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  Subjects -> EARTH SCIENCES (Total: 636 journals)
    - EARTH SCIENCES (462 journals)
    - GEOLOGY (68 journals)
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EARTH SCIENCES (462 journals)            First | 1 2 3 4 5     

Marine Geophysical Researches     Hybrid Journal   (Followers: 6)
Marine Georesources & Geotechnology     Hybrid Journal   (Followers: 1)
Marine Mammal Science     Hybrid Journal   (Followers: 5)
Marine Policy     Hybrid Journal   (Followers: 33)
Mathematical Geosciences     Hybrid Journal   (Followers: 3)
Mathematical Physics, Analysis and Geometry     Hybrid Journal   (Followers: 1)
Memoirs     Hybrid Journal   (Followers: 2)
Memoirs of the Association of Australasian Palaeontologists     Full-text available via subscription   (Followers: 2)
Meteoritics & Planetary Science     Hybrid Journal   (Followers: 3)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Mineralium Deposita     Hybrid Journal  
Mineralogia     Open Access   (Followers: 1)
Mineralogy and Petrology     Hybrid Journal   (Followers: 1)
Mineria y Geologia     Open Access   (Followers: 1)
Momona Ethiopian Journal of Science     Open Access   (Followers: 4)
Moscow University Geology Bulletin     Hybrid Journal  
Moscow University Physics Bulletin     Hybrid Journal  
Mountain Research and Development     Open Access   (Followers: 3)
Natural Hazards     Hybrid Journal   (Followers: 115)
Natural Hazards and Earth System Sciences (NHESS)     Open Access   (Followers: 6)
Natural Hazards Review     Full-text available via subscription   (Followers: 9)
Natural Resources Research     Hybrid Journal   (Followers: 4)
Nature Geoscience     Full-text available via subscription   (Followers: 129)
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: 6)
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: 68)
Ocean Development & International Law     Hybrid Journal   (Followers: 10)
Ocean Dynamics     Hybrid Journal   (Followers: 6)
Ocean Engineering     Hybrid Journal   (Followers: 5)
Ocean Modelling     Hybrid Journal   (Followers: 5)
Ocean Science (OS)     Open Access   (Followers: 6)
Ocean Science Discussions (OSD)     Open Access   (Followers: 5)
Ocean Science Journal     Hybrid Journal   (Followers: 3)
Open Geosciences     Open Access   (Followers: 6)
Open Journal of Earthquake Research     Open Access  
Open Journal of Soil Science     Open Access   (Followers: 5)
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)
Permafrost and Periglacial Processes     Hybrid Journal   (Followers: 3)
Pesquisas em Geociências     Open Access  
Petroleum Geoscience     Hybrid Journal   (Followers: 6)
Petrology     Hybrid Journal   (Followers: 6)
Photogrammetrie - Fernerkundung - Geoinformation     Full-text available via subscription  
Physical Geography     Hybrid Journal   (Followers: 6)
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 10)
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: 11)
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   (Followers: 1)
Pirineos     Open Access  
Planet     Open Access   (Followers: 1)
Plasma Physics and Controlled Fusion     Hybrid Journal   (Followers: 3)
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: 5)
Proceedings in Marine Science     Full-text available via subscription   (Followers: 2)
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  
Progress in Earth and Planetary Science     Open Access   (Followers: 1)
Pure and Applied Geophysics     Hybrid Journal   (Followers: 9)
Quarterly Journal of Engineering Geology and Hydrogeology     Hybrid Journal   (Followers: 5)
Quaternary Australasia     Full-text available via subscription  
Quaternary Geochronology     Hybrid Journal   (Followers: 7)
Quaternary International     Hybrid Journal   (Followers: 12)
Quaternary Research     Full-text available via subscription   (Followers: 17)
Quaternary Science Reviews     Hybrid Journal   (Followers: 15)
Radiocarbon     Open Access   (Followers: 5)
Rajshahi University Journal of Life & Earth and Agricultural Sciences     Open Access   (Followers: 1)
Raumforschung und Raumordnung     Hybrid Journal  
Remote Sensing     Open Access   (Followers: 13)
Remote Sensing Letters     Hybrid Journal   (Followers: 10)
Remote Sensing Science     Open Access   (Followers: 3)
Rendiconti Lincei     Hybrid Journal  
Reports on Geodesy and Geoinformatics     Open Access   (Followers: 1)
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   (Followers: 1)
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: 17)
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 Teledetección     Open Access  
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)

  First | 1 2 3 4 5     

Journal Cover   Soil Dynamics and Earthquake Engineering
  [SJR: 1.482]   [H-I: 45]   [8 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [2800 journals]
  • Floor response spectra of a partially embedded seismically isolated
           nuclear plant
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Ioannis Politopoulos, Ion Sergis, Fan Wang
      This paper deals with the effects of foundation embedment on the floor response spectra of big base isolated structures such as nuclear power plants. Analyses of a finite element model, representative of a real nuclear power plant, have been carried out. It has been demonstrated that, in agreement with previous work, base rocking excitation, induced by soil–structure interaction, may amplify the non-isolated modes׳ response and thus it must not be overlooked.


      PubDate: 2015-09-01T16:18:08Z
       
  • The effect of preloading on the liquefaction cyclic strength of mixtures
           of sand and silt
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): C.A. Stamatopoulos, F. Lopez-Caballero, A. Modaressi-Farahmand-Razavi
      The paper studies the effect of preloading on the liquefaction cyclic strength of silty sands in the free field condition. This effect first is investigated by cyclic shear tests where horizontal shear stress oscillated about a zero mean value. Samples with varying fines content and at varying pre-stress ratios, densities and vertical stresses are tested. Test results show a marked increase of the liquefaction cyclic strength with the pre-stress ratio. The effect is more pronounced for tests with less liquefaction cyclic strength without pre-stress. Using critical state soil mechanics concepts, factors simulating the effect of preloading on the liquefaction cyclic strength are identified and based on the results of the laboratory program an empirical expression is proposed predicting the increase in the liquefaction cyclic strength induced by pre-stress. This expression is validated by numerical simulation of the relevant laboratory tests using an elastoplastic multi-mechanism model. In addition, based on the derived expression, a methodology is proposed predicting the increase in liquefaction cyclic strength as a result of preloading in the field in the case of the free field condition. This methodology is validated by the comparison with field measurements on liquefaction-susceptible soils before and after the field application of preloading. Last but not least, the increase in liquefaction cyclic strength which the proposed methodology predicts for typical soil profiles and embankment preloads is predicted and discussed.


      PubDate: 2015-08-27T16:03:37Z
       
  • A simplified method of calculating the impedance and foundation input
           motion of foundations with a large number of piles
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Fangyuan Zhou, Xuezhang Wen, Nobuo Fukuwa, Hongping Zhu
      A new simplified method is developed for the analysis of the impedance and foundation input motion of foundations with a large number of piles. In this proposed method, the neighboring piles are replaced by a single equivalent pile. This process of replacement reduces the number of degrees of freedom, computer memory requirement, and calculation time. To validate the simplified method, the impedance and foundation input motion of a raft foundation and an embedded foundation supported by piles groups are calculated through both the simplified method and the rigorous numerical method. Results show that the proposed simplified method for the impedance and foundation input motion of a foundation with a large number of piles has sufficient accuracy and good computational efficiency.


