlled sequential loading system was developed to generate equivalent vertical loadings at the track structure for simulating the dynamic excitations due to train׳s movements. Comparisons with the field measurements show that the proposed model testing can accurately reproduce dynamic behaviors of the track structure and underlying soils under train moving loads. The attenuation characteristics of dynamic soil stresses in a ballastless slab track is found to have distinct differences from that in a ballasted track. The model testing results provide better understanding of the influence of dynamic soil–structure interaction and train speed on the response of track structure and soils.


      PubDate: 2014-09-02T23:55:12Z
       
  • Damage scenarios for RC buildings during the 2012 Emilia (Italy)
           earthquake
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Gerardo M. Verderame , Paolo Ricci , Flavia De Luca , Carlo Del Gaudio , Maria Teresa De Risi
      The main features of the Reinforced Concrete (RC) building stock that was struck by the Emilia 2012 earthquake and damage observed after the event are analyzed. Building stock characteristics and historical seismic classification are employed for the definition of two benchmark structures, representative of the whole building stock. Seismic capacity of the two structures, at different damage states, is assessed through static push-over analyses, within the N2 spectral assessment framework. Infill panels׳ contribution in terms of strength and stiffness is explicitly taken into account in the analytical model. Damage States are defined according to a mechanical interpretation of EMS-98 scale. Fragility functions at each Damage State are obtained through the application of a Response Surface Method. Finally large-scale damage scenarios are obtained crossing the geo-referenced census data regarding the characteristics of the Emilia RC building stock and starting from the seismic input provided by the shake map of the event. The scenarios seem to be in reasonable agreement with the observed damage.


      PubDate: 2014-09-02T23:55:12Z
       
  • Impact and cyclic shaking on loose sand properties in laminar box using
           gap sensors
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Ata Aghaei Araei , Ikuo Towhata
      This paper focuses on using high-frequency GAP-SENSORs (GSs), accelerometers, and load cells in a laminar shear box (LSB) filled with loose Toyoura sand to understand the effects of impact loads and cyclic shaking at 1-G on soil properties. The shear wave velocity at small strain (V s ) was calculated directly from first arrival reference using displacement time-history of two GSs under impact loading. Moreover, from first peak using the reduced deformation amplitude technique, damping ratio was calculated. In addition, shaking table tests were performed under harmonic loading with amplitude of acceleration inside the model ground varying from 0.02g to 1g. The frequencies of excitation varied from 1Hz to 10Hz. GSs and inside accelerometers were used to directly measure the outside lateral deformation and shear stress at different elevations of LSB, respectively. Results show that the shear modulus (G) and the damping ratio (D) behavior of model sand are generally consistent with the behavior presented by similar tests using only accelerometers. In addition, damping ratio increases as frequency loading increases. Characteristic changes in two shear stress components in shaking loading conditions were also investigated using high precision inside load cells.


      PubDate: 2014-09-02T23:55:12Z
       
  • Approximate soil–structure interaction analysis by a perturbation
           approach: The case of soft soils
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Armando Lanzi , J. Enrique Luco
      An approximate solution of the classical eigenvalue problem governing the vibrations of a relatively stiff structure on a soft elastic soil is derived through the application of a perturbation analysis. The full solution is obtained as the sum of the solution for an unconstrained elastic structure and small perturbing terms related to the ratio of the stiffness of the soil to that of the superstructure. The procedure leads to approximate analytical expressions for the system frequencies, modal damping ratios and participation factors for all system modes that generalize those presented earlier for the case of stiff soils. The resulting approximate expressions for the system modal properties are validated by comparison with the corresponding quantities obtained by numerical solution of the eigenvalue problem for a nine-story building. The accuracy of the proposed approach and of the classical normal mode approach is assessed through comparison with the exact frequency response of the test structure.


      PubDate: 2014-09-02T23:55:12Z
       
  • A GIS-based seismic hazard, building vulnerability and human loss
           assessment for the earthquake scenario in Tabriz
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Sadra Karimzadeh , Masakatsu Miyajima , Reza Hassanzadeh , Reza Amiraslanzadeh , Batoul Kamel
      A GIS-oriented procedure that may partially illuminate the consequences of a possible earthquake is presented in two main steps (seismic microzonation and vulnerability steps) along with its application in Tabriz (a city in NW Iran). First, the detailed geological, geodetical, geotechnical and geophysical parameters of the region are combined using an Analytic Hierarchy Process (AHP) and a deterministic near-field earthquake of magnitude 7 in the North Tabriz Fault is simulated. This simulation provides differing intensities of ground shaking in the different districts of Tabriz. Second, the vulnerability of buildings, human losses and basic resources for survivors is estimated in district two of the city based on damage functions and relational analyses. The results demonstrate that 69.5% of existing buildings are completely destroyed, and the rate of fatalities is approximately 33% after a nighttime scenario. Finally, the same procedure was applied to an actual earthquake (first event on the 11th of August, 2012 of the Ahar twin earthquakes) to validate the presented model based on two aspects: (1) building damages and (2) seismic intensity.


      PubDate: 2014-08-16T22:30:50Z
       
  • Nonlinear dynamic analysis of base isolated cable-stayed bridge under
           earthquake excitations
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Barbaros Atmaca , Muhammet Yurdakul , Şevket Ateş
      In this paper, it is aimed to determine the earthquake effects on cable-stayed bridge isolated by single concave friction pendulum bearings (SCFP). In this context, Manavgat cable-stayed bridge is selected as a numerical application. The selected bridge has 202m composite deck and 42m steel tower. 3D finite element models (FEM) of the base isolated and non-isolated bridge are modeled by using SAP2000. Three different earthquakes which are 11 December 1999 Düzce, 23 November 2011 Van and 13 March 1992 Erzincan earthquakes are subjected to the 3D FEM models in order to determine the seismic behavior of the bridges. BOL-090 and BOL-000; ERCIS-EW and ERCIS-NS; ERZ-NS and ERZ-EW components of ground motions obtained from PEER and AFAD are applied to the bridges at the longitudinal and transverse directions, respectively. Nonlinear time history analysis is executed to determine the dynamic responses of the bridge. Comparison of dynamic behavior of isolated and non-isolated bridge with and without the SCFP bearings under three different earthquake motions has been conducted. The results obtained from analyses of 3D FEM of the bridge are presented by graphics and tables in detail. It is seen that using of isolation system reduces the destructive effects of earthquakes on the bridge.