      PubDate: 2015-08-27T16:03:37Z
       
  • Simple method for real-time seismic damage assessment of bridges
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): I. Anastasopoulos, P.Ch. Anastasopoulos, A. Agalianos, L. Sakellariadis
      Seismic damage of bridges may pose a severe threat to motorway users, and preventive closure until post-seismic inspection may be viewed as the only safe option. However, such a measure may incur pronounced losses by obstructing transportation of rescue teams. On the other hand, allowing traffic on earthquake-damaged bridges is a difficult decision with potentially dire consequences. Hence, the main dilemma for the motorway administrator is whether to interrupt the operation of the network, calling for timely development and implementation of a RApid REsponse (RARE) system. The development of such a RARE system requires an effective means to estimate the seismic damage of motorway structures in real time. This paper contributes towards such a direction by introducing a simple method for real time seismic damage assessment of motorway bridges. The proposed method requires nonlinear dynamic time history analyses using multiple seismic records as seismic excitation. Based on the results of the analyses, statistical models are estimated, and nonlinear regression equations are developed to express seismic damage as a function of statistically significant intensity measures (IMs). Such equations are easily programmable and can be employed for real-time damage assessment, as part of an online expert system. In the event of an earthquake, the nearest seismic motion(s), recorded by an online accelerograph network, will be used in real time to estimate the damage state of motorway structures, employing the developed equations. The efficiency of the proposed method is demonstrated using a single bridge pier as an illustrative example. Based on finite element (FE) analysis results, three nonlinear regression models are estimated correlating three damage indices (DIs) with statistically significantly IMs.


      PubDate: 2015-08-27T16:03:37Z
       
  • Generalized failure envelope for caisson foundations in cohesive soil:
           Static and dynamic loading
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Nikos Gerolymos, Athanasios Zafeirakos, Konstantinos Karapiperis
      The response of massive caisson foundations to combined vertical (N), horizontal (Q) and moment (M) loading is investigated parametrically by a series of three-dimensional finite element analyses. The study considers foundations in cohesive soil, with due consideration to the caisson-soil contact interface conditions. The ultimate limit states are presented by failure envelopes in dimensionless and normalized forms and the effects of the embedment ratio, vertical load and interface friction on the bearing capacity are studied in detail. Particular emphasis is given on the physical and geometrical interpretation of the kinematic mechanisms that accompany failure, with respect to the loading ratio M/Q. Exploiting the numerical results, analytical expressions are derived for the capacities under pure horizontal, moment and vertical loading, for certain conditions. For the case of fully bonded interface conditions, comparison is given with upper bound limit equilibrium solutions based on Brinch Hansen theory for the ultimate lateral soil reaction. A generalized closed-form expression for the failure envelope in M–Q–N space is then proposed and validated for all cases examined. It is shown that the incremental displacement vector of the caisson at failure follows an associated flow rule, with respect to the envelope, irrespective of: (a) the caisson geometry, and (b) the interface conditions. A simplified geometrical explanation and physical interpretation of the associativity in M-Q load space is also provided. Finally, the derived failure envelope is validated against low (0.67Hz) and high frequency (5Hz) dynamic loading tests and the role of radiation damping on the response of the caisson at near failure conditions is unraveled.


      PubDate: 2015-08-27T16:03:37Z
       
  • Structure-soil-structure interaction effects on the dynamic response of
           piled structures under obliquely incident seismic shear waves
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Guillermo M. Álamo, Luis A. Padrón, Juan J. Aznárez, Orlando Maeso
      This work studies the structure-soil-structure interaction (SSSI) effects on the dynamic response of nearby piled structures under obliquely incident shear waves. For this purpose, a three-dimensional, frequency-domain, coupled boundary element – finite element (BEM–FEM) model is used to analyse the response of a configuration of three buildings aligned parallel to the horizontal component of the wave propagation direction. The SSSI effects are studied in terms of the maximum shear force at the base of the structures in both frequency- and time-domains. The results are presented in a set of graphs so that the magnitude of the interaction effects in configurations of buildings with similar vibration properties depending on the distance between them and the angle of incidence can be easily estimated. These results show a high influence of the wave type and angle of incidence on the interaction effects, not always corresponding the worst-case scenario with the commonly assumed hypothesis of vertical incidence. It is found that for configurations of non-slender structures, the SSSI effects can significantly amplify or reduce the single building maximum response depending on the separation between structures and excitation.
      Graphical abstract image Highlights

      PubDate: 2015-08-27T16:03:37Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77




      PubDate: 2015-08-15T06:25:56Z
       
  • Seismic analysis of motorway bridges accounting for key structural
           components and nonlinear soil–structure interaction
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): I. Anastasopoulos, L. Sakellariadis, A. Agalianos
      The paper introduces an efficient methodology to analyze the seismic performance of motorway bridges. Rigorous 3D models of a typical overpass bridge are developed and used to assess the efficiency of the proposed method. Fixed-base conditions are initially considered to focus on the effect of key structural components. The proposed simplified model is composed of a SDOF system of a pier with lateral and rotational springs and dashpots connected at the top, representing the deck and the abutment bearings. Its definition requires section analysis of the pier, and computation of spring and dashpot coefficients using simple formulas. It is shown that the lateral and rotational restraint provided by the deck and the abutment bearings is not at all negligible and should be taken into account. The simplified model is extended to account for nonlinear soil–structure interaction, replacing the soil–foundation system with horizontal, vertical, and rotational springs and dashpots. While the horizontal and vertical springs and dashpots are assumed elastic, the nonlinear rotational spring is defined on the basis of non-dimensional moment–rotation relations. The simplified model compares well with the full 3D model of the bridge–abutment–foundation–soil system, and is therefore considered a reasonable approximation.


      PubDate: 2015-08-15T06:25:56Z
       
  • Framework for the derivation of analytical fragility curves and life cycle
           cost analysis for non-seismically designed buildings
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Nicholas C. Kyriakides, Christis Z. Chrysostomou, Elia A. Tantele, Renos A. Votsis
      The quantification of the devastating effects of earthquakes on buildings can be achieved with the use of earthquake risk assessment. The formulation of strategies to minimise this risk is a complex task which relies on data regarding mainly the hazard, vulnerability and remaining life of the building. In this paper, the case study of Limassol municipality is presented. Initially, the building inventory and categorisation is defined followed by the selection of hazard scenarios and the development of analytical vulnerability curves. In the final part, risk assessment is performed leading to the formulation of retrofitting strategies for long term use.


      PubDate: 2015-08-15T06:25:56Z
       
  • Effects of cyclic confining pressure on the deformation characteristics of
           natural soft clay
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Lei Sun, Chuan Gu, Peng Wang
      To investigate the coupling effects of cyclic deviator stress and cyclic confining pressure on the deformation behavior of natural soft clay under partially-drained conditions, a series of one-way cyclic triaxial tests with and without cyclic confining pressure were carried out. Test results show that, at the same amplitude of cyclic deviator stress, the increase of cyclic confining pressure amplitude will accelerate the accumulation of both permanent volumetric and axial strain significantly. The comparison between test results for different amplitudes of cyclic confining pressure shows that tests with a cyclic confining pressure corresponding to a stress path of η ampl =p ampl /q ampl =1 lead to a 1.4 times larger permanent volumetric strain and a 1.2 times larger permanent axial strain compared to the conventional cyclic triaxial tests with constant confining pressure (η ampl =1/3). In case of η ampl =2 the permanent strains are found to be even 2.0 or 1.5 times larger compared to the standard tests. Finally, an empirical formula is proposed for the prediction of permanent axial deformations of natural soft clays under partially-drained conditions, considering the effects of cyclic confining pressure.


      PubDate: 2015-08-10T06:20:08Z
       
  • Correlation of Arias intensity with amplitude, duration and cumulative
           intensity measures
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Brendon A. Bradley
      This manuscript examines the correlation of Arias intensity (AI) with nine amplitude-, duration-, and cumulative-based ground motion intensity measures. The correlations are determined using ground motions from active shallow crustal earthquakes in the NGA-West1 database, and recently developed ground motion prediction equations (GMPEs). Multiple GMPE combinations and bootstrap sampling are used to explicitly consider correlation uncertainties due to model selection and finite sample effects, respectively. It is shown that AI is highly correlated with high-frequency amplitude-based intensity measures and negatively correlated with significant duration intensity measures. AI also has a strong, but not perfect, correlation with cumulative absolute velocity ( CAV ), which is also a cumulative measure of ground motion severity. Particular attention is given to the physical interpretation of the observed correlations of AI and other intensity measures, often in comparison to those obtained with CAV . Parametric equations are developed to enable the obtained correlations to be easily used in applications such as ground motion selection and vector hazard analysis.


      PubDate: 2015-08-10T06:20:08Z
       
  • Damage prediction in RC columns under low-cyclic loading using AE
           monitoring technique
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Jianguang Yue
      A low-cyclic loading test is conducted on a reinforced concrete (RC) column until its failure with the acoustic emission (AE) technique. It ascertains that AE technique is very effective for assessing the damage of RC columns subjected to earthquake-type loadings. The test results show a strong correlation between the hysteretic strain energy and the AE energy histories. Thus, an empirical formula is proposed to predict the level of damage and the closeness to failure of RC columns on the basis of the AE energy recorded by one piezoelectric sensor located near the critical zone.


      PubDate: 2015-08-10T06:20:08Z
       
  • Microzonation of Banja Luka for performance-based earthquake-resistant
           design
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): V.W. Lee, M.I. Manić, B.Ð. Bulajić, D. Herak, M. Herak, M.D. Trifunac
      New microzonation maps for the city of Banja Luka in the Republic of Srpska in Bosnia and Herzegovina are presented based on the uniform-hazard-spectrum (UHS) methodology. The results are compared with the previous generation of microzonation maps published in the early 1970s, which were determined for the largest expected levels of shaking and for the spatial variations based on the soil site properties and the observed damage during the 1969 earthquake. The old and new methods are compared with emphasis on their role in the long-term criteria for regional earthquake-resistant design guidelines and the associated consequences.


      PubDate: 2015-08-02T03:24:20Z
       
  • Quasi-3D analysis: Validation by full 3D analysis and field tests on
           single piles and pile groups
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Guoxi Wu, W.D. Liam Finn, Jason Dowling
      A quasi-3D method for the analysis of single piles and pile groups is presented. The method includes an equivalent linear constitutive model for nonlinear analysis, an 8-node pile element that simulates the effects of pile volume and energy transmitting boundaries which are especially important for the analysis of high frequency loading of machine foundations. The quasi-3D formulation and equivalent linear model result in orders of magnitude decreases in computational time. The accuracy and reliability of the approximate approach was validated by comparing results with 3D analytical results from MIT and by data from field tests on single piles and pile groups from Taiwan. The computed results compared very favorably with the analytical and field test data.


      PubDate: 2015-08-02T03:24:20Z
       
  • Dynamic response of structures subjected to pounding and
           structure–soil–structure interaction
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): B. Madani, F. Behnamfar, H. Tajmir Riahi
      During strong earthquakes, adjacent structures with non-sufficient clear distances collide with each other. In addition to such a pounding, cross interaction of adjacent structures through soil can exchange the vibration energy between buildings and make the problem even more complex. In this paper, effects of both of the mentioned phenomena on the inelastic response of selected steel structures are studied. Number of stories varied between 3 and 12 and different clear distances up to the seismic codes prescribed value are considered. The pounding element is modeled within Opensees. A coupled model of springs and dashpots is utilized for through-the-soil interaction of the adjacent structures, for two types of soft soils. The pounding force, relative displacements of stories, story shears, and plastic hinge rotations are compared for different conditions as the maximum responses averaged between seven consistent earthquakes. As a result, simultaneous effects of pounding and structure–soil–structure interaction are discussed.


      PubDate: 2015-08-02T03:24:20Z
       
  • Phase errors in accelerometer arrays: An analysis based on collocated
           sensors and FEM
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Fanis Moschas, Dimitris Mouzoulas, Stathis Stiros
      The error properties of arrays of accelerometers were studied on the basis of systematic experiments and analysis of the differences in the recordings of collocated sensors. Four identical tri-axial force-balance accelerometers with common recordings and time stamping, were set at symmetrical positions on a prototype oscillator, a T-type inverted pendulum, and were subject to controlled excitations. Based on Finite Element Modeling (FEM) the response of the oscillator was modeled and there were identified time series of acceleration of different collocated sensors predicted to be identical (“comparable”). The differences of the corresponding “comparable” measurement time series, which are functions only of noise, were found important, indicating that the accelerometer arrays are characterized by significant dynamic noise and not by low-amplitude Gaussian noise, as is widely assumed. Further analysis of time series of accelerometer noise was based on spectral analysis techniques in the frequency and the time domain and on coherence, on filtering and on cross-correlation, as well as on examination of the impact of noise in the drift (errors computation of displacements using double numerical integration). The output of this study is that phase noise (jitter, or phase instability) characterizes accelerometers, as in the case with all other array sensors and sensor networks and this is a main source of dynamic noise. The latter becomes significant especially at the level of sampling interval (0.005sec in our experiments), characterizes strong motions, is not constant and may be regarded as instrument-specific noise. Strategies to overcome this dynamic noise important for the modeling of structural response are discussed.


      PubDate: 2015-08-02T03:24:20Z
       
  • Evaluation of 1-D seismic site response modeling of sand using centrifuge
           experiments
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Youssef M.A. Hashash, Shideh Dashti, Maria Ines Romero, Majid Ghayoomi, Michael Musgrove
      The response of an equivalent 26m-thick deposit of dry, medium-dense, Nevada Sand with a relative density of 60% is measured in the centrifuge under six 1-D, horizontal earthquake motions applied to the base of the centrifuge container. Several 1-D site response analysis techniques are employed to simulate the experiments, including (a) equivalent linear analyses, (b) nonlinear analyses using a multi-degree-of-freedom, lumped mass model, and (c) finite element analyses of a soil column using a pressure-dependent, multi-yield, plasticity soil model. An average V s profile was estimated using empirical correlations. Soil dynamic properties included published generic modulus reduction and damping curves with implied strength correction as well as recommended plasticity model parameters based on soil index properties. Computed and measured lateral displacements, accelerations, shear strains, spectral accelerations, and Arias Intensities are presented and their differences are quantified in terms of mean residuals and variance. The comparisons demonstrate that 1-D seismic site response analyses using the available strength corrected, generic, pressure-dependent modulus reduction and damping curves for medium-dense dry sand can reliably compute soil response under 1-D wave propagation using any of the three methods, with an absolute mean residual of less than 0.5.


      PubDate: 2015-08-02T03:24:20Z
       
  • Axisymmetric dynamic response of the multi-layered transversely isotropic
           medium
    • Abstract: Publication date: November 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 78
      Author(s): Pengchong Zhang, Jun Liu, Gao Lin, Wenyuan Wang
      By virtue of the precise integration method (PIM) and the technique of mixed variable formulations, solutions for the dynamic response of the multi-layered transversely isotropic medium subjected to the axisymmetric time-harmonic forces are presented. The planes of cross anisotropy are assumed to be parallel to the horizontal surface of the stratified media. Four kinds of vertically acting axisymmetric loads are prescribed either at the external surface or in the interior of the soil system. Thicknesses and number of the medium strata are not limited. Employing the Hankel integral transform in cylindrical coordinate, the axisymmetric governing equations in terms of displacements of the multi-layered media are uncoupled. Applying mixed variable formulations, more concise first-order ordinary differential matrix equations from the uncoupled motion equations can be obtained. Solutions of the ordinary differential matrix equations in the transformed domain are acquired by utilizing the approach of PIM. Since PIM is highly accurate to solve the sets of first-order ordinary differential equations, any desired accuracy of the solutions can be achieved. All calculations are based on the corresponding algebraic operations and computational efforts can be reduced to a great extent. Comparisons with the existing numerical solutions are made to confirm the accuracy of the present solutions proposed by this procedure. Several examples are illustrated to explore the influences of the type and degree of material anisotropy, the frequency of excitation and loading positions on the dynamic response of the stratified medium.