      PubDate: 2014-08-16T22:30:50Z
       
  • Selection of spectrum- and seismo-compatible accelerograms for the Tuscany
           region in Central Italy
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Elisa Zuccolo , Mirko Corigliano , Carlo G. Lai
      This article illustrates the results of a study aimed at developing a methodology for the automatic identification of the seismic input at outcropping rock sites and flat topographic conditions necessary to carry out non-linear dynamic analysis of structures and geotechnical systems. The seismic input is provided in terms of a set of 7 natural accelerograms recorded on outcropping rock and satisfying the average spectral compatibility requirements prescribed by the Italian seismic code (NTC08). The study focuses on the territory encompassing Tuscany region in Central Italy and it has been carried out for six return periods, which are 50, 75, 101, 475, 712 and 949 years. The procedure involved four main steps: (1) grouping of the response spectra with similar features; (2) definition of the reference response spectrum for each group; (3) selection of spectrum-compatible accelerograms using the reference response spectrum of each group; and (4) linear scaling of the accelerograms to satisfy the compatibility requirement with respect to other response spectra of the group. The last step is implemented through an interactive, user-friendly program named SCALCONA 2.0, which provides the seismic input in agreement with the site location and return period specified by the user. The program is freely available at the following web site: http://www.rete.toscana.it/sett/pta/sismica/01informazione/banchedati/input_sismici/progettazione/index.htm.


      PubDate: 2014-08-16T22:30:50Z
       
  • Undrained behaviour of two silica sands and practical implications for
           modelling SSI in liquefiable soils
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Domenico Lombardi , Subhamoy Bhattacharya , Masayuki Hyodo , Takashi Kaneko
      The aim of the present study is twofold. Firstly, the paper investigates the undrained cyclic and post-cyclic behaviour of two silica sands by means of multi-stage cyclic triaxial tests. Secondly, based on the post-cyclic response observed in the element test, the authors formulate a simplified stress–strain relationship that can be conveniently used for the construction of p–y curves for liquefiable soils. The multi-stage loading condition consists of an initial cyclic loading applied to cause liquefaction, followed by undrained monotonic loading that aimed to investigate the post-cyclic response of the liquefied sample. It was found that due to the tendency of the liquefied soil to dilate upon undrained shearing, the post-liquefaction strain–stress response was characterised by a distinct strain–hardening behaviour. The latter is idealized by means of a bi-linear stress–strain model, which can be conveniently formulated in terms of three parameters, i.e.: (i) take-off shear strain, γ to , i.e. shear strain required to mobilize 1kPa of shear strength; (b) initial secant shear modulus, G 1, defined as 1/γ to ; (c) post-liquefied shear modulus at large strain, G 2 (γ⪢γ to ). Based on the experimental results, it is concluded that these parameters are strongly influenced by the initial relative density of the sample, whereby γ to decreases with increasing relative density. Differently both shear moduli (G 1 and G 2) increases with increasing relative density. Lastly, the construction of new p–y curves for liquefiable soils based on the idealized bi-linear model is described.


      PubDate: 2014-08-16T22:30:50Z
       
  • Liquefaction resistance of Babolsar sand reinforced with randomly
           distributed fibers under cyclic loading
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): R. Noorzad , P. Fardad Amini
      This research explores the performance of randomly distributed fibers in enhancing the liquefaction resistance and shear modulus of loose and medium dense sand deposits. Thirty stress-controlled cyclic triaxial tests were performed on saturated samples with and without reinforcements under undrained conditions. The effect of parameters such as fiber content, fiber length, relative density and confining pressure on liquefaction behavior of unreinforced and reinforced specimens was studied. Test results indicated that the fiber inclusions significantly increased liquefaction resistance of sand specimens. Upon increasing the fiber content and fiber length, the number of loading cycles leading to liquefaction increased. The reinforcement effect in medium dense samples was found to be more significant than that of looser samples. Further, the confining pressure had a considerable effect in reducing the liquefaction susceptibility. Shear modulus of unreinforced and reinforced samples was also evaluated; the results revealed that the shear modulus increases with increasing fiber content.


      PubDate: 2014-08-16T22:30:50Z
       
  • Dynamic Reissner–Sagoci problem for a transversely isotropic
           half-space containing finite length cylindrical cavity
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Azizollah Ardeshir-Behrestaghi , Morteza Eskandari-Ghadi , Bahram Navayi neya , Javad Vaseghi-Amiri
      A transversely isotropic linear elastic half-space containing a circular cylindrical cavity of finite length with a depth-wise axis of material symmetry is considered to be under the effect of a mono-harmonic torsional motion applied on a rigid circular disc with the same radius of the cavity and welded at the bottom of the cavity. With the aid of Fourier sine and cosine integral transforms, the mixed boundary value problem is reduced to a generalized Cauchy singular integral equation for the unknown shear stress. The Cauchy integral equation involved in this paper is analytically investigated such that the solution is written in the form of a known singular function multiplied by an unknown regular function. The regular part of the shear stress is numerically determined with the use of Gauss–Jacobi integration formula. Series representation of the stress and displacement are obtained, and it is shown that their degenerated form to the static problem of isotropic material is coincide with the existing solutions in the literature. To investigate the effects of material anisotropy and the length of cavity, the tangential displacement and the shear stress in between the rigid disc and the bottom of cavity are numerically evaluated and illustrated, where some differences are distinguished. With the differences illustrated in this paper for different length of cavity, it is recognized that the effect of length of cavity cannot be neglected in analysis and design. Different results for different degrees of anisotropy shows that the anisotropy of the material is a normal behavior, which should be considered in this kind of medium.


      PubDate: 2014-08-12T22:14:39Z
       
  • Winkler model for dynamic response of composite caisson–piles
           foundations: Seismic response
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Rui Zhong , Maosong Huang
      A simplified method with a dynamic Winkler model to study the seismic response of composite caisson–piles foundations (CCPF 1 1 CCPF: composite caisson–piles foundation. ) is developed. Firstly, with the dynamic Winkler model, the kinematic response of the CCPF subjected to vertically propagating seismic S-wave is analyzed by coupling the responses of caisson part and pile part. Secondly, a simplified model for the foundation–structure system is created with the structure simplified as a lumped mass connected to the foundation with an elastic column, and through the Fast Fourier Transformation (FFT) this model is enabled to solve transient seismic problems. Thirdly, the proposed method for the seismic response of CCPF-structure systems is verified by comparison against 3D dynamic finite element simulation, in which the Domain Reduction Method (DRM 2 2 DRM: Domain Reduction Method. ) is utilized. Lastly, the mechanism and significance of adding piles in improving the earthquake resistance of the foundation and structure is analyzed through an example with different soil conditions. Discovered in this study is that adding piles under the caisson is an efficient way to increase seismic resistant capability of the soil–foundation–structure system, and the main mechanism of that is the elimination of the pseudo-resonance.