      PubDate: 2015-08-02T03:24:20Z
       
  • Centrifuge modeling of offshore wind foundations under earthquake loading
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Hao Yu, Xiangwu Zeng, Frank H. Neff, Bo Li, Jijian Lian
      The construction of large offshore wind turbines in seismic active regions has great demand on the design of foundations. The occurrence of soil liquefaction under seismic motion will affect the stability of the foundations and consequently the operation of the turbines. In this study, a group of earthquake centrifuge tests was performed on wind turbine models with gravity and monopile foundations, respectively, to exam their seismic response. It was found that the seismic behavior of models was quite different in the dry or saturated conditions. Each type of foundation exhibited distinct response to the earthquake loading, especially in the offshore environment. In the supplementary tests, several remediation methods were evaluated in order to mitigate the relatively large lateral displacement of pile foundation (by fixed-end pile and multi-pile foundation) and excessive settlement of gravity foundation (by densification, stone column, and cementation techniques).


      PubDate: 2015-07-16T21:30:56Z
       
  • Tuned mass damper effects on the response of multi-storied structures
           observed in geotechnical centrifuge tests
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): R.N. Jabary, S.P.G. Madabhushi
      Tuned mass dampers (TMDs) are widely used to reduce vibrations in structures. However, very little research is available on the experimental investigation of TMDs and their performance in soil-structure systems. In this paper, a series of geotechnical centrifuge tests was conducted to investigate the effects of TMDs on the response of a multiple-storey sway frame structure undergoing dynamic soil-structure interaction (SSI). Structural responses were recorded for a wide range of input motion characteristics, damper configurations and soil profiles. The practicality associated with the use of TMDs in the damping of resonant structures in light of unexpected earthquake characteristics different from design earthquakes was experimentally demonstrated. Tuning a TMD to soil-structure system properties rather than fixed-base structural properties was found to double the improvement in damping and reduce the original peak response by nearly half. The potential effectiveness of a de-tuned mass damper in light of significant SSI was also demonstrated.


      PubDate: 2015-07-16T21:30:56Z
       
  • Translation, torsion, and wave excitation of a building during
           soil–structure interaction excited by an earthquake SH pulse
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Vlado Gičev, Mihailo D. Trifunac, Nebojša Orbović
      A two-dimensional (2-D) model of a building supported by a rectangular, flexible foundation embedded in the soil is analyzed. The building, the foundation, and the soil have different physical properties. The building is assumed to be linear, but the soil and the foundation can experience nonlinear deformations. While the work spent for the development of nonlinear strains in the soil can consume a significant part of the input wave energy—and thus less energy is available for the excitation of the building—the nonlinear response in the soil and the foundation does not signficantly alter the nature of excitation of the base of the building. It is noted that the response of a building can be approximated by translation and torsion of the base for excitation by long, strong motion waves.


      PubDate: 2015-07-16T21:30:56Z
       
  • Attenuation zones of periodic pile barriers with initial stress
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Xinnan Liu, Zhifei Shi, Hongjun Xiang, Y.L. Mo
      Periodic pile barriers exhibit unique dynamic property, i.e., the frequency attenuation zones. When wave frequencies fall in the attenuation zones, the amplitude of the elastic waves could be reduced by the periodic pile barriers. In the present paper, out-of-plane waves propagating in two-dimensional periodic pile barriers are investigated. A novel numerical approach based on the weak form quadrature element method (WFQEM) is developed to study the effect of initial stress on the attenuation zones of the pile barriers. The proposed method is verified to be with significant advantages in both accuracy and convergence with regard to the lumped-mass method (LMM) in particular cases. The theoretical results show that the initial stress significantly alters the position and width of the attenuation zones, however, it does not affect the maximum attenuation coefficient. In addition, elastic waves propagating in periodic pile barriers with finite number of unit cells is simulated at the end of this paper. The results obtained in the present paper are very useful for the design and application of periodic pile barriers in ambient vibration reduction.


      PubDate: 2015-07-16T21:30:56Z
       
  • Seismic protection of monuments using particle dampers in multi-drum
           columns
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): A. Papalou , E. Strepelias , D. Roubien , S. Bousias , T. Triantafillou
      This paper investigates the use of innovative, cost-effective techniques to protect ancient monuments consisting of multi-drum columns from seismic excitations. The proposed approach includes the use of particle dampers in the form of classical drums, with a hollow part containing particles. These can substitute damaged or missing drums. Their effectiveness in reducing the seismic response of classical columns is examined by exciting a marble multi-drum column-model of 3m height by dynamic loads. The influence of the system parameters such as mass ratio (mass of particles with respect to mass of the column), placement of damper, particle and damper size on the effectiveness of the particle damper is also investigated. The experimental results showed that particle dampers, if properly designed, can reduce the monument׳s dynamic response by more than 30%. Finally, some brief design guidelines are given for benefiting from the use of such dampers in monumental sites.


      PubDate: 2015-07-11T12:23:53Z
       
  • Soil characteristics in Doon Valley (north west Himalaya, India) by
           inversion of H/V spectral ratios from ambient noise measurements
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): A.K. Mundepi , J.J. Galiana-Merino , A.K.L. Asthana , S. Rosa-Cintas
      Past and recent observations have shown that the local site conditions significantly affect the behavior of seismic waves and its potential to cause destructive earthquakes. Thus, seismic microzonation studies have become crucial for seismic hazard assessment, providing local soil characteristics that can help to evaluate the possible seismic effects. Among the different methods used for estimating the soil characteristics, the ones based on ambient noise measurements, such as the H/V technique, become a cheap, non-invasive and successful way for evaluating the soil properties along a studied area. In this work, ambient noise measurements were taken at 240 sites around the Doon Valley, India, in order to characterize the sediment deposits. First, the H/V analysis has been carried out to estimate the resonant frequencies along the valley. Subsequently, some of this H/V results have been inverted, using the neighborhood algorithm and the available geotechnical information, in order to provide an estimation of the S-wave velocity profiles at the studied sites. Using all these information, we have characterized the sedimentary deposits in different areas of the Doon Valley, providing the resonant frequency, the soil thickness, the mean S-wave velocity of the sediments, and the mean S-wave velocity in the uppermost 30m.


      PubDate: 2015-07-06T12:09:42Z
       
  • An elastic-wave-based full-wavefield imaging method for investigating
           defects in a high-speed railway under-track structure
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Ailan Che , Zheng Tang , Shaokong Feng
      In geotechnical engineering, defect detection for concrete structure can be simplified as a multi-layered media problem in most cases. The types of defects are mainly identified as cracks inside the concrete, interlaminar peeling, and loose bedding voids. The study of the wave propagation phenomenon in multi-scale layered media and the effects on defects merits investigation. The present research focuses first on the analysis of this phenomenon using numerical methods. The wave propagation characteristics of the multi-layered model with defects are assessed with dynamic FEM analyses under three-dimensional conditions. The analysis is obtained in the time domain and allows the consideration of multiple wave reflections between layers. Based on this analysis, a full-wavefield imaging detection method is developed and then applied to reveal the defects in the under-track structure of a high-speed railway. This testing system integrates the point-source/point-receiver scheme with the multi-directional imaging technique to achieve an effect analogous to that achieved with scanning. It is equipped with an impacting hammer, a series of three-component velocity transducers and a signal capturing unit. To evaluate the feasibility of this system for detecting defects in the under-track structure of the high-speed railway, a full-scaled high-speed railway model test with pre-setting defection is conducted. The data are analyzed according to characteristics of waveform and wave energy. The average amplitude is used to evaluate the defect area. It is concluded that the full-wavefield imaging detection method exhibits high potential for inspecting the defects of the under-track structure of high-speed railways by imaging.


      PubDate: 2015-07-06T12:09:42Z
       
  • Numerical evaluation of hydrodynamic damping due to the Upper Mounted
           Baffles in real scale tanks
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): M.A. Goudarzi , P. Farshadmanesh
      In this study, the hydrodynamic damping effects of Upper Mounted Baffles (UMB) used in the real scale liquid tanks are numerically investigated. In this regard, the paper follows three main purposes. First, the accuracy of the analytical model developed by the author is examined for full scale applications. In this regard, the tanks equipped by UMB with various dimensions and locations are numerically analyzed in free vibration mode. Then, the numerical results are compared with an analytical solution results, and the validity of the analytical formulation for using in real applications is discussed. Second, the seismic efficiency of UMB is considered, and the reduction of the sloshing wave height due to the presence of the UMB is examined under several earthquake excitations. Finally, a seismic design procedure is proposed to evaluate the effect of UMB on the suppression of sloshing in a liquid tank, and its predictions are compared with the results of numerical analysis.


      PubDate: 2015-07-06T12:09:42Z
       
  • Dynamic response of a tunnel buried in a saturated poroelastic soil layer
           to a moving point load
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Zonghao Yuan , Changjie Xu , Yuanqiang Cai , Zhigang Cao
      The dynamic response of a tunnel buried in a two-dimensional poroelastic soil layer subjected to a moving point load was investigated theoretically. The tunnel was simplified as an infinite long Euler–Bernoulli beam, which was placed parallel to the traction-free ground surface. The saturated layer was governed by Biot’s theory. Combined with the specified boundary conditions along the beam and saturated poroelastic layer, the coupled equations of the system were solved analytically in the frequency–wavenumber domain based on Fourier transform. The time domain responses were obtained by the fast inverse Fourier transform. The critical velocity of the considered structure was determined from the dispersion curves. The different dynamic characteristics of the elastic soil medium and the saturated poroelastic medium subjected to the underground moving load were investigated. It is concluded that, for coarse materials or fine materials subjected to the high-velocity loading, models ignoring the coupling effects between the pore fluid and the soil skeleton may cause errors. The shear modulus and the permeability coefficients of the saturated soil as well as the load moving velocity had significant influence on the displacement and pore pressure responses.


      PubDate: 2015-07-06T12:09:42Z
       
  • Northern Aegean Earthquake (Mw=6.9): Observations at three seismic
           downhole arrays in Istanbul
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): S.U. Dikmen , A. Edincliler , A. Pinar
      The Northern Aegean Earthquake (M w =6.9\M L =6.5) took place on May 24, 2014 between the islands of Gokceada, Turkey and Samothraki, Greece. The tremors were felt as far as in Istanbul, about 300km on the East – Northeast (ENE) side of the epicenter. Kandilli Observatory and Earthquake Research Institute (KOERI) of Bogazici University, Turkey operate three downhole arrays in Istanbul, namely Atakoy (ATK), Fatih (FTH) and Zeytinburnu (ZYT) arrays. In this study, waveforms and site response observed at the KOERI operated seismic downhole arrays during the May 2014 Northern Aegean Earthquake (NAE2014) are analyzed in detail and presented. Evaluation of the acceleration records have shown low amplitude but long period and long duration motions at Istanbul. Furthermore, the analyses of the recordings suggest that V s30 alone may not be a sufficient parameter for the characterization of site amplification.


      PubDate: 2015-07-06T12:09:42Z
       
  • Post-cyclic loading settlement of saturated clean sand
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Kenan Hazirbaba , Maksat Omarow
      Saturated sand deposits may experience significant settlement or reconsolidation with the dissipation of excess pore pressure in the post-cyclic loading phase even if liquefaction has not occurred. This paper presents results from an extensive and systematic experimental study on the factors governing the post-cyclic loading settlement of saturated clean sand. Strain-controlled, undrained, triaxial tests were performed on reconstituted specimens of Ottawa (C-109) sand. Effects of excess pore pressure, induced shear strain, consolidation stress, number of loading cycles, and relative density on post-loading settlement were investigated. It was found that the settlement potential during the post-loading phase is strongly correlated to the excess pore pressure; the larger the excess pore pressure the greater the settlement. The potential to develop excess pore pressure, however, decreases considerably with increasing consolidation effective stress in the range between 100kPa and 400kPa. Additionally, the level of induced shear strain and the number of loading cycles were confirmed to be important factors in the development of excess pore pressure and post-loading settlement. The results revealed a unique relationship between initial liquefaction and post-loading settlement. Specimens that were loaded up to initial liquefaction were found to experience about the same volumetric strain in the post-loading phase, irrespective of the induced shear strain.


      PubDate: 2015-07-06T12:09:42Z
       
  • A simplified 3 D.O.F. model of A FEM model for seismic analysis of a silo
           containing elastic material accounting for soil–structure
           interaction
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Ayşegül Durmuş , Ramazan Livaoglu
      The purpose of this study is the evaluation of dynamic behavior induced by seismic activity on a silo system, containing bulk material, with a soil foundation. The interaction effects between the silo and bulk material, as well as the effects produced between the foundation of the silo and the soil, were taken into account. Proposed simplified approximation, as well as the finite model, were used for analysis. The results, from the presented approximation, were compared with a more rigorous obtainment method. Initially, the produced simplified approximation, with elastic material assumption for the grain, could determine the pressures on the dynamic material along with displacements along the height of the silo wall and base shear force, etc., with remarkable precision. Some comparisons, via a change of soil and/or foundation conditions, were also made regarding the seismic pressure of the dynamic material pressure, displacement and base shear forces for both squat and slender silos. Comparing the analytical predictions to results from the numerical simulations produced good results. It can be concluded that the model can be used effectively to perform a broad suite of parametric studies, not only at the design stage but also as a reliable tool for predicting system behavior under the limit state of the system. The results and comprehensive analysis show that displacement effects and base shear forces generally decreased when soil was softer; however, soil structure interaction (SSI) did not have any considerable effects on squat silos and therefore need not be taken into practice.


      PubDate: 2015-07-01T13:49:11Z
       
  • Determining anti-plane responses induced by oblique-truncated semicircular
           canyon using systematic hybrid method with mapping function
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Wen-Shinn Shyu , Tsung-Jen Teng , Chuen-Shii Chou
      This paper proposes a novel strategy for the investigation of displacement amplitude ( u y ) near and along an oblique-truncated semicircular canyon subjected to shear horizontal (SH) waves. Transfinite interpolation (TFI) was used to obtain the coordinates of nodes and determine the sequence of node numbering in the inner finite region including the canyon. The hybrid method, comprising finite element method and a Lamb series, was applied in conjunction with TFI to study the effects of canyon geometry, incident angle of SH waves ( θ ), and dimensionless frequency ( η ) on u y . We detailed the amplification of u y in the illuminated zone and variations in u y due to canyon-decay-effect along the canyon surface as well as the decay of u y resulting from the shield effect in the shadow zone. Interestingly, oblique-effects play an important role in the magnification of u y along the inclined bottom of canyons, and variations in θ and η dominate the patterns of u y .
      Graphical abstract image