      PubDate: 2014-08-12T22:14:39Z
       
  • Displacement-based seismic design of hysteretic damped braces for
           retrofitting in-plan irregular r.c. framed structures
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Fabio Mazza
      A displacement-based design procedure is proposed for proportioning hysteretic damped braces in order to attain, for the in-plan least seismic capacity direction and a specific level of seismic intensity, a designated performance level of a reinforced concrete (r.c.) irregular framed building to be retrofitted. To this end, a computer code for the nonlinear static analysis of spatial frames is developed to obtain the pushover curve for an assigned in-plan direction of the seismic loads. The town hall of Spilinga (Italy), a two-storey r.c. framed structure with an L-shaped plan built at the beginning of the 1960s, has been considered as case study. Four alternative structural solutions are examined, derived from the first one by the insertion of hysteretic damped braces, considering: the extended N2 and the extended pushover methods combined with a proportional and an inversely proportional in-plan stiffness distributions of hysteretic damped braces. To check the effectiveness and reliability of the design procedure, the nonlinear static response of the unbraced and damped braced frames is compared for different in-plan directions of the seismic loads. Frame members are simulated with a lumped plasticity model, including a flat surface modeling of the axial load-biaxial bending moment elastic domain, while the behavior of a hysteretic damped brace is idealized through the use of a bilinear law. Vulnerability index domains are adopted to estimate the directions of least seismic capacity at the ultimate (i.e. life-safety and collapse prevention) limit states prescribed by Italian and European seismic codes.


      PubDate: 2014-08-12T22:14:39Z
       
  • Scattering and diffraction of earthquake motions in irregular, elastic
           layers, II: Rayleigh and body P and SV waves
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): V.W. Lee , W.Y. Liu , M.D. Trifunac , N. Orbović
      We present our study of the wave propagation in an irregularly layered, elastic wave-guide excited by incoming Rayleigh surface waves and P and SV body waves. Our aim is to show examples of applying a method that will make it possible to analyze the distribution and amplification of displacements, rotations, curvatures, strains, and stresses on or below the ground surface during passage of strong earthquake ground motion. We employ the weighted-residuals method, which makes it possible to calculate the scattered and diffracted waves, and then we illustrate the amplification of motions in the vicinity of inhomogeneity.


      PubDate: 2014-08-12T22:14:39Z
       
  • Numerical validation of analytical solutions and their use for
           equivalent-linear seismic analysis of circular tunnels
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): S. Kontoe , V. Avgerinos , D.M. Potts
      The first part of this paper presents an extensive validation of four analytical solutions for the seismic design of circular tunnels. The validation is performed with a quasi-static finite element (FE) model which conforms to the assumptions of the analytical solutions. Analyses are performed for a wide range of flexibility ratios, slippage conditions at soil–lining interface, assuming both drained and undrained behaviour. Based on the numerical predictions the relative merits of the considered analytical solutions are discussed and recommendations are given for their use in design. The second part of this paper explores the use of equivalent linear soil properties in analytical solutions as an approximate way of simulating nonlinearity. The results of equivalent linear site response analyses are used as an input for the analytical solutions. The comparison of the analytical predictions with nonlinear numerical analysis results is very satisfactory. The results of this study suggest that analytical solutions can be used for preliminary design using equivalent linear properties and the corresponding compatible strain as an approximate way of accounting for nonlinear soil response.


      PubDate: 2014-08-02T21:20:48Z
       
  • An optimization method for the generation of ground motions compatible
           with multi-damping design spectra
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Zhijun Dai , Xiaojun Li , Chunlin Hou
      For some crucial engineering projects, a compatible time history of ground motions is required as a loading input for seismic dynamic analysis. The compatibility with multi-damping design spectra is critical to make sure the high reliability of analysis results. In previous methods, ground motions were hard to be tuned highly compatible with multi-damping design spectra. Hence we propose a method to optimize the compatibility of a seed ground motion history, which is either obtained from actual seismic records or generated from previous methods, by superimposing adjusted ground motions in the time domain through the L ∞ norm minimization. The optimization process makes the influences of the superimposed ground motions to the response spectra be under control by constraining objective variables. The high precision of the method is demonstrated by a concrete example, in which the max difference between the response spectra of the optimized ground motions and the design spectra for RG1.60 data [1] is 5.06% under five different damping ratios, and all response spectra envelope the design spectra.


      PubDate: 2014-08-02T21:20:48Z
       
  • A strain-based procedure to estimate strength softening in saturated clays
           during earthquakes
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Chi-Chin Tsai , Lelio H. Mejia , Philip Meymand
      Cyclic softening and strength loss of saturated clays during earthquakes is often an important consideration in engineering problems such as slope stability, dam/levee safety, and foundation bearing capacity. This study proposes a simplified procedure for evaluating cyclic softening (amount of strength loss) that may be expected in saturated clays during earthquakes and illustrates how to implement it in engineering analysis. The procedure has two main steps: (1) estimation of an equivalent cyclic shear strain amplitude and associated number of cycles induced in the soil mass by an earthquake; and (2) estimation of softening and strength loss in the soil mass. A key aspect of the proposed procedure is adoption of a strain-based approach to estimate cyclic softening as opposed to the widely used stress-based approach of liquefaction assessments. A threshold strain concept originating from the strain-based approach is first discussed and the development of a procedure is presented subsequently. The proposed procedure provides reasonable, first-order estimates of cyclic softening consistent with the other developed procedures. In addition, the capability of the procedure is demonstrated with two case histories identified as involving cyclic softening of clays.


      PubDate: 2014-08-02T21:20:48Z
       
  • The numerical and empirical evaluation of chimneys considering soil
           structure interaction and high-temperature effects
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): R. Livaoglu
      During the past strong ground motions, chimneys constructed according to international standards are representative of similar structures at industrial areas throughout the world, including those collapsed or moderately damaged in earthquake-prone regions. This is due to the specialty of structural characteristics and the special loads acting on the structure such as earthquakes, wind and differences in the level of temperature, etc. In this context, the researchers and designers should focus on the dynamic behavior of chimneys especially under high temperature and seismic effects. For this purpose, the main focus of this study is to evaluate the dynamic response of a chimney under the above-mentioned effects considering soil-structure interaction (SSI). A 52m steel chimney in Yeşilyurt township of Samsun City in Turkey was studied. The in-situ model testing and numerical models were compared. Before the commissioning of the chimney, a series of tests was realized to define its dynamic characteristics in case of no-heat and after the fabric got to work, the same tests were repeated for the same sensor locations to understand the heat effect on the dynamic response of the chimney. The ambient vibration tests are proven to be fast and practical procedures to identify the dynamic characteristics of those structures. The dynamic testing of the towers promises a widespread use, as the identification of seismic vulnerability of such structures becomes increasingly important. The data presented in this study are considered to be useful for the researchers and engineers, for whom the temperature and SSI effects on steel chimneys are a concern. Using the modal analysis techniques, presented finite element simulation for the soil/pile foundation-chimney interaction system is verified. The results of modal analyses using numerical solutions are shown to have acceptable accuracy compared with results obtained by in-situ test. The present study also aims to provide designers with material examples about the influence of these on the seismic performance of steel chimneys by means of reflecting the changes in the dynamic behavior.