      PubDate: 2015-07-01T13:49:11Z
       
  • A surface seismic approach to liquefaction
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Silvia Castellaro , Riccardo Panzeri , Flaminia Mesiti , Lara Bertello
      The liquefaction potential of soils is traditionally assessed through geotechnical approaches based on the calculation of the cyclical stress ratio (CSR) induced by the expected earthquake and the ‘resistance’ provided by the soil, which is quantified through standard penetration (SPT), cone penetration (CPT), or similar tests. In more recent years, attempts to assess the liquefaction potential have also been made through measurement of shear wave velocity (V S) in boreholes or from the surface. The latter approach has the advantage of being non-invasive and low cost and of surveying lines rather than single points. However, the resolution of seismic surface techniques is lower than that of borehole techniques and it is still debated whether it is sufficient to assess the liquefaction potential. In this paper we focus our attention on surface seismic techniques (specifically the popular passive and active seismic techniques based on the correlation of surface waves such as ReMiTM, MASW, ESAC, SSAP, etc.) and explore their performance in assessing the liquefaction susceptibility of soils. The experimental dataset is provided by the two main seismic events of M L=5.9 and 5.8 (M W=6.1, M W=6.0) that struck the Emilia-Romagna region (Northern Italy) on May 20 and 29, 2012, after which extensive liquefaction phenomena were documented in an area of 1200km2. The CPT and drillings available in the area allow us to classify the soils into four classes: A) shallow liquefied sandy soils, B) shallow non-liquefied sandy soils, C) deep non-liquefied sandy soils, and D) clayey–silty soils, and to determine that on average class A soils presented a higher sand content at the depth of 5–8m compared to class B soils, where sand was dominant in the upper 5m. Surface wave active–passive surveys were performed at 84 sites, and it was found that they were capable of discriminating among only three soil classes, since class A and B soils showed exactly the same V S distribution, and it is possible to show both experimentally and theoretically that they appear not to have sufficient resolution to address the seismic liquefaction issue. As a last step, we applied the state-of-the art CSR–V S method to assess the liquefaction potential of sandy deposits and we found that it failed in the studied area. This might be due to the insufficient resolution of the surface wave methods in assessing the Vs of thin layers and to the fact that Vs scales with the square root of the shear modulus, which implies an intrinsic lower sensitivity of Vs to the shear resistance of the soil compared to parameters traditionally measured with the penetration tests. However, it also emerged that the pure observation of the surface wave dispersion curves at their simplest level (i.e. in the frequency domain, with no inversion) is still potentially informative and can be used to identify the sites where more detailed surveys to assess the liquefaction potential are recommended.


      PubDate: 2015-07-01T13:49:11Z
       
  • Vibration control of piled-structures through
           structure-soil-structure-interaction
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Pierfrancesco Cacciola , Maria Garcia Espinosa , Alessandro Tombari
      This paper deals with the vibration control of existing structures forced by earthquake induced ground motion. To this aim it is proposed for the first time to exploit the structure–soil–structure mechanism to develop a device, hosted in the soil but detached from the structure, able to absorb part of the seismic energy so to reduce the vibration of neighbourhood structures. The design of the device is herein addressed to protect monopile structures from earthquake induced ground motion. By modelling the ground motion as zero-mean quasi-stationary response-spectrum-compatible Gaussian stochastic process, the soil as visco-elastic medium and the target monopiled-structure as a linear behaving structure the device, herein called Vibrating Barrier (ViBa), has been designed through an optimization procedure. Various numerical and experimental results are produced to show the effectiveness of the ViBa. Remarkably, a significant reduction of the structural response up to 44% has been achieved.


      PubDate: 2015-07-01T13:49:11Z
       
  • A new expression for determining the bending stiffness of circular
           micropile groups
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Keyvan Abdollahi , Alireza Mortezaei
      Increased bending stiffness and decreased foundation rotation are two main factors which reduce the rocking motion of foundation. A micropile group in circular arrangement is an innovative technique for reducing the rocking motion of the foundation. In this paper, the effects of several parameters were numerically investigated on the rocking stiffness of circular micropile group foundations. The finite difference software FLAC3D was used to model the foundation, soil, and the structure. The micropiles used in this study varied in the diameter, but had similar length. A total of seven records were selected to cover a wide range of frequency content, duration and amplitude. The results from the numerical simulation were compared and verified against those obtained from an alternative numerical method as well as a set of experimental test results. The model was then used for parametric studies and the effects of relevant parameters were investigated. The results showed that slenderness, inclination angle and distance ratio of a micropile group are main factors which increase the soil stiffness and control the seismic motion of high-rise buildings. Based on the results, a new expression was proposed that can be used to determine the optimal moment of inertia of circular micropile groups. The proposed expression revealed that the primary factors which reduce the effective period of the buildings are the number, diameter, and injection pressure of micropiles in a circular micropile group. Using the proposed relationship, it was found that using circular micropile groups can reduce the destructive seismic effects (i.e. drift demand) in high-rise buildings by up to 60%.


      PubDate: 2015-07-01T13:49:11Z
       
  • Effects of site stiffness and source to receiver distance on surface wave
           tests׳ results
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Jyant Kumar , Tarun Naskar
      By using six 4.5Hz geophones, surface wave tests were performed on four different sites by dropping freely a 65kg mass from a height of 5m. The receivers were kept far away from the source to eliminate the arrival of body waves. Three different sources to nearest receiver distances (S), namely, 46m, 56m and 66m, were chosen. Dispersion curves were drawn for all the sites. The maximum wavelength (λ max ), the maximum depth (d max ) up to which exploration can be made and the frequency content of the signals depends on the site stiffness and the value of S. A stiffer site yields greater values of λ max and d max . For stiffer sites, an increase in S leads to an increase in λ max . The predominant time durations of the signals increase from stiffer to softer sites. An inverse analysis was also performed based on the stiffness matrix approach in conjunction with the maximum vertical flexibility coefficient of ground surface to establish the governing mode of excitation. For the Site 2, the results from the surface wave tests were found to compare reasonably well with that determined on the basis of cross boreholes seismic tests.


      PubDate: 2015-07-01T13:49:11Z
       
  • Cyclic and post-cyclic monotonic behavior of Adapazari soils
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Zulkuf Kaya , Ayfer Erken
      The August 17, 1999 Kocaeli earthquake affected the city of Adapazari, which is located in the northwest of Turkey, with severe liquefaction and bearing capacity failures causing tilting of buildings, excessive settlements and lateral displacements. To understand the stress–strain behavior and pore pressure behavior of undisturbed soils during the earthquake, the cyclic and post-cyclic shear strength tests have been conducted on soil samples obtained from Adapazari in a cyclic triaxial test system within the scope of this research. Cyclic tests have been conducted under stress controlled and undrained conditions. Post-cyclic monotonic tests have been conducted following cyclic tests. The strength curves obtained in the experiments showed that the dynamic resistance of silty sand was found to be 45% lower than those of high plasticity soils (MH). The strength of clayey soils with the plasticity index of PI=15–16% was lower compared to the strength of high plasticity soils. Also, it was observed that silty sand soils had the lowest strength. The dynamic strength of the soils increased with the increase in plasticity.


      PubDate: 2015-07-01T13:49:11Z
       
  • Real-valued modal response history analysis for asymmetric-plan buildings
           with nonlinear viscous dampers
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Jui-Liang Lin , Tze-How Liu , Keh-Chyuan Tsai
      Modal analysis, which is clear in concept and simple in computation, is widely applied to evaluate the seismic responses of elastic structures with proportional damping. Nevertheless, nonlinear viscous dampers commonly installed in real buildings result in non-proportionally damped structures, which impede the modal analysis in real number field for such structures. This study develops the approach of performing real-valued modal response history analysis for elastic two-way asymmetric-plan buildings with nonlinear viscous dampers. To this end, this study first constructs the nonlinear three-degree-of-freedom (3DOF) modal equations of motion for such structures. The nonlinear 3DOF modal equations of motion retain the non-proportional damping characteristics in the modal space. Hence, by solving the nonlinear 3DOF modal equations of motion, the total response history is effectively attained by arithmetically summing up the modal response histories. This study uses nine two-way asymmetric-plan buildings, each equipped with nonlinear viscous dampers subjected to three bi-directional ground motions to verify the proposed approach. The investigation results show that the proposed simplified analysis approach provides satisfactory estimation of the seismic responses of common asymmetric-plan buildings with nonlinear viscous dampers.


      PubDate: 2015-07-01T13:49:11Z
       
  • A synthetic formulation for the Italian seismic hazard and code
           implications for the seismic risk
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): I. Vanzi , G.C. Marano , G. Monti , C. Nuti
      The paper contains two parts. In the first one, the seismic hazard on the Italian territory, as given by the current Italian structural design code, published in 2008, is discussed. Hazard curves, given by the Italian code in a tabular form, are fitted with a single non-linear model and it is shown that a more compact, simple and user-ready territorial hazard description can be applied. The model is valid for both the bedrock and the surface seismic hazards, and is accurate. The surface seismic hazard is computed with a local amplification mapping, which is now well detailed over the entire territory. Departing from these results, in the second part the territorial seismic risk for the ultimate limit state is computed via a parametric fragility curve. From the results, it can be inferred that the codes need further factors calibration, with the aims of guaranteeing both territorially uniform reliability levels, and the traditionally assumed target reliability levels, e.g. those stated in the Eurocodes.


      PubDate: 2015-07-01T13:49:11Z
       
  • Seismic assessment and retrofit of two heritage-listed R/C elevated water
           storage tanks
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Claudia Mori , Stefano Sorace , Gloria Terenzi
      A seismic assessment and advanced retrofit study on two heritage-listed reinforced concrete (R/C) elevated water storage tanks is presented in this paper. The two structures were built between the late 1920s and the early 1930s as water suppliers for a coal power plant in Santa Maria Novella Station in Florence, and are still in service. The first, taller tank has a R/C frame supporting structure and is currently used as water supplier for trains and platform services. The second, shorter tank, with a shaft-shell supporting structure, is used as water tower for the Station. The dynamic behaviour of the fluid is simulated by means of a classical convective and impulsive mass model, for which a discrete three-dimensional schematization is originally implemented in the finite element analysis. The time–history assessment enquiry highlights numerical collapse of the frame structure in the taller tank, and unsafe tensile stress states in a large portion of the shaft structure of the shorter one, under seismic action scaled at the maximum considered earthquake level. Based on these results, two retrofit hypotheses are proposed, and namely a dissipative bracing system incorporating pressurized fluid viscous spring-dampers, for the taller tank, and a base isolation system including double curved surface sliders, for the shorter one. The mechanical parameters, design criteria and technical implementation details of the two rehabilitation strategies are illustrated. The verification time–history analyses in protected conditions show that a substantial enhancement of the seismic response capacities of both structures is attained as compared to their original configurations, with little architectural intrusion, quick installation works and competitive costs.


      PubDate: 2015-07-01T13:49:11Z
       
  • Engineering behavior and correlated parameters from obtained results of
           sand–silt mixtures
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Darn-Horng Hsiao , Vu To-Anh Phan , Yi-Ting Hsieh , Hsin-Yi Kuo
      The results of an experimental study on sands with low-plastic silt content are presented. Flexible wall permeameter tests, drained and undrained triaxial compression tests, one-dimensional consolidation tests, and undrained cyclic triaxial tests were performed on specimens with a low plastic silt content of 0%, 15%, 30%, 40%, 50% and 60% by weight. The soil specimens were tested under three different categories: (1) at a constant void ratio index; (2) at the same peak deviator stress in a triaxial test; and (3) at a constant relative density. The results were observed to be somewhat different from previous studies with non-plastic silt content and plastic fine content. Cyclic triaxial tests showed that an increase in silt content causes a decrease in the cyclic resistance ratio with a silt content up to 40–50% and thereafter causes an increase in the cyclic resistance ratio with further increases in silt content. The results of triaxial tests indicated that the value of the peak deviator stress changed with different types of specimens, and the greater internal friction an angle has, the stronger is the liquefaction resistance. Flexible wall permeameter tests concluded that the saturated hydraulic conductivity slowly decreases with an increase in silt content in the range from 0% to 30% and considerably decreases with a silt content greater than 30%. A one-dimensional consolidation test postulated that increasing silt content decreases the coefficient of consolidation. In addition, the global void ratio did not appear to be a pertinent parameter in explaining the behavior of sand–silt mixtures, while fine content and intergranular void ratio were suitable parameters for explaining the behavior of sand–silt mixtures. Finally, correlated parameters from obtained results were also presented in this study.


      PubDate: 2015-07-01T13:49:11Z
       
  • Characterizing the process of liquefaction initiation in Anzali shore sand
           through critical state soil mechanics
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Amirabbas Mohammadi , Abbas Qadimi
      A series of monotonic drained and cyclic undrained triaxial tests were conducted to study the cyclic behavior of a shore sand mainly formed of silica and carbonate, under critical state soil mechanics framework. The main focus of the study was on simplifying the process of approaching to liquefaction, and predicting it using the concept of “state”. The results indicated that generation of pore water pressure from the start of cycling to liquefaction can be simplified into a bilinear-shaped trend in a semi-logarithmic space. The pore pressure response, the number of cycles needed for liquefaction and the cyclic resistance ratio were shown to depend on the initial state relative to the critical state line in space of specific volume against logarithm of mean effective stress. Analysis of the results also indicated that the bilinear trend of approaching to liquefaction and the liquefaction resistance of the soil with various densities and stress levels could be well characterized in terms of the state parameter and the cyclic stress ratio, using logarithmic, exponential and quadratic formulations. Liquefaction curves were derived in terms of the state parameter, independent of soil density and stress level.


      PubDate: 2015-07-01T13:49:11Z
       
  • A note on peak accelerations computed from sliding of objects during the
           1969 Banja Luka earthquakes in former Yugoslavia
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): M.I. Manić , B.Ð. Bulajić , M.D. Trifunac
      Peak ground accelerations, computed from sliding of objects during the 1969 Banja Luka earthquakes in Bosnia and Herzegovina (former Yugoslavia) are computed assuming that the ground motion consists of simple rectangular or sinusoidal pulses. The results show good agreement with observed macroseismic estimates of shaking based on the Mercalli–Cancani–Sieberg (MCS) intensity scale. The results are also in compliance with recorded accelerations during the 1973–1986 period and with recent probabilistic hazard analyses for the Banja Luka region.


      PubDate: 2015-07-01T13:49:11Z
       
  • Determination of traffic-load-influenced depths in clayey subsoil based on
           the shakedown concept
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): LianSheng Tang , HaoKun Chen , HaiTao Sang , SiYang Zhang , JieYi Zhang
      The determination of the depth of traffic load influence is significant for pavement and embankment design on soft soil. In this study, a method based on strain-controlled criteria is presented to estimate the depths within which the behavior of a saturated clayey subsoil is affected by cyclic traffic loads. Based on the shakedown concept, the following depths of influence can be defined: (1) the threshold depth, beyond which the dynamic effect of the traffic loads is insignificant; (2) the plastic shakedown limit depth, within which the subsoil experiences noticeable and continuous deformation; and (3) the critical failure depth, within which the soil fails due to the accumulation of strain. This method for determining the depths of influence is advantageous because it is applicable to various soil types. The data required for this method consist of vertical stress responses along the soil profile and three cyclic stress limits of the soil. Based on the development of pore pressure and the dynamic strain behaviors during undrained cyclic triaxial tests, the following cyclic stress limits of the soft clay subsoil are determined: a threshold cyclic stress ratio CSRt of 0.03, a plastic shakedown limit stress ratio CSRp of 0.33 and a critical cyclic stress ratio CSRc of 0.44. These cyclic stress limits are used to determine the corresponding depths of influence, which are then used to implement ground improvements and strengthen the dynamic carrying capacity of the road structures.