      PubDate: 2014-08-02T21:20:48Z
       
  • Effects of soil–structure interaction on seismic base isolation
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): J. Enrique Luco
      The effects of soil–structure interaction on the performance of a nonlinear seismic base isolation system for a simple elastic structure are examined. The steady-state response of the system to harmonic excitation is obtained by use of the equivalent linearization method. Simple analytical expressions for the deformation of the base isolation system and of the superstructure at resonance are obtained in terms of an effective replacement oscillator characterized by amplitude-dependent frequency, damping ratio, and excitation. Numerical results suggest that the seismic response of a structure resting on an inelastic base isolation system may be larger when the flexibility of the soil is considered than the corresponding response obtained by ignoring the effects of soil–structure interaction. It is shown that, in the undamped case and in the absence of soil–structure interaction effects, a critical harmonic excitation exists beyond which the steady-state resonant response of the isolators and structure become unbounded.


      PubDate: 2014-08-02T21:20:48Z
       
  • Out-of-plane (SH) soil-structure interaction: Semi-circular rigid
           foundation revisited
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Thang H. Lee , Vincent W. Lee
      The model studied in this paper presents an extension of previous work for a shear wall on a semi-circular rigid foundation in an isotropic homogeneous and elastic half-space. The objective is to develop a soil-structure interaction model that can later be applied to the case of a flexible foundation. As shown in the Introduction below, Luco considered the case of a rigid foundation subjected to vertical incident plane SH waves, and Trifunac extended the solution for the same rigid foundation subjected to SH waves but for arbitrary angles of the incidence. In this paper, a new approach and model are presented for the same semi-circular rigid foundation with a tapered-shape (instead of rectangular) superstructure. The analytical expression for the deformation of the semi-circular rigid foundation below this tapered shear wall with soil-structure interaction in an isotropic homogeneous and elastic half-space is thus derived. Results are then compared with those of Trifunac discussed in the section below. This problem formulation can and will later be extended in the case of a flexible foundation that is semi-circular or arbitrarily shaped.


      PubDate: 2014-08-02T21:20:48Z
       
  • Experimental study on the dynamic behavior of laterally loaded single pile
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Masoud Hajialilue-Bonab , Daniel Levacher , Jean-Louis Chazelas , Amir M. Kaynia
      To improve the understanding of soil–pile interaction under horizontal dynamic loads and seismic events, a parametric centrifugal study was undertaken. Flexible piles with pile caps of different masses and instrumented with 20 strain gauges on the length of the pile were used for this purpose. The piles were impacted by a new horizontal impact device and the resulting displacement and acceleration for different levels of force were measured. The inherent basic parameters of soil–pile-interaction have been evaluated. An analysis of the damping in relation with depth and during vibration of pile is carried out. The equation of the movement of a beam equivalent to the pile under dynamic loading has been established and all the terms of this equation was determined using the experimental results. It shows that the value of internal damping of pile compared to other terms in the equation is insignificant. The term of inertia was divided into two parts, one related to the mass of the pile and the other related to the mass of the associated soil. The contribution of each term to the equation at different periods (or time of) of vibration was illustrated. Distribution versus time of the displacements and the reactions of the soil at any depth were deduced from the profiles of the bending moments by a double integration and a double derivation respectively. Then the dynamic P–y curves or loops were constructed based on these results. A static test has been performed with the same pile installed in the same conditions so that to obtain the static P–y curves. The procedures of experimental tests and P–y curves construction are explained and a comparison between static and dynamic P–y curves is also indicated.


      PubDate: 2014-08-02T21:20:48Z
       
  • Earthquake ground motion predictive equations for Garhwal Himalaya, India
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Ashish Harbindu , Sushil Gupta , M.L. Sharma
      Predictive equations based on the stochastic approach are developed for earthquake ground motions from Garhwal Himalayan earthquakes of 3.5≤M w ≤6.8 at a distance of 10≤R≤250km. The predicted ground motion parameters are response spectral values at frequencies from 0.25 to 20Hz, and peak ground acceleration (PGA). The ground motion prediction equations (GMPEs) are derived from an empirically based stochastic ground motion model. The GMPEs show a fair agreement with the empirically developed ground motion equations from Himalaya as well as the NGA equation. The proposed relations also reasonably predict the observed ground motion of two major Himalayan earthquakes from Garhwal Himalayan region. For high magnitudes, there is insufficient data to satisfactorily judge the relationship; however it reasonably predicts the 1991 Uttarkashi earthquake (M w =6.8) and 1999 Chamoli earthquake (M w =6.4) from Garhwal Himalaya region.


      PubDate: 2014-08-02T21:20:48Z
       
  • Scoping prediction of re-radiated ground-borne noise and vibration near
           high speed rail lines with variable soils
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): D.P. Connolly , G. Kouroussis , P.K. Woodward , A. Giannopoulos , O. Verlinden , M.C. Forde
      This paper outlines a vibration prediction tool, ScopeRail, capable of predicting in-door noise and vibration, within structures in close proximity to high speed railway lines. The tool is designed to rapidly predict vibration levels over large track distances, while using historical soil information to increase accuracy. Model results are compared to an alternative, commonly used, scoping model and it is found that ScopeRail offers higher accuracy predictions. This increased accuracy can potentially reduce the cost of vibration environmental impact assessments for new high speed rail lines. To develop the tool, a three-dimensional finite element model is first outlined capable of simulating vibration generation and propagation from high speed rail lines. A vast array of model permutations are computed to assess the effect of each input parameter on absolute ground vibration levels. These relations are analysed using a machine learning approach, resulting in a model that can instantly predict ground vibration levels in the presence of different train speeds and soil profiles. Then a collection of empirical factors are coupled with the model to allow for the prediction of structural vibration and in-door noise in buildings located near high speed lines. Additional factors are also used to enable the prediction of vibrations in the presence of abatement measures (e.g. ballast mats and floating slab tracks) and additional excitation mechanisms (e.g. wheelflats and switches/crossings).


      PubDate: 2014-07-28T20:51:35Z
       
  • Time-harmonic response of transversely isotropic multilayered half-space
           in a cylindrical coordinate system
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Zhi Yong Ai , Zhi Xiong Li
      With the aid of the analytical layer-element method, a comprehensive analytical derivation of the response of transversely isotropic multilayered half-space subjected to time-harmonic excitations is presented in a cylindrical coordinate system. Starting with the governing equations of motion and the constitutive equations of transversely isotropic elastic body, and based on the Fourier expansion, Hankel and Laplace integral transform, analytical layer-elements for a finite layer and a half-space are derived. Considering the continuity conditions on adjacent layers׳ interfaces and the boundary conditions, the global stiffness matrix equations for multilayered half-space are assembled and solved. Finally, some numerical examples are given to make a comparison with the existing solution and to demonstrate the influence of parameters on the dynamic response of the medium.


      PubDate: 2014-07-28T20:51:35Z
       
  • Collapse of Showa Bridge during 1964 Niigata earthquake: A quantitative
           reappraisal on the failure mechanisms
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): S. Bhattacharya , K. Tokimatsu , K. Goda , R. Sarkar , M. Shadlou , M. Rouholamin
      Collapse of Showa Bridge during the 1964 Niigata earthquake has been, over many years, an iconic case study for demonstrating the devastating effects of liquefaction. Inertial forces during the initial shock (within the first 7s of the ground shaking) or lateral spreading of the surrounding ground (which started at 83s after the start of the shaking) cannot explain the failure of Showa Bridge as the bridge failed at about 70s following the main shock and before the lateral spreading of the ground started. In this study, quantitative analysis is carried out for various failure mechanisms that may have contributed to the failure. The study shows that at about 70s after the onset of the earthquake shaking, the increased natural period of the bridge (due to the elongation of unsupported length of the pile caused by soil liquefaction) tuned with the period of the liquefied ground causing resonance between the bridge and the ground motion. This tuning effect (resonance) caused excessive deflection at the pile head, resulting in unseating of the bridge deck from the supporting pier and thereby initiating the collapse of the bridge.


      PubDate: 2014-07-28T20:51:35Z
       
  • SSI in steel frames subjected to near-fault earthquakes
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): G. Minasidis , G.D. Hatzigeorgiou , D.E. Beskos
      Modern seismic codes are usually associated with far-field earthquakes and generally neglect soil–structure interaction, assuming that omission of this phenomenon leads to conservative results. This study investigates the effect of soil–structure interaction on the inelastic response of two-dimensional steel frames subjected to near-fault earthquakes, which have been recorded near to seismic faults with reverse and strike–slip mechanisms. In order to achieve this, thirty-six planar moment resisting steel frames which have been designed for seismic and vertical loads according to European codes are examined under the action of sixty near-fault pulse-like records. Simplified soil–structure interaction is carried out using springs and dashpots to simulate the flexibility of soil at the soil–foundation interface and adopting the effective properties of soil. Seismic response parameters, such as, interstorey drift ratios, maximum floor accelerations and inelastic displacement ratios are numerically determined by dynamic inelastic analyses. After a comprehensive statistical analysis, empirical expressions for these parameters in terms of the number of storeys of structures, the type of fault mechanism as well as the consideration or not of soil–structure interaction are obtained. Critical examination of the results indicates that the flexibility of soil strongly affects the seismic response of steel frames. Furthermore, it is concluded that the structural response parameters under consideration are noticeably influenced by the type of fault mechanism.


      PubDate: 2014-07-28T20:51:35Z
       
  • Effect of dynamic soil–bridge interaction modeling assumptions on
           the calculated seismic response of integral bridges
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Semih Erhan , Murat Dicleli
      In this study, the effect of soil–structure modeling assumptions and simplifications on the seismic analyses results of integral bridges (IBs) is investigated. For this purpose, five structural models of IBs are built in decreasing levels of complexity starting from a nonlinear structural model including close numerical simulation of the behavior of the foundation and backfill soil and gradually simplifying the model to a level where the effect of backfill and foundation soil is totally excluded. Nonlinear time history analyses of the modeled IBs are then conducted using a set of ground motions with various intensities representing small, medium and large intensity earthquakes. The analyses results are then used to assess the effect of modeling complexity level on the calculated seismic response of IBs. The nonlinear soil-bridge interaction modeling assumptions are found to have considerable effects on the calculated seismic response of IBs under medium and large intensity earthquakes.


      PubDate: 2014-07-28T20:51:35Z
       
  • A numerical study on the 2D behavior of clayey basins
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): H. Khanbabazadeh , R. Iyisan
      In this numerical study the effects of basin edge on the dynamic behavior of the clayey basins are investigated. For this purpose a range of bedrock inclinations at the valley sides from slighter 10° and 20° to steeper 30° and 40°, and three types of stiff, medium plasticity and soft clay materials are selected. The results of the 2D analyses show that not only the amplification pattern of different clay types is different, but also it differs for each material type under different motion intensities. Also, the frequency domain results show that different parts of the valleys are sensitive to different periods. It was seen that under two-dimensional conditions the amplification of clay types other than soft clay could be higher. Finally, the results of this research show the important effect of motion intensity on the 2D behavior of valleys.


      PubDate: 2014-07-28T20:51:35Z
       
  • Centrifuge modeling of interaction between reverse faulting and tunnel
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Mohammad Hassan Baziar , Ali Nabizadeh , Chung Jung Lee , Wen Yi Hung
      In this study, a series of centrifuge tests, modeling reverse fault rupture with 60° dip angle, were conducted in a dry sandy soil with a tunnel embedded in the soil layer. The test results showed that the tunnel and soil responses depended on the tunnel position, soil relative density and tunnel rigidity. Tunnels appeared be able to deviate the fault rupture path, while this deviation may be associated with significant rotation and displacement of the tunnel. However, a deeper tunnel was able to diffuse the shear deformation to a wider zone with an unsmooth surface displacement which may cause severe damage to the surface structures. Finally, the tunnel rotation, the location of the fault outcropping, the vertical displacement of the ground surface, the effect of tunnel rigidity on fault rupture path and surface displacement and the effect of soil relative density on fault–tunnel interaction were reported and discussed in this study.


      PubDate: 2014-07-28T20:51:35Z
       
  • Effect of non-plastic silt content on the liquefaction behavior of
           sand–silt mixture
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Mohammad Emdadul Karim , Md. Jahangir Alam
      To identify the effect of non-plastic silt on the cyclic behavior of sand–silt mixtures, total sixty undrained cyclic triaxial stress-control tests were carried out on sand–silt mixtures. These tests were conducted on specimens of size 71mm diameter and 142mm height with a frequency of 1Hz. Specimens were prepared at a constant relative density and constant density approach. The effect of relative density, confining pressure as well as magnitude of cyclic loading was also studied. For a constant relative density (Dr=60%) the effect of limiting silt content, pore pressure response and cyclic strength was observed. The rate of generation of excess pore water pressure with respect to cycles of loading was found to initially increase with increase in silt content till the limiting silt content and thereafter it reverses its trend when the specimens were tested at a constant relative density. The cyclic resistance behavior was observed to be just opposite to the pore pressure response. Permeability, CRR and secant shear modulus decreased till limiting silt content; after that they became constant with increasing silt content.