      PubDate: 2015-07-01T13:49:11Z
       
  • Nonlinear incremental analysis of fire-damaged r.c. base-isolated
           structures subjected to near-fault ground motions
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Fabio Mazza
      Amplification of structural response of r.c. base-isolated structures is expected under near-fault ground motions, yet there is a lack of knowledge of their behavior in the case of fire. To investigate the nonlinear seismic response following a fire, an incremental dynamic analysis is carried out on five-storey r.c. base-isolated framed buildings with fire-protected High-Damping-Laminated-Rubber Bearings (HDLRBs), designed in line with the Italian seismic code. Horizontal components of near-fault ground motions characterized by forward-directivity or fling-step pulse-type are considered. The nonlinear seismic response of base-isolated structures in a no fire situation is compared with that in the event of fire, at 45 (i.e. R45) and 60 (i.e. R60) minutes of fire resistance, assuming both damaged (i.e. DS) and repaired (i.e. RS) stiffness conditions. Five fire scenarios are considered assuming the fire compartment confined to the area of the first level (i.e. F1), the first two (i.e. F1/2) and the upper (i.e. Fi, i=3–5) levels, with the parametric temperature–time fire curve evaluated in accordance with Eurocode 1. The nonlinear seismic analysis is performed by using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial-stress-like iterative procedure. At each step of the analysis, plastic conditions are checked at the critical (end) sections of the girders and columns, where thermal mapping with reduced mechanical properties is evaluated with the 500°C isotherm method proposed by Eurocode 2. A viscoelastic model with variable stiffness properties in the horizontal and vertical directions, depending on the axial force and lateral deformation, simulates the response of an HDLRB.


      PubDate: 2015-07-01T13:49:11Z
       
  • Seismic pressures on rigid cantilever walls retaining linear poroelastic
           soil: An exact solution
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): G.A. Papagiannopoulos , D.E. Beskos , T. Triantafyllidis
      The dynamic response of a water-saturated linear poroelastic soil layer over bedrock retained by a pair of rigid cantilever walls to a horizontal seismic excitation is obtained analytically–numerically under plane strain conditions. Hysteretic damping in the soil skeleton may also be present. The problem is solved in the frequency domain and its exact solution is obtained analytically. This is accomplished with the aid of Fourier series along the horizontal direction and solution of the resulting system of ordinary differential equations to obtain the amplitudes of the soil skeleton displacements and the pore water pressure. Soil displacements and stresses, pore water pressure as well as wall pressures and resultant forces are explicitly presented. Their variation with frequency, hysteretic damping, porosity and permeability is numerically obtained and compared against an approximate solution, to assess the degree of validity of the assumptions.


      PubDate: 2015-07-01T13:49:11Z
       
  • Ductility damage indices based on seismic performance of RC frames
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Mohammad S. Alhaddad , Khalid M. Wazira , Yousef A. Al-Salloum , Husain Abbas
      This paper presents an analytical procedure for determining ductility damage indices using static collapse mechanism analysis for ductile reinforced concrete (RC) frames subjected to prescribed drift limits corresponding to different seismic performance levels. This assessment benefits from performance-based seismic design (PBSD) concept that employs rotation ductility factors, pre-defined target damage indices and beam sidesway mechanism as key performance objectives to estimate curvature ductility demands at pre-designated plastic hinges of beam sidesway mechanism. The proposed ductility-based damage indices (DBDI) assessment procedure considers regular frames with secondary effects such as P-Delta and soil–structure interaction (SSI) within a simple non-iterative process suitable for practical applications. A 12-story RC moment frame was chosen to implement the proposed procedure considering P-Delta effect. Pushover analysis using SAP 2000 was carried out for the frame to verify the results of the DBDI method. The results show that the DBDI seismic assessment procedure can be used to quantify the damage potential at different performance levels and relate that to local flexural ductility of critical frame members. The research presented in this paper provides a simple yet conservative damage assessment tool for use by practicing engineers.


      PubDate: 2015-07-01T13:49:11Z
       
  • Experimental and numerical evaluation of the effectiveness of a stiff wave
           barrier in the soil
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): P. Coulier , V. Cuéllar , G. Degrande , G. Lombaert
      This paper discusses the design, the installation, and the experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil as a mitigation measure for railway induced vibrations. A full scale in situ experiment has been conducted at a site in El Realengo (Spain), where a barrier consisting of overlapping jet grout columns has been installed along a railway track. This barrier is stiff compared to the soil and has a depth of 7.5m, a width of 1m, and a length of 55m. Geophysical tests have been performed prior to the installation of the barrier for the determination of the dynamic soil characteristics. Extensive measurements have been carried out before and after installation of the barrier, including free field vibrations during train passages, transfer functions between the track and the free field, and the track receptance. Measurements have also been performed at a reference section adjacent to the test section in order to verify the effect of changing train, track, and soil conditions over time. The in situ measurements show that the barrier is very effective: during train passages, a reduction of vibration levels by 5dB is already obtained from 8Hz upwards, while a peak reduction of about 12dB is observed near 30Hz immediately behind the barrier. The performance decreases further away from the jet grouting wall, but remains significant. The experimental results are also compared to numerical simulations based on a coupled finite element–boundary element methodology. A reasonable agreement between experiments and predictions is found, largely confirming the initially predicted reduction. This in situ test hence serves as a ‘proof of concept׳, demonstrating that stiff wave barriers are capable of significantly reducing vibration levels, provided that they are properly designed.


      PubDate: 2015-07-01T13:49:11Z
       
  • Numerical modeling of the dynamic lateral behavior of
           geosynthetics-reinforced pile foundation system
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): Ahmed Taha , M. Hesham El Naggar , Alper Turan
      This paper presents a finite-element (FE) analysis for simulating the dynamic performance of geosynthetics-reinforced pile foundation system. The (FE) models were constructed using commercial FE program Plaxis 3D Dynamic. The numerical models were verified against the results of a reduced scale model test of geosynthetics-reinforced pile foundation system. A numerical parametric study was carried out to investigate the effect of different design parameters on the effectiveness of the proposed geosynthetics-reinforced pile foundation system. The studied parameters include: the frequency and amplitude of ground motion; the stiffness and strength of the geosynthetic reinforcement, the location of the reinforcement within the backfill material and the thickness of the backfill material. The numerical results indicated that the geosynthetics-reinforcement greatly reduced the maximum lateral acceleration response of the pile cap.


      PubDate: 2015-07-01T13:49:11Z
       
  • Bound of earthquake input energy to building structure considering shallow
           and deep ground uncertainties
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): M. Taniguchi , I. Takewaki
      The bound of earthquake input energy to building structures is clarified by considering shallow and deep ground uncertainties and soil–structure interaction. The ground motion amplification in the shallow and deep ground is described by a one-dimensional wave propagation theory. The constant input energy property to a swaying–rocking model with respect to the free-field ground surface input regardless of the soil property is used effectively to derive a bound. An extension of the previous theory for the engineering bedrock surface motion to a general earthquake ground motion model at the earthquake bedrock is made by taking full advantage of the above-mentioned input energy constant property. It is shown through numerical examples that a tight bound of earthquake input energy can be derived for the shallow and deep ground uncertainties.


      PubDate: 2015-07-01T13:49:11Z
       
  • Numerical modelling of drop load tests
    • Abstract: Publication date: October 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 77
      Author(s): R. Colombero , S. Kontoe , S. Foti , D.M. Potts
      Assessment of the attenuation of induced vibrations in the ground plays an important role in evaluating comfort and structural safety. Analytical and empirical wave attenuation relationships of increasing complexity and detail are presented in the paper, as well as a numerical model that accurately reproduces wave attenuation for a well-documented site, namely the one of the Tower of Pisa, Italy. A new source model is calibrated on near-field data and used as input for the dynamic coupled consolidation finite element analysis to achieve a satisfactory simulation. The accuracy of simpler analytical and empirical approaches is then comprehensively assessed through comparison with the validated numerical model and the field data obtained from geophones at various distances from the impact source.


      PubDate: 2015-07-01T13:49:11Z
       
 
 
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