      PubDate: 2014-07-28T20:51:35Z
       
  • Identification of the structural model and analysis of the global seismic
           behaviour of a RC damaged building
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Antonio Di Cesare , Felice Carlo Ponzo , Marco Vona , Mauro Dolce , Angelo Masi , Maria Rosaria Gallipoli , Marco Mucciarelli
      The study of the structural behaviour of damaged RC buildings during ground motion is a fundamental topic in the modern earthquake engineering. Many studies have been carried out in order to better understand the real evolution of the damage in RC buildings during a seismic event. In this work, a damaged RC building has been intensively investigated in terms of materials property and stiffness evolution in order to interpreting the structural and nonstructural surveyed damage. The peculiarity of this building is its damage sequence during the 2002 Molise earthquake. In fact, the town of Bonefro suffered moderate damage (MCS intensity VII), with the exception of the investigated reinforced concrete building. The October 31, 2002 event (M=5.4) caused some structural damage to this building. The second event (M=5.3), on November 1, 2002, increased substantially the damage level (grade 4 according to the 1998 European Macroseismic Scale). It occurred just while, due to fortuitous circumstances, a 5min. seismic velocimetric recording was being taken. The working group has performed some frequency analyses based on the recording. Several non linear models have been defined to understand the damage evolution of the building and the local and global damage patterns through for static analyses. Finally, linear and non linear models have been developed with the main goal of identifying the characteristics of a reliable undamaged structural model.


      PubDate: 2014-07-28T20:51:35Z
       
  • Prediction of ground motion due to the collapse of a large-scale cooling
           tower under strong earthquakes
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Feng Lin , Hongkui Ji , Yinan Li , Zhaoxia Zuo , Xianglin Gu , Yi Li
      The ground motion owing to the collapse of a large-scale cooling tower under strong earthquakes was appropriately predicted using a comprehensive approach. The predicted results can be used for the safety evaluation of nuclear-related facilities adjacent to the cooling tower as well as in the planning of nuclear power plant construction in China. In this study, a cooling tower–soil model was first developed based on a falling weight–soil model, which the authors verified by falling weight tests. Then the collapse process of a cooling tower was simulated, and the collapse-induced ground vibrations were assessed by using the proposed model. Finally, the ground motion, which was a combination of the earthquake-induced ground motion and the collapse-induced ground vibrations, was estimated based on the superposition principle of waves. It was found that the cooling tower may collapse under strong earthquakes with the peak ground accelerations (PGAs) in the range of 0.35–0.45g in x (EW) and y (NS) directions, respectively. These PGAs are far beyond the PGA range of major earthquakes in the common seismic design in China. The types of the site geologies of towers can significantly affect the collapse-induced ground vibrations. For a typical hard soil consisting of strongly weathered sandy slate, moderate ground vibrations may occur in the considered region. The collapse-induced PGAs were in the range of 0.017–0.046g for the observed points at distances of 350m in radial direction. For a rock-like foundation, the collapse-induced radial PGAs may be as high as 0.08g at distances of 350m, indicating that the effect of the collapse-induced ground vibrations on the nuclear-related facilities should be seriously assessed in certain scenarios.


      PubDate: 2014-07-28T20:51:35Z
       
  • Development of a seismic risk mitigation methodology for public buildings
           applied to the hospitals of Basilicata region (Southern Italy)
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): A. Masi , G. Santarsiero , L. Chiauzzi
      This paper deals with the development of a procedure aimed at defining a seismic risk mitigation strategy for public buildings in terms of prioritization, time required and funds. The procedure is based on a global risk index involving the entire building stock under study thus facilitating an examination of risk variation over time up to its final value. Relationships between the current seismic capacity–demand ratios and the required strengthening costs (cost models) have been developed. Each of the assumed cost models has a different target in terms of capacity–demand ratio to be obtained after strengthening, basically ranging between full retrofit and upgrading. The procedure has been applied to 69 hospital buildings located in Basilicata region for which the vulnerability data was available as a result of a large assessment program set up by the regional government. Priorities have been defined on the basis of seismic capacity, local hazard and number of human beings possibly involved (exposure). The results of different strengthening strategies have been outlined with a special focus on the pros and cons of the upgrading strategy with respect to various retrofit strategies. The procedure may be applied to different categories of public buildings by properly modifying some input parameters and partially redefining criteria for prioritization.


      PubDate: 2014-07-28T20:51:35Z
       
  • Predictive model of Arias intensity and Newmark displacement for regional
           scale evaluation of earthquake-induced landslide hazard in Greece
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Konstantinos Chousianitis , Vincenzo Del Gaudio , Ioannis Kalogeras , Athanassios Ganas
      Defining the possible scenario of earthquake-induced landslides, Arias intensity is frequently used as a shaking parameter, being considered the most suitable for characterising earthquake impact, while Newmark׳s sliding-block model is widely used to predict the performance of natural slopes during earthquake shaking. In the present study we aim at providing tools for the assessment of the hazard related to earthquake-induced landslides at regional scale, by means of new empirical equations for the prediction of Arias intensity along with an empirical estimator of coseismic landslide displacements based on Newmark׳s model. The regression data, consisting of 205 strong motion recordings relative to 98 earthquakes, were subdivided into a training dataset, used to calculate equation parameters, and a validation dataset, used to compare the prediction performance among different possible functional forms and with equations derived from previous studies carried out for other regions using global and/or regional datasets. Equations predicting Arias intensities expected in Greece at known distances from seismic sources of defined magnitude proved to provide more accurate estimates if site condition and focal mechanism influence can be taken into account. Concerning the empirical estimator of Newmark displacements, we conducted rigorous Newmark analysis on 267 one-component records yielding a dataset containing 507 Newmark displacements, with the aim of developing a regression equation that is more suitable and effective for the seismotectonic environment of Greece and could be used for regional-scale seismic landslide hazard mapping. The regression analysis showed a noticeable higher goodness of fit of the proposed relations compared to formulas derived from worldwide data, suggesting a significant improvement of the empirical relation effectiveness from the use of a regionally-specific strong-motion dataset.


      PubDate: 2014-07-28T20:51:35Z
       
  • Epistemic uncertainty in on-site earthquake early warning on the use of
           PGV–PD3 empirical models
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): J.P. Wang , Yih-Min Wu
      From the literature, we found that PGV–PD3 regressions for on-site earthquake early warning (EEW) can be quite different depending on the presumption whether or not PGV–PD3 data from different regions should be “mixable” in regression analyses. As a result, this becomes a source of epistemic uncertainty in the selection of a PGV–PD3 empirical relationship for on-site EEW. This study is aimed at examining the influence of this epistemic uncertainty on EEW decision-making, and demonstrating it with an example on the use of PGV–PD3 models developed with data from Taiwan, Japan, and Southern California. The analysis shows that using the “global” PGV–PD3 relationship for Southern California would accompany a more conservative EEW decision-making (i.e., early warning is activated more frequently) than using the local empirical model developed with the PGV–PD3 data from Southern California only. However, the influence of this epistemic uncertainty on EEW is not that obvious for the cases of Taiwan and Japan.


      PubDate: 2014-07-28T20:51:35Z
       
  • A regional near-surface high frequency spectral attenuation (kappa) model
           for northwestern Turkey
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Aysegul Askan , Fatma Nurten Sisman , Onur Pekcan
      One approach to model the high-frequency attenuation of spectral amplitudes of S-waves is to express the observed exponential decay in terms of Kappa (κ) factor [1]. Kappa is a significant parameter used for identifying the high-frequency attenuation behavior of ground motions as well as one of the key parameters for stochastic strong ground motion simulation method. As of now, there is not a systematic investigation of the Kappa parameter based on the recently-compiled Turkish ground motions. In this study, we examine a strong ground motion dataset from Northwestern Turkey with varying source properties, site classes and epicentral distances. We manually compute κ from the S-wave portion of each record and study both horizontal and vertical kappa values. We use traditional regression techniques to describe the (potential) relationships between kappa and selected independent variables such as the site class, distance from the source or magnitude of the event. A linear effect of magnitude on kappa is not found statistically significant for the database studied herein. We express the initial findings of a regional κ model for Northwestern Turkey as a function of site class and epicentral distances. Single station analyses at selected sites confirm the regional model. Finally, we present stochastic strong motion simulations of past events in the region using the proposed kappa model. Regardless of the magnitude, source-to-site distance and local site conditions at the stations, the high-frequency spectral decay is simulated effectively at all stations considered.


      PubDate: 2014-07-28T20:51:35Z
       
  • Wave propagation in semi-infinite media with topographical irregularities
           using Decoupled Equations Method
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): M.I. Khodakarami , N. Khaji
      In this paper, a novel semi-analytical method, called Decoupled Equations Method (DEM), is presented for modeling of elastic wave propagation in the semi-infinite two-dimensional (2D) media which are involved surface topography. In the DEM, only the boundaries of the problem are discretized by specific subparametric elements, in which special shape functions as well as higher-order Chebyshev mapping functions are implemented. For the shape functions, Kronecker Delta property is satisfied for displacement function. Moreover, the first derivatives of displacement function with respect to the tangential coordinates on the boundaries are assigned to zero at any given node. Employing the weighted residual method and using Clenshaw–Curtis numerical integration, coefficient matrices of the system of equations are transformed into diagonal ones, which leads to a set of decoupled partial differential equations. To evaluate the accuracy of the DEM in the solution of scattering problem of plane waves, cylindrical topographical features of arbitrary shapes are solved. The obtained results present excellent agreement with the analytical solutions and the results from other numerical methods.


      PubDate: 2014-07-28T20:51:35Z
       
  • Stochastic dynamic stiffness of a surface footing for offshore wind
           
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): M.J. Vahdatirad , L.V. Andersen , L.B. Ibsen , J.D. Sørensen
      The purpose of this study, which concerns the stochastic dynamic stiffness of foundations for large offshore wind turbines, is to quantify uncertainties related to the first natural frequency of a turbine supported by a surface footing and to estimate the low event probabilities. Herein, a simple model of a wind turbine structure with equivalent coupled springs at the base is calibrated with the mean soil property values. A semianalytical solution, based on the Green׳s function for a layered half-space is utilized for estimation of foundation responses. Soil elastic modulus and layer depth are considered as random variables with lognormal distributions. The uncertainties are quantified, and the estimation of rare events of the first natural frequency is discussed through an advanced reliability approach based on subset simulation. This analysis represents a first step in the estimation of the safety with respect to the failure of a turbine in the fatigue limit state.


      PubDate: 2014-07-28T20:51:35Z
       
  • Numerical modeling on vibroflotation soil improvement techniques using a
           densification constitutive law
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Susana López-Querol , Jaime Peco , Juana Arias-Trujillo
      The densification phenomenon in dry or completely drained sands mainly occurs when these materials are subjected to dynamic loadings. This fact induces a reduction of voids volume and consequently the compaction of the soil. The Generalized Endochronic densification law, formulated in cylindrical coordinates, has been used in a finite element model for simulating vibroflotation soil improvement techniques. The effects of vibrations at a point inside the soil mass, like those applied in vibroflotation treatment, are reproduced with this code. Absorbing boundary conditions are established at those borders where spatial domain finishes, aiming to avoid spurious, artificial reflections of stress waves, which otherwise come into the domain, disturbing the computed results. A mean densification function is defined for each spatial domain, to evaluate the effect of this technique, and also employed to optimize the distance between vibration points. This is a new rational design approach, which represents a step forward development if it is compared with the usual empirical employed procedures.


      PubDate: 2014-07-28T20:51:35Z
       
  • Scattering and diffraction of earthquake motions in irregular elastic
           layers, I: Love and SH waves
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): V.W. Lee , W.Y. Liu , M.D. Trifunac , N. Orbović
      We describe the wave propagation through an irregularly layered, elastic medium for incoming body (SH) and surface (Love) waves. As a result of irregular geometry, each layer generates additional waves by scattering and diffraction. These additional waves modify the input motions and locally may lead to larger motions and concentrations of stresses, strains, and rotations on or below the ground surface. For engineering design, and in particular for analyses of soil-structure interaction, it is important to understand the nature and the consequences of such motions. The scattering and diffraction of Love and SH waves by irregular layers will be investigated by the weighted-residuals method. The scattered and diffracted mode shapes and spectral amplification characteristics at different frequencies will be examined and discussed.


      PubDate: 2014-07-28T20:51:35Z
       
  • Liquefaction-induced deformation of earthen embankments on non-homogeneous
           soil deposits under sequential ground motions
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Manika Maharjan , Akihiro Takahashi
      Damage of embankments during earthquakes is widely attributed to the liquefaction of foundation soil. Previous studies have investigated the dynamic response of embankments by mainly considering uniform sand foundation and a single earthquake event. However, the foundation of an embankment consists of many sublayers of soil from liquefiable sand to relatively impermeable layer, and during earthquakes a mainshock may trigger numerous aftershocks within a short time which may have the potential to cause additional damage to soil structures. Accordingly, the investigation of liquefaction-induced deformation of earthen embankments on various liquefiable foundation conditions under mainshock–aftershock sequential ground motions is carried out by a series of dynamic centrifuge tests in this study. The liquefiable foundation includes uniform sand profile, continuous layered soil profile, and non-homogeneous soil profiles. Effects of various foundation conditions on embankment deformations are compared and analyzed. From the test results, it is found that the embankment resting on non-homogeneous soil deposits suffer more damage compared to the uniform sand foundation of same relative density. The test results also suggest that the sequential ground motions have a significant effect on the accumulated deformation of embankment.


      PubDate: 2014-07-28T20:51:35Z
       
  • Seismic performance of circular RC bridge columns with
           flexure–torsion interaction
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Piguang Wang , Qiang Han , Xiuli Du
      Reinforced concrete (RC) bridge columns for skewed, curved bridges and other kinds of irregular bridges can be subjected to combined loadings with axial load, shear force, flexure and torsion under multi-dimensional earthquake excitations. Combined loadings including torsion probably affect the seismic performance of these bridge columns. The experimental investigation on the seismic performance of circular RC bridge columns under combined cyclic bending and torsional loading is conducted in this paper. Twelve circular RC bridge column specimens are tested under various loading conditions: cyclic bending, cyclic torsion, and combined cyclic torsion and cyclic bending. Several combinations of cyclic bending and cyclic torsion are applied to evaluate the interaction between torsion and flexural capacity of bridge columns. The experimental results showed that the flexural capacity decreases and the damage tends to occur upward outside the flexural plastic hinge region as the level of applied cyclic torsion increases, and the torsional capacity decreases as the level of applied cyclic bending increases. The failure mode and deformation characteristics of RC bridge columns will be changed due to the effect of combined flexural and torsional loadings. The locking and unlocking effect of the spiral reinforcement on torsional and flexural envelopes of columns under pure torsion and combined cyclic bending and torsion is found. The influence of aspect ratio, longitudinal reinforcement ratio and type of spiral reinforcement on the seismic performance of columns under combined action with the same rotation-drift ratio is also discussed. An empirical flexural and torsional hysteretic model for circular RC columns with single spiral stirrup under combined cyclic bending and torsion is proposed based on the experimental results.


      PubDate: 2014-07-28T20:51:35Z
       
  • Centrifuge modeling of the seismic responses of sand deposits with an
           intra-silt layer
    • Abstract: Publication date: October 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 65
      Author(s): Chung-Jung Lee , Huei-Tsyr Chen , Hon-Chen Lien , Yu-Chen Wei , Wen-Yi Hung
      Three dynamic centrifuge model tests were conducted at an acceleration of 80g to simulate the seismic responses of level sand deposits: an intra-silt layer was embedded in two of these sand deposits at different depths. The effects of a low-permeability intra-silt layer on the build-up and dissipation of excess pore-water pressure, surface settlement, and the related liquefaction mechanism were investigated. An intra-silt layer modifies the seismic response of the sand deposit, reduces the extent of liquefaction, and thus decreases surface settlement. The depth of the intra-silt layer is one of the factors influencing the seismic responses of the sand deposits. The magnitude of the surface settlement is proportional to the degree of liquefaction in the sand deposit. The high positive hydraulic gradients appearing in both the intra-silt layer and in the sand deposit lying on the intra-silt layer can break a thinner or weaker top layer and result in sand boiling. Our visual animation of the ratio of the excess pore-water pressure and the lateral displacement revealed that the liquefaction front travels upward during shaking and the solidification front travels upward after shaking.


      PubDate: 2014-07-28T20:51:35Z
       
  • Analysis of damage data of low-rise buildings subjected to a shallow Mw6.3
           earthquake
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Bjarni Bessason , Jón Örvar Bjarnason , Ari Guðmundsson , Júlíus Sólnes , Scott Steedman
      In May 2008 a shallow Mw6.3 earthquake struck South Iceland with an epicentre close to two small towns. Nearly 5000 low-rise residential buildings were affected. The recorded maximum PGA was 0.88g. A great deal of damage occurred, but there was no loss of life. In Iceland all buildings are registered in a detailed official database and insurance against natural disasters is obligatory. As the repair costs for every affected building had to be assessed for insurance purposes this provided an unusual opportunity to review structural performance across the whole population of buildings in the affected area. The estimated repair cost was classified in a number of subcategories covering structural and non-structural damage for five different residential building typologies. Study of these buildings showed that non-structural damage dominated the overall damage. The main monetary damage was cosmetic damage of partition walls and flooring. The structural systems performed quite well and no buildings collapsed.


      PubDate: 2014-07-28T20:51:35Z
       
  • Correlation between seismic parameters of far-fault motions and damage
           indices of low-rise reinforced concrete frames
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Vui Van Cao , Hamid Reza Ronagh
      The aim of this paper is to present the results of an investigation on the degree of correlation that exists between several available seismic parameters of far-fault ground motions and the structural damage under earthquake in low-rise reinforced concrete buildings. The results show that Velocity Spectrum Intensity is the leading parameter exhibiting the strongest correlation, followed by Housner Intensity and Spectral Acceleration. Interestingly, six of the very commonly used seismic parameters demonstrate poor correlations with the damage of such structures. The results also show the existence of a very weak correlation (far behind many other seismic parameters) between the conventionally used parameter Peak Ground Acceleration and the damage (either expressed through the damage index or the inter storey drift).


      PubDate: 2014-07-28T20:51:35Z
       
  • Influence of cyclic loading history on small strain shear modulus of
           saturated clays
    • Abstract: Publication date: November 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 66
      Author(s): Chuan Gu , Jun Wang , Yuanqiang Cai , Lin Guo
      Small strain shear modulus G max is an essential parameter in soil dynamics, and it is usually estimated based on the Hardin and Richart equation. However, many previous researches on sands have indicated that the Hardin and Richart equation does not consider the influences of cyclic loading history on G max. In this paper, effects of cyclic loading history on G max of saturated clays under undrained conditions are studied using a combination device of piezoelectric-ceramic bender element system and cyclic triaxial apparatus. The dynamic pre-loading includes both relatively high amplitudes of cyclic stresses and cyclic strains. G max without cyclic loading history is also investigated for the comparison purpose. Test results show that, at the same effective stress, both cyclic strain history and cyclic stress history will induce reduction of G max compared to the corresponding G max values with non-cyclic loading effects. In strain-controlled tests, the reduction of G max is slight and relatively stable; while in stress-controlled tests, the reduction of G max increases suddenly and remarkably when the effective stresses degrade to a certain degree. The comparison between double amplitude axial strain and residual excess pore water pressure behaviors show that the remarkable reduction of G max can demonstrate the cyclic failure of saturated clays.


      PubDate: 2014-07-28T20:51:35Z
       
 
 
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